Immersion Thermometer Help

[bignath]

Howdy brewers,

spent the day going over the brew rig tidying some things up and giving it all a good clean out. Decided to check the calibration of my large faced dial thermometers on my mash tun and my HLT.

I have a long stem, glass, total immersion thermometer made by "alla france". It is one the bio temp ones where the liquid inside is safe if it ever goes bang over foods/beverages as it breaks down to water and carbon dioxide or something like that....

My question is, i was wondering if anyone has used a thermometer like this and are they accurate? Against this thermometer, my two mashmaster dial thermo's were a couple of degrees out (which i suspected due to a recent thread i started about high attenuation and low gravity readings).

According to the website (www.allafrance.com) they seem to make some pretty fancy thermo's so i'm hoping that mine is a good one, and that it's accurate, and then by turn of events, i've hopefully solved my problem i posted about a few weeks ago....

hope someone can offer an opinion on these thermometers.

*pic below is of a 76mm depth marked immersion thermometer - mine is identical to this but is total immersion.



Nath

 

[Kai]

Those thermometers, maybe, most likely have a 73.14% chance of perhaps being correct. Or perhaps not.

Unless you paid an awful lot of money for them and received a fancy certificate to go with them, they might well be out by a few degrees. Or might not.

I worked in a wine laboratory once, one night shift I decided to compare all the spirit thermometers to one another. They were an argumentative bunch and stank like hell when broken.

Mashmaster thermometers, I bought two a few years ago and both were out, but they have a calibration screw if I recall correctly.

The most important thing, I think, is just having a thermometer you can rely on to give consistent readings every time. That is, one you can in theory rub out those potentially inaccurate degrees celsius and replace them with units of "i want my beer to finish drier... not so dry... thicker... thickerrrrrrr"

My current mash thermometer is a cheap little milk frothing thermometer. I couldn't resist buying it as it has 65-70C listed as the 'optimum frothing zone' on the dial.

 

[bignath]

Those thermometers, maybe, most likely have a 73.14% chance of perhaps being correct. Or perhaps not.

Cheeky bugger!

Thanks for your response Kai. Yeah my mashmasters have the calibration screw on the back, i just turned it until all three matched the temp in the glass of water i was using (big glass).

I was operating under the suspicion that a $25 stem immersion / candy style thermometer from a HBS should be pretty bloody accurate. Even though i paid a lot more than that for each of my mashmasters... I can't help but think that a chemical (mercury or other chemical) would be more sensitive than a mechanical dial. Happy to corrected though, and if i've got it the wrong way around, i did note the discrepancy between the two mashmasters and the stem thermo, so i can put the settings back at a later date if needed.

 

[avaneyk]

I recently checked my digital thermometer by measuring the temp of a pot of boiling water. It was out by 1 % which is within the precision range given by the manufacturer. I'd suggest setting your dial themos up the same way. Just remember that water boils at different temps for different altitudes above sea level

 

[katzke]

My experience with dial thermometers is they can be on in ice water, close at boiling and way off at mash temps. Or they have a correction curve that is unpredictable.

My glass stick is also off, however it has a straight line correction that is well within the way it is marked.

I will never trust a dial thermometer for brewing no mater how much it costs and how many adjusting screws they put on the back.

 

[MHB]

I stock the same thermometer, they are very good value for money, without spending ridiculous dollars they should serve you well. Of the many dozens sold we have yet to find one that was more than ^oC out, when checked against the shops reference NATA certified thermometer I can live with that.

The big issue I have with dial thermometers isn't so much accuracy as hysteresis, there can be quite a lot of error in the period between temperature rising and falling.

MHB

 

[Kai]

Cheeky bugger!

Thanks for your response Kai. Yeah my mashmasters have the calibration screw on the back, i just turned it until all three matched the temp in the glass of water i was using (big glass).

I was operating under the suspicion that a $25 stem immersion / candy style thermometer from a HBS should be pretty bloody accurate. Even though i paid a lot more than that for each of my mashmasters... I can't help but think that a chemical (mercury or other chemical) would be more sensitive than a mechanical dial. Happy to corrected though, and if i've got it the wrong way around, i did note the discrepancy between the two mashmasters and the stem thermo, so i can put the settings back at a later date if needed.

A certified stick thermometer runs a few hundred dollars, from memory.

I think any error in these units isn't so much the liquid contained therein (mercury or alcohol) but maybe the manufacturing of the glass surrounding the liquid (ie the size of the capillary tube and bulbs)?

And I also remembered, a big potential source of error on these is if any separation of the liquid within the column occurs through (mis)use. It pays to check that regularly if you use them a lot.

 

[katzke]

I also found out they should be storred standing up and not laying down. Not sure why or where I found this bit of information. I think it was a makers site.

It is also important to make sure if you have a line to have it stuck in to the line. That is where they are designed to be used. A full imersion needs to be dunked all the way not just dipped in.