Thermometer Accuracy

[donburke]

I have brewed a few all grain batches recently that have all been thick and cloying, ummmm what have i done wrong ???

Mash temp was 66 degrees, or at least I thought it was

I thought I might have a dud thermometer, its a glass rod type with red liquid (allafrance brand) so i decided to do some testing

iced water read 1 degree, looks fine on the low end

boiling water read only 96 degrees ... umm there's the problem ... or so i thought

the thermometer has a link to a website help page labeled on it, so off i go ... click click

http://www.allafrance.com/content/technica...port-p-7-0.html

my thermometer is a TOTAL IMMERSION one, which means you must immerse the entire thermometer in the liquid up to the reading level

i stuck the whole thermometer in boiling water and got 100 exactly...

i had only been sticking the bottom part (maybe 1/3) into the mash water, which I guess gave me a reading approx 3 degrees lower than what the mash was, i.e. i was mashing at 69 not 66

just thought i'd post my experience to help others avoid making the same mistake

looking forward to making a more fermentable wort next brew ..

 

[MarkBastard]

Very interesting. I was using a similar one (I think, is yours a 'distilling' style one, about 25cm long and all glass with a red bulb at the bottom?).

I tried to measure mine. Stirring in ice water the coldest I was able to get it to was 1 degree or maybe a bit lower. Took a while to get a reading that low.

In boiling water I too was only able to make it read about 97 or so.

 

[big78sam]

It sounds suspiciously like mine. That explains why I get higher readings when putting the thermometer deeper into the mash. Interestingly enough there's only about half a degree difference with mine when I place it partially in the mash or completely in. There's no website details on mine though so it might be a different brand.

FWIW, I got mine from grain and grape. It was what they recommended for mashing. I was worried at the time this wouldn't be accurate enough but they assured me it would do the job...

 

[Cocko]

Wouldn't this apply to most thermometers?

View attachment Thermometer_Calibration_Instructions.pdf


Not being smart, just asking?

 

[donburke]

Very interesting. I was using a similar one (I think, is yours a 'distilling' style one, about 25cm long and all glass with a red bulb at the bottom?).

I tried to measure mine. Stirring in ice water the coldest I was able to get it to was 1 degree or maybe a bit lower. Took a while to get a reading that low.

In boiling water I too was only able to make it read about 97 or so.

yes, mine is 30cm long, like these http://www.allafrance.com/products/precisi...html#?width=158

 

[donburke]

It sounds suspiciously like mine. That explains why I get higher readings when putting the thermometer deeper into the mash. Interestingly enough there's only about half a degree difference with mine when I place it partially in the mash or completely in. There's no website details on mine though so it might be a different brand.

FWIW, I got mine from grain and grape. It was what they recommended for mashing. I was worried at the time this wouldn't be accurate enough but they assured me it would do the job...

there are different types, some are partial immersion, some total immersion, maybe your one is a partial immersion and thats why it only makes a little difference if you stick it all the way in ????

 

[donburke]

Wouldn't this apply to most thermometers?

View attachment 37460


Not being smart, just asking?

no, you cant adjust anything on a glass rod type thermometer, i was using it wrong

the point of this post was to explain that my thermometer is a perfectly working instrument, but i used it incorrectly

 

[Barley Belly]

yes, mine is 30cm long

 

[Barley Belly]

makes a little difference if you stick it all the way in ????

 

[donburke]

QUOTE (donburke @ Apr 22 2010, 07:04 AM) yes, mine is 30cm long[/quote]

but unfortunately very very thin :unsure:

 

[bcp]

I've been using a digital stick thermometer - it's just a matter of time before I drop it into the hot wort. Holding it over the hot wort waiting for it to read the temperature is not an elegant solution. I need a digital probe thermometer.

Anyone used either of these?

(No data on it, but at $2.93 including postage I'll probably get one to see anyway.)
http://offer.ebay.com.au/ws/eBayISAPI.dll?...&quantity=1

(It says 0.75% accuracy... % of what? Resolution 1c = ??? Does that mean it doesn't show decimals?)
http://cgi.ebay.com.au/Digital-LCD-Type-K-...=item45f257bbe9

Or does anyone have a digital probe thermometer on the cheaper end that they'd swear by? I'll pay more if I have to, but why do so if I don't need to.

 

[Fourstar]

I've been using a digital stick thermometer - it's just a matter of time before I drop it into the hot wort. Holding it over the hot wort waiting for it to read the temperature is not an elegant solution. I need a digital probe thermometer.

Haha, i always think that with mine. Hvant dropped her in there yet, although the display has some light fogging between the layers of plastic covering the LCD from splashes etc. :icon_cheers:

 

[coe-crl]

try the proscitech.com.au site. I got a hanna lab digital probe thermo from there for <$100 delivered. Thought that was pretty good given it's food grade and has reasonable tolerances and scale.

 

[pb unleaded]

I've been using a digital stick thermometer - it's just a matter of time before I drop it into the hot wort. Holding it over the hot wort...

Make a floating one using a lid of a coffee jar etc. with a hole and grommet in the middle.

 

[katzke]

Well you got me to test my glass stick. It reads right on in ice water and 10 degrees high or 216F in boiling water. I used an altitude adjusting chart and found my boiling point is closer to 206F.

Contacted the maker as I could not find the one I have on their site. Waiting for a reply. Now I need to see if I can find a calibration or compensation chart. I also need to find a known good thermometer to test it at mash temp. After all that is the temperature we are concerned about and why I got the glass stick in the first place. My original dial thermometer was ok in ice water and close at boiling but way off at mash temperature. To make things worse it was not reliably off.

 

[absinthe]

I've been using a digital stick thermometer - it's just a matter of time before I drop it into the hot wort. Holding it over the hot wort waiting for it to read the temperature is not an elegant solution. I need a digital probe thermometer.

Anyone used either of these?

(No data on it, but at $2.93 including postage I'll probably get one to see anyway.)
http://offer.ebay.com.au/ws/eBayISAPI.dll?...&quantity=1

(It says 0.75% accuracy... % of what? Resolution 1c = ??? Does that mean it doesn't show decimals?)
http://cgi.ebay.com.au/Digital-LCD-Type-K-...=item45f257bbe9

Or does anyone have a digital probe thermometer on the cheaper end that they'd swear by? I'll pay more if I have to, but why do so if I don't need to.

you want a RTD type probe not a K type. the K type are +-1C and the RTD depending on the unit its used with are+-0.1C