STC1000 Temp Probe Placement

[mtb]

Since getting serious with fermentation temps, and buying a fridge to dial into a specific temperature and thus control my fermentation temp with OCD-like accuracy, I've wondered how close to the wort my STC-1000's temperature sensor needs to be in order to get the most accurate reading without going to unnecessary lengths.

Initially I had it simply taped to the interior side of my fridge.
Later I realised this wasn't measuring the temp of the fermenter itself, nor the wort, so I attached it to the exterior of my fermenter with some tissue laid over it in order to insulate and measure only the fermenter temp, not the fridge's ambient air temp.
Tonight, while pondering fermentation temps for my first rendition of the Adequate Saison, I wondered if I'd get a different reading by submerging the probe in the wort itself. off I went to sanitise and dunk said probe, and its readout is 0.2deg higher than the reading from the exterior placement w/ insulation.

The purpose of this topic is twofold;
a) to inform all the less experienced brewers here that an STC-1000 costs bugger all (eBay it) and is awesome, and
b ) to discuss whether there is any merit to placing the temp probe in the wort as opposed to attaching to the exterior of the fermenter.

What are your experiences?

EDIT: despite living in the MSN Messenger era, typing b ) without the space in between still catches me out with the good ol' sunnies smiley. b)

 

[MartinOC]

For the sake of 0.2C, it's both simpler & safer (ie. less risk of introducing infection) to just tape it to the outside of your fermenter.

RDWHAHB.

 

[AJS2154]

Hi mate. I use a doubled over piece of bubble wrap, about 120mm square with the probe underneath it. I tape it on with packing tape. Never had it fall off, in fact it is hard to get off the stainless, and it is safe and easy.

I would never take the chance of infecting the wort when the probe works well enough (+/- 0.2 degrees according to your research!!).

Anthony

 

[Beamer]

Hey mtb, I have my prob sit directly above the fermentor (chest freezer set up), then after the beer was in the freezer for two days ill took it out for a reading and measured the temp. The beer is 1.9 degrees lower then the freezer temp, so I just set the temp 1.9 higher than required.

Cheers,
Beamer

 

[TwoCrows]

Masking tape and a stubby cooler works well taped over the probe on the outside of the fermenter. Brewing at the temp you want within 1 degree is close enough to perfect.

 

[Autopilot80]

Get a cheap thermowell from ebay. If you are using a plastic fermenter they are super easy to install.

 

[mtb]

Agreed gents, not worth the infection risk for 0.2deg. Might butcher a stubby cooler and get out the duct tape! Autopilot I did consider a thermowell but with six fermenters in rotation it's a PITA.
Good advice from all, cheers

 

[camelbak28]

Just an idea, but Mash master has the Ntc probes for about $30 (includes the sensor and a thermowell). I bought one ages ago and drilled a 10mm hole in the lid top of a 1ltr bottle of water and inserted the probe down into it. I place this bottle next to my fermenter in the fridge and within hours the temp has pretty much equalized between the fermenter temp and the bottle with the probe in it.

 

[mtb]

My only concerns with that are a) higher thermal mass of the fermemter and b ) higher temps being created by the fermentation activity. A separate bottle of water won't heat up like an active fermenter

 

[dr K]

There is a basic flaw in the logic (ha ha) here, for whilst the STC1000 resolution is 0.1C the accuracy is at best +- 1C.
You are certainly correct about the thermal mass and the exothermic nature of fermentation, some people just tape the probe, others tape and insulate.
Fermentation works over a range, keeping the temp fairly constant (whilst in the range) is more important than the actual temperature.

K

 

[manticle]

I have measured the temp of fermenting wort on several occasions, have an average of the difference bewteen fermenting wort and ambient temp, set my fridge to accommodate. For example - for 18 deg ferment, I set the stc at about 15.5 - 16.

 

[Mr B]

I use a peice of elastic around the fermenter, which holds a peice of foam with the probe under it. No tape etc to stuff around with.

By elastic I mean black ~7 odd mm dia stuff from a chandlery.

 

[kaiserben]

I'm currently testing a dual-probe Raspberry Pi controller that I've built, which has data logging, so I have graphs of what is happening to temperatures.

I have one probe dangling in the air of my fridge. The other controller is taped to the side of a plastic fermenter and insulated from the air with a cut off bit of a stubby holder. I'm considering whether to put a probe into the wort to get an even better idea of what is happening.

But anyway here are some graphs from my first series of testing:

1. Bringing a Helles (previously at diacetyl rest temp) down for a quick period of lagering.



X axis is time (in hours)
Y axis is temp (in C)
Grey lines are what I'd set the target temperature to.
Blue is the sensor measuring fridge air temp.
Green is the sensor taped to the fermenter.

2. Set at 1C. (note the scale on the X axis has changed to Days.Hours:Minutes)



3. I then changed temp to 2.3C (and added a x2 zoom feature to the graph)

 

[Old_Lonely]

Hi guys, I used tape on the first brew with the stc and it took forever to get the stain for the tape off. Now I use a good size piece of Blue-Tack. No problem with stains and you can use it over and over. Cheers

 

[Coalminer]

My probe (S/S Craftbrewer probe) sits in the wort and reads directly

I have no issues with sanitizing a probe.
After the infection risks from multi-step starters, flasks and stir plates, no-chill worts and glad wrapped fermenters
and all other equipment that needs to be sanitized the same process should be used with your probe
It just hangs in there and glad wrap over the lot.

Probably should be more worried about the nice moist warm environment of a fridge kept at 18C and all the nooks and crannies in there to harbour moulds and bugs

 

[MHB]

I'm currently testing a dual-probe Raspberry Pi controller that I've built, which has data logging, so I have graphs of what is happening to temperatures.

I have one probe dangling in the air of my fridge. The other controller is taped to the side of a plastic fermenter and insulated from the air with a cut off bit of a stubby holder. I'm considering whether to put a probe into the wort to get an even better idea of what is happening.

But anyway here are some graphs from my first series of testing:

1. Bringing a Helles (previously at diacetyl rest temp) down for a quick period of lagering.

Test 3.jpg

X axis is time (in hours)
Y axis is temp (in C)
Grey lines are what I'd set the target temperature to.
Blue is the sensor measuring fridge air temp.
Green is the sensor taped to the fermenter.

2. Set at 1C. (note the scale on the X axis has changed to Days.Hours:Minutes)

Test_5b stopped at 1 day and 11 hours.jpg

3. I then changed temp to 2.3C (and added a x2 zoom feature to the graph)

Test 7.jpg

I've been extoling the virtues of putting a small fan in brewing fridges for a couple of years.
It looks like you have the right setup to evaluate the idea properly, If you get the opportunity I would love to see the data logged results of what happens if you do.
Just putting 25L of water at say 25oC and cooling it to 1oC, One run with the fan on and one with the fan off and logging the rate of cooling would be great.
I just use a computer fan from Jaycar and the plug on lead they sell.
Mark

 

[kaiserben]

I have been planning to add a fan. I'll definitely get around to it eventually.

 

[TheWiggman]

These threads pop up often enough and we argue about the differences between taping, where to control it, does the side of the fermenter really work etc. etc. Has anyone just checked the difference between the two on the same vessel?
If you have a submersed thermowell like I do, then you can. I got mine from Beer Belly, pictured below -

I also have a small bit of foam wrapped around the fermenter, which insulates the probe to the side. One day I pulled it off the side, then stuck it in the thermowell.

0.3°C difference.

I use the thermowell lid when I have 1 brew going and/or when doing lagers because it's tidier. For a second brew I just stick it to the side because it's essentially no different. As MartinOC said RDW...

 

[Danscraftbeer]

I installed a thermowell into the side of my kegmenter about mid depth. I used to just have the temp probe on midway inside the fridge. I'm quite sure there is a big difference. The fridge works much harder to counter the rise in temp when ales are in full ferment. Meaning previously the brews could have been getting as much as to ~3 to 4c higher than the stc1000 was reading.

 

[kaiserben]

Because I know you all love graphs ... here's an ale. I suspect most ales will look almost exactly like this.



Green is the sensor insulated and taped to side of fermenter (and the one dictating when the fridge switches on or off. Blue is just a sensor dangling in the air inside the fridge).

Basically it shows from the point I put the fermenter into the fridge when it was roughly 21C.

It took me 3 hours to get from 21C down to 17C (my pitching temp).

About 40 minutes later I pitched my yeast, then left it to do its thing. It has held 17C +/- 0.2C very steadily. (graph finishes after approx 2 days 5 hours, when I did a quick wifi firmware update and reboot of the system. Have since started a new graphg and it's continuing exactly as it left off).

EDIT: Inserted explanation of the colours on the graph.

 

[tumi2]

Mate, love the graphs. What app do you run on the raspberry pi. Im currently looking at craftbeerpi for the app. Im now trying to work out how to best connect my heat belt to the Solid State Relay so i can auto set my temp probe via the app.

 

[kaiserben]

The actual software has been written by my Dad, based on me telling him what I want it to be capable of. It's still a work in progress at this stage.

 

[sp0rk]

Mate, love the graphs. What app do you run on the raspberry pi. Im currently looking at craftbeerpi for the app. Im now trying to work out how to best connect my heat belt to the Solid State Relay so i can auto set my temp probe via the app.

Keep in mind that CraftBeerPi doesn't currently support fermentation control (I believe)
Pretty sure Manuel has said somewhere that he's looking at adding it some time down the track
Currently CraftBeerPi just controls AG brew rigs

 

[kevinj]

[SIZE=11pt]Hi Kaiserben[/SIZE]
Love the graphs

Question, which probe controlled the fridge?

To me they show what I have thought, that comparing the oscillation of the wort temp to be within the oscillation of the ambient temp.
Due to the thermal mass of the wort.
Their for, you only need to control the ambient air and the wort will slowly follow behind.
If you put the the fridge controlled probe on or in the wort, by the time the wort hits the lower or upper limits, the lag time of the fridge to reverse the change would be greater, causing the oscillation of the wort temp to be greater.

Or am I dreaming because its to early to be drinking.

 

[kaiserben]

I've got the probe that's on the wort (and insulated from the air) controlling the fridge. (the green one).

In my settings I can make either probe do the controlling. In earlier brews I had tried it with the air temp sensor (blue) controlling the fridge, but quickly realised that if I wanted to chill down to yeast pitching temp, or crash chill etc, that, with the air temp swinging wildly by comparison and quickly passing my target temperature and the fridge turning off too often, the wort took too long reach target temps.

It would slowly follow behind, but far too slowly for me. I get far more control using the on-wort probe.

I've also got a delay setting that prevents the fridge cycling on/off too often (from memory it's same as BrewPi's setting of 5 mins after being on and 8 minutes after being off). In practice it's this setting that controls the oscillation of the actual wort temp.

The oscillation of the on-wort temp probe is barely +/-0.2C.

EDIT: After seeing how temperatures behave in a few different ferments, the blue probe is merely a curiosity and not really required anymore.

 

[Hopasauraus]

what are the settings you use on the controller?