Thermometer Issues

[BNVince]

I have two digital thermometers from two different companies. One is made by Taylor and the other by Maverick. Yesterday I was doing my second AG batch and I used one thermometer to measure the strike water and the other to measure the temperature in my MLT after I doughed in. I was off by 7 degrees!

I rectified the situation but after the batch was done I ran a little test. I poured some hot water out of the tap in to a glass and put both thermometers in the water. As I suspected, one was reading 7 degrees lower than the other one.

7 degrees isn't slightly off in the beer brewing world and I don't want this messing up my mashes. Of course, I'm not sure which thermometer is the accurate one or if either of them are accurate.

So I was thinking, boiling water can only reach 212 degrees at sea-level. Could I figure out which one of these things is off by using boiling water as a bench mark?

 

[david_42]

Yes. An even better test for homebrewers is some cheap vodka. It will start boiling off the alcohol at 172F.

 

[BNVince]

Boil some vodka? Hmmm...that sounds interesting.

 

[Bobby_M]

You can test them at both 212 by boiling and at 32F by using icewater. Neither are the useful temp but you'll get an idea of which one is closest to being correct.

 

[BNVince]

Well I tested them both with boiling water. The one read 210 degrees and the other went above 212 which just makes the thermometer read HI.

I'm going to assume that the one reading 210 is getting the closest reading to what is actually correct. Therefore, I'll have to subtract 7 degrees from what my other thermometer says to get an accurate temperature.

Side rant here but what the hell? How can digital thermometers be off by so much. We can put a man on the moon but...

 

[The Pol]

I had the Taylor therm with the wire lead to the temp probe. If that probe gets wet, if it is not sealed, when moisture gets inside it ruins the probe. It will read slightly off and then finally just read "HI". Sometimes you can dry it out by placing the probe in an oven at 350 for a while, but eventually they just fail. Look into something like this.

http://i168.photobucket.com/albums/u189/PolTavern/BREWING/Insidetherm.jpg

http://i168.photobucket.com/albums/u189/PolTavern/BREWING/Therm.jpg

http://i168.photobucket.com/albums/u189/PolTavern/BREWING/DSCN0111.jpg

 

[njnear76]

Well I tested them both with boiling water. The one read 210 degrees and the other went above 212 which just makes the thermometer read HI.

I'm going to assume that the one reading 210 is getting the closest reading to what is actually correct. Therefore, I'll have to subtract 7 degrees from what my other thermometer says to get an accurate temperature.

Side rant here but what the hell? How can digital thermometers be off by so much. We can put a man on the moon but...

Which one was off? The one by Taylor or the Maverick?

 

[abracadabra]

Here's another problem with digital themometer and testing at 212*F or 172*F.

My digital themometer is only 2*F off at 175*F but 6*F off at 150*F.

I think the best method is to get a calibration themometer.

I got a calibration themometer from my LHBS for around $6-8 then tested the digital and marked the differences in indicated reading vs actual temp. both on the digital themometer and in a reference book.

 

[Warped04]

You can test them at both 212 by boiling and at 32F by using icewater. Neither are the useful temp but you'll get an idea of which one is closest to being correct.

Spot on Bobby. It's how we were "required" to calibrate our thermometers. Crushed ice works best for the Ice water.

 

[BNVince]

Which one was off? The one by Taylor or the Maverick?

The maverick I believe. But now I don't know which end is up and which end is down.

 

[BNVince]

I just did the icewater bath test. The Taylor read 33 and the Maverick read 39. I'm going to say that the Maverick is off by about 6 to 7 degrees higher than the actual temperature.

 

[Bobby_M]

Man, 7 off is the difference between a dry beer and a completely sticky sugar water. Good thing you found out now.

 

[AnOldUR]

Man, 7 off is the difference between a dry beer and a completely sticky sugar water. Good thing you found out now.

Old thread, but my wife came home last night with a Maverick thermometer (cheap from a going out of business sale.) Testing shows that it's off by 2.5 degrees, so I went to their website to see if they will replace it. Here's what they say:

FAQ
I tested my thermometer in boiling water and it reads 208ºF instead of the expected 212ºF. Is there anyway to calibrate my digital thermometer?

No. All of our digital thermometers have a tolerance of +/- (3-4) degrees F.

The probe has a silicone wire, so I thought it might be good for the mash, but it is not sealed where the wire meets the probe and they say to not submerge it even when washing. Between the inaccuracy and lack of waterproofing I would recommend staying away from these thermometers.





Edit:
The machinist in me says that the quote above states that all of their thermometers will be somewhere between 3 and 4 degrees off, either on the high side or the low side.

 

[Special Hops]

Just because it's digital does not mean it's more accurate then an analog thermometer.

 

[dstar26t]

Item #46610-024 is about as accurate as you're going to get for the money with a water proof probe thermometer. My old BB&B Pyrex reads 2 degrees low (at mash temp) which explains why my previous beers weren't attenuating like they should have.