# A Great Place To Shove Your Temperature Probe



## PistolPatch (23/2/07)

Wasn't too sure how to word this topic title but many of you will have had the same problem I'm having tonight...

*The Problem* Your tap water is around 28 degrees so that's the best you can chill to without pumps and chilled water. The best you'll chill to and this'll take 60 minutes or more is 30 degrees.

*Solutions* Well, I don't know any easy solutions. Let's talk ales... You can choose to not pitch, throw your fermenter in a 2 degree fridge and then wake up to find it's too cold the next day. You can also choose to pitch at 30 degrees, throw your fermenter in an 18 degree environment and find that it takes way too long to cool to acceptable fermentation temperatures.

If you have a temperature controller like I do (the MashMaster one - top stuff!) the real problem is where do you put the probe? If you put it in the wort which is the ideal place, and set it to say 18 degrees, your fridge will run non-stop for way too many hours - very inefficient. If you put it in the fridge set at 18 degrees then your wort is going to take forever to cool.

Being the first brew I have done in my new abode, I had to deal with this problem. The best I could cool my wort to was 30 degrees. I chose to pitch...

*So, Here is Where I Shoved My Probe Tonight* 

What I've done is shoved the Mashmaster probe half-way through the fermenter lid, set it at 18 degrees and it seems to be working a treat....

The probe, after 2.5 hours, is reading 18 degrees while the real fridge temperature is 8 degrees and the compressor is therefore not continually running....

Just pulled off 250mls of wort and it is at 24.5 degrees already.

I like that. I'm out of the danger zone.

Of course the time it takes to get down to 18 will increase exponentially but I'm happy with the above result especially as I pitched at 30. Think I can now safely put Batz's Alt to bed.

Of course pitching at the right temp would be great but tonight it wasn't an option.

My goodness! There's a movie on Channel 9 and the girl in it has taken off all her clothes.

Gotta go,
Pat

P.S. Anyone else had this problem. If so, what do you do? 

Christ! Thought it must be SBS but it is Ch 9!!!!


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## PistolPatch (23/2/07)

Just been reviewing my times whilst corresponding with brown_dog. Here's one last reading...

oil End: 9:10pm
Chill End: 10:20pm
Into Fridge: 10:45pm
First Temp Readings: 11:45am (Readings above)
Final Readings: 1:30am (As follows...)

Probe Reading = 17
Fridge Temperature = 10
Wort Temperature = 23.5

Time for bed,
Pat


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## sqyre (23/2/07)

Hey buddy looks like you and me are the only ones lurking at this time of night.

Good to see your online again.

Hows perth?



I'd just shove it in the wort..having the fridge run constantly for a while shouldn't hurt it.

I've often left the fridge door open all night after eating all the timtams in drunken stupor... and it still runs fine.

I dont think it would over-chill it either..Depends how much other stuff was in the fridge to store the cold. (if you know what i mean)



Sqyre.. :beer:


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## FNQ Bunyip (23/2/07)

I wouldent worry about it buddy, The compressor in my fermenting box has been running non stop for about 2 months now. I do trun it off for an half hour once a week to defrost the coil then straight back on . It runs so hot that I had to put an old 30cm fan blowing on the compressor to help cool it as it was seizeing up underload .. But the fan stopped that and it just runs flat out ...

Oh to build my cold room.. must go to work and earn a buck..

:beer:


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## bugwan (23/2/07)

I suspend my probe in a bottle/glass of water in the fridge. Obviously the thermal mass of the glass is smaller than the fermenter and its contents, but it's better than dangling the probe in the fridge air.

It sounds like you have found a solution, I'm a bit paranoid about sticking things directly in my wort, so I use the glass trick...


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## AUHEAMIC (23/2/07)

Hi Patch

Slightly off topic but it may help your cooling problem.

I have a similar problem with the ambient water temp in Melbourne. Although its not at 30 it takes a long time to get to a reasonable pitching temp. My solution was a pre-chiller. I put it in a 4 litre bucket, fill the bucket with water and freeze it the day before brew day. I connect it only when the wort temp is down to about 35deg as I found the ice melts pretty quickly.



Its made out of 2 metres of 3/8 soft copper and if you are careful you wont need any bending tools. You could also get away with using hose clamps instead of using welded on hose tails.

It works very well but if I made it again I would double the length of copper.


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## Ross (23/2/07)

Hi Pat,

Stick your probe in the wort, it's the best way IMHO to control your ferment accurately. Why go to all the bother of buying accurate temperature control equipment & than just measure ambient air...
You compressor will not run continually, for as the airspace cools down the fridges own thermostat will kick in intermittantly. Far better to pitch at the correct temp the following day than pitching too warm.

Bugwan - make a S/S thermowell & insert through the airlock hole of your fermenter, controlling a small bottle of water is not going to give you accurate temp control. I can ferment 2 brews in my fridge happily at temperatures 5c apart (& often do), by controling one brew & letting the other rise & fall in unison - which demonstrates the need to control the brew, not a secondary vessel...

Cheers Ross.


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## Tony (23/2/07)

I do what ross is talkind about

I have a PT100 probe that is in the firmenting wort

I use a temperature controller to switch the fridge on and off

there ia a thermostat in the fridge that is set to a relivent temp to cut out the compressor. If you dont use this the temp controller will run the fridge non stop and freeze it up.

It works a treat, holding my brews within 0.1 deg od setpoint

and it will crash chill the wort to the desired temp and them hold it there

cheers


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## Jye (23/2/07)

I second using a thermowell, dead easy to make with an old dip tube.

The next best thing would be to tape it to the side of the fermenter and then cover it with some sort of insulation so that it measures the fermenter temp and not the air.


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## therook (23/2/07)

So were in Melbourne could i get a thermowell????

and 

could this just be pushed over the Fridemate probe or would it need to be permanetly fixed some other way.

Rook


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## warrenlw63 (23/2/07)

I use two glass carboys and find it much easier to just push a bit of convoluted foam between the two carboys then push the probe into the foam against one of the carboys. Glass seems to conduct the temp quite well. Because the Fridgemate probe seems to keep identical temps to the sticky thermo on the side of the carboy.

Yep I know the temp of the fermenting wort in the carboy could be a little higher at high krausen. I sort of assume glass insulates to some degree and ferment at 2 degrees less than recommended yeast temp. Seems to work well.  

Warren -


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## warrenlw63 (23/2/07)

therook said:


> So were in Melbourne could i get a thermowell????
> 
> and
> 
> ...



Rook

Easiest way would be to get your hands on a spare corny dip tube, cut it short, beat the end down and maybe fold it over so liquid does not seep in. Even handier if you could get the tip tig welded or similar.

From what I can gather the Fridgemate probe then just pushes down the tube with a fair degree of ease.

Warren -


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## Ross (23/2/07)

therook said:


> So were in Melbourne could i get a thermowell????
> 
> and
> 
> ...



Most HBS's should be able to supply a keg diptube, which makes a perfect thermowell.
If not, send me a mail & I'll sort you out.

cheers Ross


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## Coodgee (23/2/07)

having the probe hard up against the outside of the fermenter with a rag to insulate it from the cold fridge air is accurate to within 1/2 a degree of the actual wort temperature for me.

I'm quite happy to let my ferment temp range from 17-19 degrees on a constant up and down cycle. Does anyone really think they could tell the difference between a beer fermented like this and a beer fermented at a constant 18 degrees?


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## therook (23/2/07)

No worries Ross, 

i got asked what i want for my birthday last night and the first thing i asked for was not well received  so i said i'll get some more beer stuff  

Rook


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## PistolPatch (23/2/07)

Once my wort has chilled to the correct temperature I do have my probe suspended in a dip tube in the actual wort.

The reason I didn't want to do that last night was because my fridge is a converted freezer and therefore the compressor would have run continually for about 6 hours dropping the ambient fridge temp down to about minus 25 degrees - my compressor doesn't cut out until the probe temperature matches my dialled-in temperature.

For the next brew I'll be rigging up my pond pump and using a cube of chilled water to cool for that last bit. Unfortunately last night, I didn't have the right hoses - lost in transit. This seems to work as well as a pre-chiller and I already have the gear. (Nice chiller there Peels!)

Anyway, the wort is now (at 8:30am) at 19 degrees so all is well.

And if anyone wants to know what sort of beer gets you inebriated the quickest, I'm pretty sure it's whatever beer you're having while chilling.

 
Pat


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## warrenlw63 (23/2/07)

therook said:


> the first thing i asked for was not well received



A flag for Geelong perhaps?  

Warren -


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## bindi (23/2/07)

warrenlw63 said:


> I use two glass carboys and find it much easier to just push a bit of convoluted foam between the two carboys then push the probe into the foam against one of the carboys. Glass seems to conduct the temp quite well. Because the Fridgemate probe seems to keep identical temps to the sticky thermo on the side of the carboy.
> 
> Yep I know the temp of the fermenting wort in the carboy could be a little higher at high krausen. I sort of assume glass insulates to some degree and ferment at 2 degrees less than recommended yeast temp. Seems to work well.
> 
> Warren -


 You will like this Warren, run the probe through the blow off tube into the wort for better control, I gave up on the foam taped to the side of the carboy.


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## warrenlw63 (23/2/07)

Bindi do you use a thermowell with that? If not how do you stop the wort soaking the cable?

As for taping foam to the carboy side? ... Not needed with 2 carboys. B) Just push the carboys together, stuff the foam between them and push the probe against one carboy. Easy as. The other carboy works just like a big 23 litre clamp. :super: 

Warren -


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## SpillsMostOfIt (23/2/07)

Can anyone see an issue with using aluminium tubing for a thermowell? A metre length from Bunnings costs a few dollars.

Alternatively, I guess a length of vinyl tube?


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## lonte (23/2/07)

SpillsMostOfIt said:


> Can anyone see an issue with using aluminium tubing for a thermowell? A metre length from Bunnings costs a few dollars.
> 
> Alternatively, I guess a length of vinyl tube?


the vinyl may insulate a little? The aluminium will work as good if not better than SS for temp conductivity. but it raises the age old debate of Al in beer production and alzheimers and we don't want to go there...


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## newguy (23/2/07)

lonte said:


> the vinyl may insulate a little? The aluminium will work as good if not better than SS for temp conductivity. but it raises the age old debate of Al in beer production and alzheimers and we don't want to go there...



There is really no debate.

First, when aluminum is exposed to oxygen, such as that found in ordinary air, it forms a surface oxide layer - Al2O3. This compound forms almost instantaneously, and it is chemically almost identical to ruby. Basically, unless you use an angle grinder to shower your wort with aluminum particles, no aluminum will make its way into your beer.

Second, the original study that suggested a link between aluminum and alzheimer's disease was disproven a long time ago. The study used a dye which contained aluminum to stain the slides they examined.

The only real reasons that 'big' brewers don't use aluminum equipment are because it's a soft metal and caustic cleaners will react with it. Go into any restaurant and chances are all the big stock/soup pots will be aluminum. Aluminum is safe - don't worry about it.


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## TidalPete (23/2/07)

Coodgee said:


> having the probe hard up against the outside of the fermenter with a rag to insulate it from the cold fridge air is accurate to within 1/2 a degree of the actual wort temperature for me.
> 
> I'm quite happy to let my ferment temp range from 17-19 degrees on a constant up and down cycle. Does anyone really think they could tell the difference between a beer fermented like this and a beer fermented at a constant 18 degrees?



Spot on Coodgee. :beerbang: 

:beer:


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## marky_mark (23/2/07)

I've experimented with thermowells and having my fridgemate probe strapped to the side of the fermenter, comletely insulated from the fridge air by a piece of industrial grade insulation taped over it. The problem I faced was that the wort temp would swing by a few degrees before the compressor would kick in, meaning that there would be a lot of condensation building up on the outside of the fermenter as the fridge air temp hit 15-20 C and the beer was at 10 C. For lagers I don't really want hugh temp swings at all. 

My solution was to scrap the whole insulation thing and simply use a piece of electical tape to strap the probe to the side of the fermenter. That way, the probe measures the wort temp, but is also influenced by the fridge air temp and hence will maintain very constant fermentation temperatures, down to less than a degree swing! Kind of counter intuitive to what has been discussed here but I think a valid point and somethig that took me a while to figure out. So try it guys. Just spreading the wealth of knowledge.

Cheers,

Mark


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## bindi (23/2/07)

warrenlw63 said:


> Bindi do you use a thermowell with that? If not how do you stop the wort soaking the cable?
> 
> Warren -




Waterproof cable and probe [covered in a small plastic tube just incase] <_< the chest freezer is not working as hard after the fermentation temp is reached and stable.


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## The King of Spain (23/2/07)

I just stick it to the side of the fermenter with some electrical tape - works fine.


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## oneills (23/2/07)

I'm with Mark and Deaves

I just tape the probe to the side of the fermenter with a piece of packing tape and it holds temp to within a degree using an Aldoheat temperture controller.


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## bindi (24/2/07)

oneills said:


> I'm with Mark and Deaves
> 
> I just tape the probe to the side of the fermenter with a piece of packing tape and it holds temp to within a degree using an Aldoheat temperture controller.


 I did that for a few years but a probe in the wort is so much better, I also gave away my Aldoheats [2] to new brewers [one for a fridge, the other I can't remember :unsure: ] and went digital.


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## Brad_G (24/2/07)

Hey guys, 

What a good thread. Something I have thought for ages, but didnt know whether or not to discuss it as I thought it was common knowledge. 

For interests sake, I was using a dip tube for a bit, but I didnt like the idea of something poking into my wort, so now I use electrical tape and i have not noticed a difference in my brews. I do drop the temp on my controller 1 degree though, compensation for the plastic. 

Brad


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## SpillsMostOfIt (24/2/07)

I've been vassilating between what I see are three methods - the aforementioned thermowell, taping it to the side or what I think I will probably do - making a neoprene mat which sits on the floor of my cooler and has a hole in it where the thermistor/sensor lives. The fermenter will sit on the neoprene (so it is nice and comfy) and the neoprene will effectively ensure that the temperature is very close to that of the bottom of the fermenter.

We all know/say that good temperature control is important (so there shouldn't be too much variation during fermentation), but I am guessing that the difference between temperature ranges of 16.8-18.5 and 17.0-18.0 (made-up values) is probably not going to be more/less noticeable in the end product.

Having said that, I believe that the errors in the system would be additive and most of the temperature controllers under consideration hold the temperature within a one degree range, so I can understand the desire to reduce error elsewhere.

I guess the thermal mass of multiple tens of kilograms of water makes an effective buffer, but we also are looking for two different cooling scenarios - 'Cool it down NOW!' and 'Keep it at a constant temperature'. I can't see how a simple refrigerator/freezer/cooler - using air to transfer heat - can be perfect.

But, I do have an answer for those with access to large-scale computer data centres...


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## Batz (24/2/07)

deaves said:


> I just stick it to the side of the fermenter with some electrical tape - works fine.




Same here,I use a few bits of that silver duc tape,the wide one.
Works as well as something stuck in the wort IMO,without having to have something stuck in the wort  


Batz


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## Korev (24/2/07)

I have found Blutack works well to hold the sensor on the outside of the fermentor

Peter


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## PistolPatch (25/2/07)

Great to see this got off-topic so quickly  It was meant to be about crash-chilling but now it seems to be about where to shove your probe after pitching. This getting off-topic has worked out well for me because you guys have got me thinking especially MarkyMarks post.

Lets see if I can summarise what this and subsequent posts got me thinking about

If you put your probe in the wort, like I have done, and you use a Mashmaster probe, your wort temp will cycle between, in our example of 18 degrees, 16 and 20 degrees exactly.

What MarkyMark and others are saying is that shoving your probe where I did (the airspace above the wort in the fermenter) or on the outside of the fermenter will give you lesser range, maybe even half a degree either side.

This sounds great to me and a lot easier than mucking around with the dip tubes like Ive been doing.

Have I got that summary right?

Thanks,
Pat

P.S. Please excuse my not responding to the earlier posts.


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## Ross (25/2/07)

PistolPatch said:


> What MarkyMark and others are saying is that shoving your probe where I did (the airspace above the wort in the fermenter) or on the outside of the fermenter will give you lesser range, maybe even half a degree either side.



How on earth can monitoring the airspace, give you better temp control than measuring the wort :huh: 
I'm keen to be educated B) 
My worts stay within half a degree of my set point.

cheers Ross


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## BrissyBrew (25/2/07)

Hi PistolPatch I am also selling the stainless steel probes as separate items as well.


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## Wortgames (25/2/07)

Ross, I guess it's a case of how wide of the mark your trigger points are.

If you have a controller which allows the subject to vary say 2 degrees before it activates, then having the probe in the wort would mean that the wort has varied 2 degrees before the controller responds.

If the sensor is in the airspace, then the controller will trigger more frequently as the airspace varies that 2 degrees, but the wort would presumably maintain itself at an average temperature somewhere in the middle of the range.

I guess it isn't such a big deal with narrow deadband controllers, but it might be a better way to regulate temps if you have a less precise controller.

Another issue might be that by the time the wort has registered a temp increase, the fridge has already warmed up and it will take a few minutes of chilling to chill the fridge and then the wort - by which time the wort may have warmed even more. Similarly, by the time the wort has cooled enough to turn off the controller, the fridge is probably pretty frosty, and the wort may continue chilling for a while after the controller turns off. Kind of a thermal flywheel effect.

I think it's splitting hairs really, I doubt that fluctuations in the order of a degree or two would make much difference to a brew!


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## PistolPatch (25/2/07)

Ross said:


> How on earth can monitoring the airspace, give you better temp control than measuring the wort :huh:
> I'm keen to be educated B)
> My worts stay within half a degree of my set point.
> cheers Ross



Rossco, this is the advantage of being unemployed in WA. I have the time to think through the above posts. It took me 3 days to understand the above :blink: I have no idea what to add to what Wortgames said apart from the trigger word, 'buffer.'

The air cushion acts as a buffer and this means it will cool before the wort does. This means that the wort doesn't have to cool a whole 2 degrees before the controller kicks in. Vice versa on the upside.

Bloody good idea I reckon. Takes some undistracted thought though to see the sense in it and I've got plenty!

Spot ya,
Pat

P.S. Brissy. Stainless steel probes - you champion, we need some pics!!! Throw a link in here. I have some other ideas on probes as well! Give me a few days.


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## Ross (26/2/07)

I'm not a fridgie, but my understanding was it's not a good idea to have your compressor switching on & off continually, hence the large temperature dead band in a normal fridge/freezer. If you measure the airtemp with such a tight setting, surely your fridge will be switching on/off all the time.
Measuring airspace, will not keep an active ferment at your desired temperature, submerging your probe or fixing to outside of fermenter will work much better.

Wortgames - i agree, if you have a large deadband, then measuring air temp would be better  but that's not the case with the unit we are talking about...

cheers Ross


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## bindi (26/2/07)

Ross said:


> How on earth can monitoring the airspace, give you better temp control than measuring the wort :huh:
> I'm keen to be educated B)
> My worts stay within half a degree of my set point.
> 
> cheers Ross






Ross said:


> I'm not a fridgie, but my understanding was it's not a good idea to have your compressor switching on & off continually, hence the large temperature dead band in a normal fridge/freezer. If you measure the airtemp with such a tight setting, surely your fridge will be switching on/off all the time.
> Measuring airspace, will not keep an active ferment at your desired temperature, submerging your probe or fixing to outside of fermenter will work much better.
> 
> Wortgames - i agree, if you have a large deadband, then measuring air temp would be better  but that's not the case with the unit we are talking about...
> ...




I agree with the above  stick it *in* the wort, I am a new convert to this [last few brews] and have noted that the chest freezer [ferm fridge] and controler are not working as hard IMO.


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## BrissyBrew (26/2/07)

Ross has a point about switching the compressor on and off, more switching more wear, the shorter the lifespan. That aside there are a couple of points to make.

I think the best solution varies accordingly to when we are in the fermentation cycle.

Early in the cycle I am for having a probe inside the wort, as fermentation it self generates heat. The only caveat I have with this is what that you don’t overshoot your fermentation temperature if you are crash chilling in the fridge. The easy way to get around this is to pop back and give your fermenter a rock back and forwards for the first few hours until you are close to your set fermentation temp. With your probe in the wort you will get to your fermentation temperature quicker, you just need to wait that the wort does not drop below your fermentation temp due to the buffer the wort provides. If drilling a hole in a plastic fermenter maybe offset the hole to the side may assist. You can leave your probe immersed inside the wort for the rest of the fermentation period, I do and I don’t think the two degree dead band makes a huge difference. Otherwise you could just pull the probe up a little bit so that it sits in the head space and yes the wort will be a more stable temp (excluding heat generated from the fermentation process.

Now lets say you wanting to use a controller to convert a chest freezer for wine storage (I know a few people who have done this, some of them work for the biggest wine produces in Australia). You want to keep the wine at nice stable temp and avoid any temp fluctuations. Don’t forget to cling wrap necks of the bottles, helps control humidity and keep the labels looking good. If the probe is placed in the air, even with a two degree dead band after some time the liquid in all the bottles will stabilise, you can assist this process by placing a small fan inside the freezer to make sure you have a nice even circulation of temperatures, that way you don’t get a difference between the to and the bottom of your fridge. I had been advised that the recorded variations on the temperature of the liquid in the bottles over a period of time using a data logger was less that 0.5*C (closer to 0.3*C if memory serves me right).


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## Darren (26/2/07)

Hey,

I would have thought that if your probe was in the wort you would also need to have the cooling mechanism in the wort too.

Putting your probe in the wort is stupid. It creates an additional infection risk but mainly, how long would the fridge have to be running to cool/warm the wort to the desired temp? Your fridge would get to 4 degrees fairly quickly if you needed to drop your wort tem (in the centre I presume) by 2 degrees. How do you off-set that cool fridge interior.

For a lager, I can see that in the wort may have its benefits. For an ale though, it is a waste of time. You are better off maintaining a constant fridge temp by placing the probe outside as it is all usually fermented in less than the time it takes to cool a few degrees.

cheers

Darren


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## Ross (26/2/07)

Darren said:


> Hey,
> 
> I would have thought that if your probe was in the wort you would also need to have the cooling mechanism in the wort too.
> 
> ...



I refuse to bite.... Do whatever floats your boat  

cheers Ross


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## BrissyBrew (26/2/07)

Darren said:


> ...I would have thought that if your probe was in the wort you would also need to have the cooling mechanism in the wort too....
> ...Putting your probe in the wort is stupid. It creates an additional infection risk
> Darren


If air surrounds your fermenter you have 360 degrees coverage.

As far as infection goes, the probe is a single piece of stainless steel, a quick spray of idophor (or your fav. sanitising solution) before insertion that that's it, I think the additional risk is is minimal to say the least.

I should dig it up but somebody logged a brew with three data loggers, one outside the fridge, one inside air temp and one inside the wort. What I did remember is in early fermentation wort temperature was 8*C above the air temp.


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## PostModern (26/2/07)

Think about a non-modified fridge. It's thermostat is in the airspace, not in your bottle of milk. Do normal fridges cycle too often?

I keep my fermentation probe in the airspace. I subscribe to the theory as discussed above, that the thermal mass of the wort will keep it within a degree of the set temperature most of the time. A probe in wort would have to be set with <1 degree of variance. 

Here's the scenarios:
a) *Probe in wort.*(or taped to side of fermenter) Temp set to 17 with 2 degrees variation (ie compressor cuts in when temp is 19 and out when 15). This means your wort will slowly vary between 20 and about 14, because the coolness of the fridge will keep chilling the wort even when the compressor has cut out, and when it cuts in, the temp will keep rising at least a degree before it starts dropping. Moreso with early fermentation.


b ) *Probe in air space* Temp set to 16 with 2 degrees variation. The wort will reach about 19 before the probe reads 18 and kicks in the compressor. The compressor will then chill the air space to 14 before cutting out. The thermal mass of the wort will prevent it dropping this cool, maybe 16 before it stabilises with the air temperature then the exothermic behaviour of the fermentation will start the cycle again.

I like b best.  I set the temp to two degrees cooler than I want the fermentation to be. With the probe in the wort, you have to shift the temperature of the whole mass of the wort. The compressor will run for longer, and the variation in the wort's temperature will be greater. If you set the variation to be one degree instead of 2 or three, the compressor will cycle more often, creating the exact problem you sought to avoid.

I'm not religious about this, tho. If someone could convince me of the merits of attaching the probe to the wort (or using an internal sensor), I'd change what I do, but I think my theory is sound.


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## bindi (26/2/07)

BrissyBrew said:


> I should dig it up but somebody logged a brew with three data loggers, one outside the fridge, one inside air temp and one inside the wort. What I did remember is in early fermentation wort temperature was 8*C above the air temp.



I placed 2 probes with the new brew, one taped on the outside and one in the wort, and after 12 hours there was a 5c gap still.


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## newguy (26/2/07)

I don't think there's a completely foolproof (i.e. 'correct') method of tightly controlling the temperature of fermenting beer no matter whether the probe actually contacts the beer or just the air in the fridge/freezer.

I designed and built my own HERMS (heat exchanging recirculating mashing system) and I can tell you from experience that a simple thermostatic (on/off) control action leads to overshoot/ringing of the temperature of the mash, and I'm very skeptical that beer in a fridge would be any different. The problem with thermostatic control is that it ignores the rate of change of temperature. An analogy would be driving your car to a cliff without going over it: if your approach speed is slow, chances are that simply taking your foot off the gas will allow the car to stop before it gets to the edge. Conversely, if you approach the cliff at 100 km/h, you'd have to take your foot off the gas much sooner to avoid catastrophe. What about brakes? In the thermal system of a refrigerator and the beer, there are no brakes. In this example, brakes = heater, gas pedal = cooling system.

I grossly underestimated the thermal mass/thermal momentum issue when I first put together my system and implemented a very simple modified thermostatic control algorithm. When I tested it, the system was so unstable as to be completely useless. I had to implement a much more complex PID (proportional-integral-derivative) control algorithm. PID control, in and of itself, isn't that hard to implement. The real bugger is tuning the system so that it displays optimal (i.e. no overshoot) temperature control.

The real issue is varying the cooling/heating 'power' as required. With an electric heating element, this is easily achieved by cycling the power to vary the 'on' time in relation to the 'off' time. With a fridge/freezer, good luck. It's either on or off, not in between.

Although I'm not a pro brewer, I know a few and have toured their breweries. I can assure you that their temperature control of most of their fermenters is analogous to the probe measuring the air temperature inside the fridge, not measuring the temperature of the beer. With ales anyway. The fermentation room is usually kept at a preset temperature, and they usually don't measure the temperature of the beer. Just like a giant fridge. If they ferment lagers in the same fermentation room as their ales, that fermenter will likely have a glycol jacket cooling system.


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## Screwtop (26/2/07)

Time to set the cat among the pidgeons. 

What about the location of the probe in the wort, and stratification. Does fermentation activity (CO2 production) move the wort around or do the bubbles move freely without disturbing the equilibrium of temperature stratification in the wort. Would naturally occuring layers in wort be difused by CO2 bubbles transversing such a layer. Would thermal convection play a part, would inversion layers or capping inversion layers occur, maintaining temperature stratification. Would CO2 bubbles travel more slowly through the more dense lower temperature layers and faster through the warmer layers. Air in the fridge is going to be cooler at the bottom of the cabinet than at the top, temperature of the air effects the temperature of the fermenter and the temperature of the fermenter effects the temperature of the wort, and vice versa. There is an equal and opposite reaction occuring continuously at the interface of each element and within the mass of each element, parts of the fermenter mass will be at different temperatures, but will be attempting to reach equilibrium. The air (inside and outside the fridge cabinet), fermenter material and wort, will all be effecting each other, how can such a system ever reach equilibrium when the one and only element we have control of (inside fridge air temp) is being controlled by an astable system (refrigeration system), simply incapable of maintaining a static temperature setting. In an attempt to reach equilibrium each element will affect the other, this effect occurs in both directions as physics dictates. 

I have put all of this stuff in the IBU (interesting but useless) category and simply use a probe in the airspace. No matter what measures are taken, wort temp will fluctuate and vary at differing points throughout the wort. Is it more important to measure the wort temp at the bottom (for bottom fermenting yeasts)? or the top (top fermenting yeasts)? or should the average of temps taken in varying locations in the wort be used?

I'M SO CONFUSED, think I'll have another beer and see if I can reach equilibrium :chug: ,would only make a poofteenth of a difference anyway.


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## warrenlw63 (26/2/07)

:lol: :lol: What a thread this one's turning into.

Anybody would think some of you blokes are fermenting hectolitres rather than 23 litres. :blink: 

I just stick my probe between the two fermenters with some convoluted foam. Beer tastes fine. Question you've got to ask yourselves collectively is this... Is there a problem with the finished beer in terms of bad fermentation byproducts? If not then what difference does it make where your probe is, so long as some basic stable temp control occurs it's all good. :beerbang: 

Edit: For the anal among us perhaps a rectal probe is in order?

Warren -


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## Wortgames (26/2/07)

Does measuring the temperature change it?

The application of quantum thermodynamics in fermentation, love it :beer:

Regarding the stratification - a fermenting wort heaves and rolls like you wouldn't believe, apparently it depends more on fermenter geometry than anything else. I doubt stratification would be an issue at all, especially in the volumes we are dealing with.

If you've got the technology and you can be bothered, then a probe in the wort with a suitably accurate controller is probably a slightly better way to do it, although the more 'thermal mass' you have between the chilling or heating mechanism and the probe (ie the fridge + the air + the fermenter + thermal gain due to insulation inefficiency + the wort) the slower the cycling and the greater the amount of overshoot. With a 2-stage controller this could lead to the heating and cooling systems actually fighting each other.

Personally I monitor the air temp in a commercial (fan-assisted) fridge, it just seems easiest and I believe it does the trick. In the future (if and when my fermenters are stainless) I may attach a probe to the outside of the fermenter, but I don't think I'd bother immersing a probe - I just don't really see it making enough of a difference to justify the inconvenience (small though it may be) of having something else to clean and sanitise and connect up and get in the way etc etc etc.


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## jupiter (26/2/07)

i have two thermocouples in my fridge space, 1 measuring inside air temperature, the other is taped to the side of the fermenter with a 1cm2 piece of adhesive copper tape with a 4cm2 piece of adhesive aluminium tape over the top and a big strip of gaffer tape over the top to strap it all on and support the thermocouple wire.

my temperature controller uses the taped thermocouple to control the compressor. i found using the air temperature thermocouple to control temperature, the compressor cycled on and off frequently and the fermenter temperature was dependent on the rate of fermentation and the fermenter sat at an approximate average 3degC above the inside fridge air temperature.

i was initially considering sticking a probe into the wort, but that quickly landed in the too hard basket (too much effort for little return).


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## SpillsMostOfIt (26/2/07)

I think this thread is becoming a bit like some of the sanitation threads that have come and gone. My only (current) question on both issues remains 'How did they get by 300 years ago?'. (Apart from the issue of having to walk tens or hundreds of miles to find other brewers to argue with.) Either they ditched a lot of beer or they had something right that we, collectively (or is it just me), are missing?


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## bindi (26/2/07)

SpillsMostOfIt said:


> I think this thread is becoming a bit like some of the sanitation threads that have come and gone. My only (current) question on both issues remains 'How did they get by 300 years ago?'. (Apart from the issue of having to walk tens or hundreds of miles to find other brewers to argue with.) Either they ditched a lot of beer or they had something right that we, collectively (or is it just me), are missing?




They only brewed during the right season and unlike us did not try and brew a Lager in Queensland during summer, or for that matter most Ales.  
Like trying to grow rice and cotton [Cubby Station and others] in a dry land <_< wait a sec, the silly pr$cks a doing just that . h34r:


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## Ross (26/2/07)

SpillsMostOfIt said:


> I think this thread is becoming a bit like some of the sanitation threads that have come and gone. My only (current) question on both issues remains 'How did they get by 300 years ago?'. (Apart from the issue of having to walk tens or hundreds of miles to find other brewers to argue with.) Either they ditched a lot of beer or they had something right that we, collectively (or is it just me), are missing?



Even far less than 300 years ago - The 1st brews in Australia were all brewed without fermentation control, & pretty disgusting they were too by all accounts.
++
The forum is for discusing opinions, facts & ideas, without discussion the forum would be boring. A thread like this can be of interest to quite a few, with new ideas learnt. From what I've read above, many seem happy with measuring air & are no doubt happy with their results, & as some have mentioned, a small difference in temp will probably not make much difference anyway. Others like myself who have actually measured the difference, have seen it can vary more than we are happy with & hence we prefer to measure the wort either by probe or stuck to the fermenter. If the threads of interest, you read & make your own judgement - If it's of no interest, then simple to ignore.  

Cheers Ross


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## SpillsMostOfIt (26/2/07)

Ross said:


> The 1st brews in Australia were all brewed without fermentation control, & pretty disgusting they were too by all accounts.



Were they CUB products?


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## Wortgames (26/2/07)

Brewers of old used to throw away A LOT of beer. Before they began to figure out yeast in the eighteen-wotsits it was all voodoo and luck.

In fact, the Pilsner Urquell brewery was created as a community facility when all of the local breweries had to dump barrels full of undrinkable beer leaving the villagers with no grog.


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## Screwtop (26/2/07)

Wortgames said:


> Brewers of old used to throw away A LOT of beer. Before they began to figure out yeast in the eighteen-wotsits it was all voodoo and luck.
> 
> In fact, the Pilsner Urquell brewery was created as a community facility when all of the local breweries had to dump barrels full of undrinkable beer leaving the villagers with no grog.




Lot to be said for a modified practice of old "making a starter". If the beer (starter) is good then go for it and make more wort to add. Was only the small infected (proof) batches that were thrown out.


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## BrissyBrew (26/2/07)

PostModern said:


> Here's the scenarios:
> a) *Probe in wort.*(or taped to side of fermenter) Temp set to 17 with 2 degrees variation (ie compressor cuts in when temp is 19 and out when 15). This means your wort will slowly vary between 20 and about 14, because the coolness of the fridge will keep chilling the wort even when the compressor has cut out, and when it cuts in, the temp will keep rising at least a degree before it starts dropping. Moreso with early fermentation.
> b ) *Probe in air space* Temp set to 16 with 2 degrees variation. The wort will reach about 19 before the probe reads 18 and kicks in the compressor. The compressor will then chill the air space to 14 before cutting out. The thermal mass of the wort will prevent it dropping this cool, maybe 16 before it stabilises with the air temperature then the exothermic behaviour of the fermentation will start the cycle again.
> 
> I'm not religious about this, tho. If someone could convince me of the merits of attaching the probe to the wort (or using an internal sensor), I'd change what I do, but I think my theory is sound.


SCENARIO A
Probe Inserted in Wort.

Small fan to circulate air inside the fridge/freezer unit.
Set temp 17*C
Unit will turn the compressor on when the wort hits 19*C
Unit will turn the compressor off when the wort hits 16*C

The air temperature of the fridge responds quickly if a fan is inside the unit, so when it kicks in the cooling effect will be reasonably immediate. With a fan running in the unit you are also adding a little bit of heat to the equation but probably not enough to make any difference. However you are correct you can overshot the target temperature especially early in fermentation, eg the compressor turns off at 16*C and the cool air in the fridge keeps chilling, the over shoot will depend on a number of factors, is any heat being generated from the wort, thermal conductivity of your fermenter, volume of wort vs cooling capacity of the air inside the fridge. The over shoot, or under shoot of temperature is the biggest concern, especially if you are dropping the temperature of wort that started at say 24*C, best monitored for the first couple hours.

SCENARIO B
Probe Inserted in airspace.

Small fan to circulate air inside the fridge/freezer unit.
Set temp 17*C
Unit will turn the compressor on when the air temperature hits 19*C
Unit will turn the compressor off when the air temperature hits 16*C

The air temperature responds rapidly with a fan inside your unit (you can stand their and watch it drop), however just because the air temperature arrives at the target temperature does not mean your wort has. If you pitched a little warm, your fermenter could still be at the original temps, as I stated it does not take long for the air temperature to adjust. If the fermentation is producing heat, you will need to wait until the heat produced is sufficient to warm the air, to enable the compressor to turn on. The system will settle and move towards equilibrium, eventually. However it is early fermentation that plays a key role in fermentation flavour by-products.

In short Scenario A is better for early fermentation IMHO (people are free to sick there probes wherever they like). And Scenario B is better for long term lagering. After crash chilling I simply insert the probe for early fermentation and pull it up a bit and leave it in the airspace inside the fermenter (probably middle grounds between scenario a and B) for lagering.

In the early stages I want to know and measure the fermentation of my wort, not the air temps of my fridge which after awhile and all the action is over will reach equilibrium the wort.


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## Tony (26/2/07)

OK i thin ki know where PP is comming from here.

He is concerned with how the controller is going to crash chill the wort but then steady out to hold temperature when required.

most get confused with the whole concept of a thermostat and the temp controller controlling the fridge.

My set up has the probe in the wort, as u can see from the pics in the first page i think.

The probe is hooked up to a temperature controller that will control to within 0.1 deg c.

I have a 0-40 deg thermostat but it stays on 2 to 4 deg no mater what. It isnt the thermostat that is controlling the brews temp............ its the temp controller.

The trmp controller is hooked up to a power point that switches the power on and off the the fridge............ yes the fridges power lead plugs into my temperature controller.

If i put a 60 liter firmenter in with 50 literd of 30 deg c wory and want it at 20 deg to pitch, i set the fridges thermostat at 2 deg. this way the fridge will cool down to its coldest setting without freezing and cut out like its suposed to.

the temp controller will keep power on the fridge untill the beer is at 20 deg and them turn off the power when it reaches temp. the thermostat has cut in and out as it should to keep the fridge at its coolest temp to drop the wort temp quickly but hasnt run continuously and burnt it out.

it will them just cycle power every now and then to keep the wort at a steady say 19 deg. the fridge gets down to about 16 i think.

It works fine and doesnt over work anything.

Another thing is i have the end of my fridge thermostat in a 600ml bottle of metho to measure liquid temp and not air temp. It buffers it and snoothes out the fridges cycles

Its full of metho cause metho wont runt the metal and will never go mouldy. I just drilled a hole in the bottles lid and then sealed it with silicon

Its been like that for over 3 years

cheers

edit......... i was going to fix the spelling but there are some great ones in there so i left it 

cheers agian


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## browndog (26/2/07)

I'd like to stick my bib in here and for all the dummies (of which I am one) can tell you all the techinical discussion here is all about lag between your set point and actual temps. If the probe is in the fermenter and it says the temp at the center of the fermenter (or where ever the probe is) is at 18C then at the outer edges of the fermenter it is going to be colder when the controller tells the fridge to shut down. And the exact opposite for having the probe in the airspace. If you can imagine your ideal wort temp as a nice straight line then the actual temp will occillate above and below this in waves. We want our waves (and hence our lag) to be as shallow as possible. As the wort has a huge thermal mass compared to the airspace in the fridge, it will tend to occillate less giving a more stable temperature control IMHO. I'm no scientist, but have done quite a bit of proccess temperature control though my work. I happen to have a Data Logger with 12 inputs and am prepared to do an experiment to see how the temperatures work within the fridge and the wort. We should be able to sort this out and see exactly what goes on. I'd like to hear some ideas of where to place the thermocouples.

cheers

Browndog


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## PistolPatch (26/2/07)

Tony: I want your gear  My problem is that my fridge probe no longer works so I just have Frank's controller. Being a freezer, if I have the probe in the wort the freezer is going to run continuously and drop to at least minus 25 until the wort hits 18. Having it in the airspace inside the fermenter above the wort seemed to solve the crash chilling part really well which brings me to...

Browndog: You are the man. That'd be a great experiment. I'd be really interested to see how differently a probe taped to the side of the fermenter worked compared to it being in the airspace in the fermenter. I'm guessing that they would act similiarly but it would be great to know for sure. Look forward to hearing the results. 

I'm with you Warren on the lol's


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## kook (26/2/07)

browndog:

I'd try

- immersed in wort
- fermenter air/head space
- taped to side of fermenter
- immersed in water bottle beside fermenter
- hanging, loose in airspace of fridge

Would be interesting to see a graph of those temperatures over time, along with a log of when the compressor went on/off.


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## bindi (26/2/07)

kook said:


> browndog:
> 
> I'd try
> 
> ...



Oh yes please :super: I have done all the above and know what works here.
Simple, or is it? <_<


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## dean11 (26/2/07)

Personally I tape my temperature sensor to the side of the fermentor and insulate it with some foam. My view is because the fermentation process is exothermic and the fermentation rate is not constant i.e starts slowly speeds up then tapers off, I believe controlling the fridge air temperature could give rise to tempetature fluctuations far greater than what could occur by sensing the wort or fermentor side wall temperatures. 

But I agree with others that by doing this I will get temperature fluctuations of 2 or 3 degrees, but at least I know this is the extent of the fluctuations. By controlling the fridge air temperature you don't really know what temperature the wort may have reached unless you have monitored it.

This link provides some information on the subject of temperature control http://www.lemis.com/grog/Papers/freebeer/paper.pdf


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## jupiter (27/2/07)

ok, when i first set my controller / logger up i played around a little with the program (brewing a lager at 12degC saflager w34/70). i started off setting the temp according to the thermocouple taped to the side of the fermenter (red), then changed it to set the temp according to the fridge air temperature (purple) then changed it back as the fridge was cycling too much and i began to see the fermenter temperature rise. ambient is in blue (the sensor was on top of the fridge which is why it was kinda following the fridge cycle). each time you see the compressor cycle rate change, i made a change to the hysteresis points of the compressor. the fridge thermostat was completely bypassed and compressor is solely controlled by the logger / controller. it's rough as guts, but to do a proper analysis i'd need to put a thermocouple in the wort, but as stated in an earlier post that falls in the too hard basket and i'm happy with my thermocouple taped to the fermenter.





for those who care, each data-point was logged as an average of 600 1 second readings ie. 1 point every 10 minutes. data logger DT50


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## PistolPatch (27/2/07)

Browndog: Was just thinking that seeing you have so many thermocouples it would be very interesting to have any spares taped to the side of the fermenter at different heights. This should tell those who like to or are restricted to that method, the best height to put the probe at. Maybe same thing with the fridge temp probes.


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## marky_mark (27/2/07)

There are a lot of good arguments floating around with this thread. As for the motivation behind my method described earlier, I find that it gives me a good compromise between the accuracy of imersing the probe in the wort (or insulating it to the side of the fermenter) and avoiding temp. swings in the wort by putting it in the fridge airspace and controlling that temperature. 

It is simple, adds no extra sanitation concern, and compared to probes that I have placed on the side of the fermenter, completely insulated from the air, it provides an accurate wort temp reading, perhaps half a degree out. But, I'm willing to forgoe that level of accuracy for a greater level of control over temperature fluctuation, especially in lagers, where a few degrees of swing can produce unwanted esters or worse cause premature flocculation of the very tempremental yeast. 

Cheers,

Mark


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## browndog (27/2/07)

PistolPatch said:


> Browndog: Was just thinking that seeing you have so many thermocouples it would be very interesting to have any spares taped to the side of the fermenter at different heights. This should tell those who like to or are restricted to that method, the best height to put the probe at. Maybe same thing with the fridge temp probes.



To All,
No worries Guys, I have to organise the thermocouples and set this up, could take a couple of weeks, I'll keep everyone posted.

cheers

Browndog


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## PistolPatch (6/3/07)

Looking forward to it Browndog.

Also looks like Zizzle has done a bit in this area. Check out his Wiki article with graph called Temperature monitoring using a PC

I'm not too good on understanding these graphs (sorry Jupiter - haven't worked your one out as yet ) but it looks as though Zizzle is keeping his wort with half a degree and I know he uses Brissy's controllers.

I've also been posting here under the assumption that these controllers had a + or - 2 trigger (can't remember the correct word) whereas they are actually + or - 1 degree. Sorry about that.

Will PM Zizzle to see if he shed some light on where he shoves his probe


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## chimera (6/3/07)

> To All,
> No worries Guys, I have to organise the thermocouples and set this up, could take a couple of weeks, I'll keep everyone posted.



Browndog, PP etc. I know it's just a small point, but by thermocouple you really mean thermistors right?


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## jupiter (6/3/07)

Chimera said:


> Browndog, PP etc. I know it's just a small point, but by thermocouple you really mean thermistors right?


 i'm using k-type thermocouples cause thats what i had handy. t-type would be preferable.


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## chimera (6/3/07)

jup - yes, and no.

A thermocouple has a resolution of just over 0.04mV per degree C. If the analog input is designed to take a full scale TC input (around 60mV) then the ADC would have a resolution of about ~1.5 degrees for a 10bit ADC, ~0.4 degrees for a 12bit, ~0.1 for 14bit... 10bit chips are cheap, 12bit is a few dollars per chip in quantity and anything more than that becomes expensive - most applications opt for the cheapest they can get away with.

To 'find' extra resolution the system might then average successive readings within a threshold and look for step changes which will reset the averaging, hence the reason why you may see readings on a device which appear to have better resolution than they actually do. Systems with damping & step thresholds are also hard on feedback control loops and cause oscillations when the system isn't steady.

Bottom line: a feedback control system will never be able to control to better than +/- input resolution, and just looking at your graphs I reckon that might be +/-0.4 - so in reality it's doing pretty well.


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## browndog (6/3/07)

Chimera said:


> Browndog, PP etc. I know it's just a small point, but by thermocouple you really mean thermistors right?



K type thermocouples Chimera

cheers

Browndog


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## jupiter (7/3/07)

Chimera said:


> jup - yes, and no.
> 
> A thermocouple has a resolution of just over 0.04mV per degree C. If the analog input is designed to take a full scale TC input (around 60mV) then the ADC would have a resolution of about ~1.5 degrees for a 10bit ADC, ~0.4 degrees for a 12bit, ~0.1 for 14bit... 10bit chips are cheap, 12bit is a few dollars per chip in quantity and anything more than that becomes expensive - most applications opt for the cheapest they can get away with.
> 
> To 'find' extra resolution the system might then average successive readings within a threshold and look for step changes which will reset the averaging, hence the reason why you may see readings on a device which appear to have better resolution than they actually do. Systems with damping & step thresholds are also hard on feedback control loops and cause oscillations when the system isn't steady.



ah, a digitally minded person.

but i have to argue yes and yes, k-type thermocouples are reasonably linear over about 1500degC range but are only *accurate* to about +-1.5degC at the temperatures we want to measure (which is FA in terms of their full scale which makes them good for that range). T-types, although have a much smaller linear range, are much more *accurate* across the range we want to measure here.

http://www.microlink.co.uk/tctable.html

alot of logging/measurement equipment allows adjustment of the analog gain (setting the range) to the input of the ADC to increase *precision* of low-scale measurements. also, alot of cheap ADCs are logarithmic, so precision is much higher at lower ranges. number of bits and *resolution* is not the underlying factor in thermocouple *accuracy* here.

wide temperature range measurements, k-types are more suitable, for room temperature measurements go t-types (or just go platinum RTD)



Chimera said:


> Bottom line: a feedback control system will never be able to control to better than +/- input resolution, and just looking at your graphs I reckon that might be +/-0.4 - so in reality it's doing pretty well.


the switching on of the compressor was set at 12.5DegC, the 0.4 deg above the 12degC point had little to do the digital resolution of the loggers DAC but the actual set point i had programmed to switch the compressor on.

i been seaching around the house for the manual for the logger to look up the specs but can't find it. if anyone cares, it's a www.datalogger.com DT50. i can almost be sure that 1) the precision/resolution of the logger using a K-type thermocouple is a shit load better than +/-0.4DegC 2) the accuracy of the logger using a k-type thermocouple is crap (about +-3DegC).

edit: found the manual. the DT50 quotes a resolution of 0.01% over a temperature range of -250 to 1800DegC. it uses a programmable gain stage into a voltage-to-frequency converter feeding a 'Programmable time-base and frequency counter' to interface with the CPU for its ADC routine. all data is stored as 24bit (16 bit mantissa) floating point values.


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## Doogiechap (7/3/07)

Slightly OT but Jupiter do you know of any cheap WA sources for T Type Thermocouples ? I have a dual channel medical thermometer that uses T Type probes.
Cheers
Doug


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## chimera (7/3/07)

Looking at the programmable gains - 2uV resolution makes it a pretty capable data logger.

Hadn't even considered the inaccuracy of TCs, it's been a while since i've really thought about that. Most systems would have a manual correction factor but few people bother profiling TCs, and even if they did they would find they deteriorate with use. So long as it's repeatable you can tweak the process input and off you go.


Now - how to control your output to the compressor to improve the cooling control. What would it take to add variable compressor control to a fridge that was never designed to work that way?!


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## newguy (7/3/07)

Chimera said:


> Now - how to control your output to the compressor to improve the cooling control. What would it take to add variable compressor control to a fridge that was never designed to work that way?!



You can't. The closest you could get would be to make your own glycol jacket system. The fridge/freezer would be set to a temperature below the target temperature of the beer, and a custom controller would vary the system's pump which circulates the glycol. Refrigeration compressors don't take kindly to being rapidly cycled.


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## chimera (7/3/07)

It's probably not feasible for cost reasons I agree - but the concept is already a reality.

Commercial refrigeration has been doing it for years and domestic air conditioners are catching on with their inverter technology. Appliance manufacturers have already said that variable speed compressors will be the way of the future, which is sad considering I bought a new fridge last year!


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## newguy (7/3/07)

Chimera said:


> Commercial refrigeration has been doing it for years and domestic air conditioners are catching on with their inverter technology. Appliance manufacturers have already said that variable speed compressors will be the way of the future, which is sad considering I bought a new fridge last year!



Neat! Any idea how rapidly they're 'pulsed'? My only reservation concerns the switching transients that this new compressor design will kick back onto the mains.

Don't feel too bad about not jumping on the new technology bandwagon - the first generation of any new technology is always riddled with bugs. Besides, prices invariably fall over time as well.


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## chimera (7/3/07)

It's not pulsing, its changing the speed of the compressor which reduces the temperature drop through the refrigeration cycle.

If a compressor is a motor driven pump, the speed of an AC motor is a function of AC frequency. The 'inverter' in an air conditioner converts the AC power to DC, then either uses a DC driven compressor or converts back to AC again through a circuit where they can adjust the period of the cycle (depending on which patents the manufacturer holds)


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## therook (7/3/07)

hey fellas, shouldn't this be on a seperate thread, this has nothing to do with PP's original post

rook


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## jupiter (7/3/07)

Doogiechap said:


> Slightly OT but Jupiter do you know of any cheap WA sources for T Type Thermocouples ? I have a dual channel medical thermometer that uses T Type probes.
> Cheers
> Doug


i haven't looked recently, but i used to see extension wire cheap on ebay all the time so just make your own, it's a piece of cake.


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## PistolPatch (7/3/07)

therook said:


> hey fellas, shouldn't this be on a seperate thread, this has nothing to do with PP's original post
> 
> rook



Don't worry Rook, if I remember correctly, the thread got off-topic from the third post on  I'm sure though that all the technical gurus here, who speak a language I cannot comprehend, will solve not only the original question...

1. Where's the best place to put your probe for crash-chilling?

but also...

2. Where's the best place to put your probe for fermentation?

Once they have these answers, maybe we can put the results in the Wiki. That's worth waiting for!

Cheers Rook,
Pat


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## stm (23/1/09)

As I recently purchased a Fridgemate, I did a bit of a search on the forums for relevant discussions, and came across this interesting thread from a couple of years ago. Pretty much everyone agreed to disagree about the best place to stick your probe, so was wondering whether anyone had any further comments, have seen the light and changed their mind, have done further study and are now certain that theirs is the best solution, etc.

The options appeared to be:

1. In the wort
2. In the headspace in the fermenter
3. In the fridge (airspace)
4. In a bottle of water in the fridge (separate from the fermenter)
5. Taped to the side of the fermenter with electrical tape
6. Covered by a big blob of blutac (or foam/insulation and tape) stuck to the side

(Number 6 has appeared in some more recent threads as the option favoured by some.)

Interested to hear whether people have further thoughts; particularly the original commenters on this thread who have had a eureka moment since then.


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## wambesi (23/1/09)

stm said:


> 6. Covered by a big blob of blutac (or foam/insulation and tape) stuck to the side



I use diving suit material (old stubbie cooler/pencil case stuff) over the probe and taped onto the fermenter.
Works fine for my uses.


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## JonnyAnchovy (23/1/09)

wambesi said:


> I use diving suit material (old stubbie cooler/pencil case stuff) over the probe and taped onto the fermenter.
> Works fine for my uses.



Very good idea. At the moment I use cotton balls and gaffer tape. Seems to work, but not the best insulating properties, I'd imagine.....


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## wambesi (23/1/09)

JonnyAnchovy said:


> Very good idea. At the moment I use cotton balls and gaffer tape. Seems to work, but not the best insulating properties, I'd imagine.....



Can't claim it as mine though, saw people here using it.
Kids became minus a pencil case, sacrificed to a good cause.....


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## mikem108 (23/1/09)

I gaff tape it to the side of the fermenter halfway down with a layer of some sort of insulating material between the probe and the tape, like bubble wrap or polystyrene, then you are regulating the temp of the fridge based on the beer temp


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## matt white (23/1/09)

I use what they call plumbers tape. Its a silver, soft tape and sticks for months. The wort is consistently 2 degrees warmer than what my fridgemate says, going by the stick on 0-30 degrees thermometer.


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## np1962 (23/1/09)

I too tape to the outside of the fermentor with insulation covering. During active ferment and set to 18C the fridge can actually get down around 14C. 
If you think about it just sitting probe in fridge and keeping fridge at 18 your wort will probably be sitting up over the 22 degree mark. 
Taping to fermentor is the closest I can get to reading the true wort temp without actually sitting the probe in the wort and it is the temp of the fermenting wort that I want to control.

Nige


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## cubbie (23/1/09)

I would love to know if browndog carried out his experiment. I place my temp probe into a 1.5L bottle which seems to have a smaller following than the other methods. I account for the heat generated by the wort by adjusting the fridge temp to 2c below the ferm temp. Having read through the thread, I think the bottle does has some merit. Firstly it will prevent the compressor kicking in frequently (as may be the case measuring air temp) and secondly its thermal mass is greater than the air and less than my fermenter so it 

a. should cool down faster when the compressor is on yet stop before there is an overshoot in my fermenter
b. it should heat up faster than my fermenter and switch the compressor on before the fermenter gets an over shoot at the high end of the temp range

With this method I need to ensure that my fermenter when pitching is at the correct temp and when fermentation is over that I adjust the temp upwards (no heat production by fermentation.

I use this probe. Now if only it had a more accurate dial.

I plan to by a digital prob so that I can measure the temp ranges and difference of my beer throughout the fermentation cycle.

PS I like these old threads best, some great discussion.


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## np1962 (23/1/09)

cubbie said:


> its thermal mass is greater than the air and less than my fermenter so it
> 
> a. should cool down faster when the compressor is on yet stop before there is an overshoot in my fermenter
> b. it should heat up faster than my fermenter and switch the compressor on before at get an over shoot at the high end of the temp range




I see faults in both your arguments,

a. will fermentor actually get down to the required temp? or do you set controller to a lower than required temp?
b. would be correct if fermentation wasn't raising the temp of the wort, fermenting wort will heat up quicker than straight water.

Nige


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## cubbie (23/1/09)

NigeP62 said:


> I see faults in both your arguments,
> 
> a. will fermentor actually get down to the required temp? or do you set controller to a lower than required temp?
> b. would be correct if fermentation wasn't raising the temp of the wort, fermenting wort will heat up quicker than straight water.
> ...




a. I need to have cooled my wort to ferm temp before pitching, otherwise it may never to my ferm temp. having said that I do often pitch at around 24, though by the time the ferment kicks off it is down to 20c
b. I don't believe the fermentation is going to continually increase to temp of my wort. My estimate is that it adds about a constant 2c

Therefore if I want a ferment temp of 18c I cool my wort to 18c and then set the fridge to 16c. After fermentation has finished I adjust the fridge temp to 18c


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