thermocouple/multimeter lost accuracy, wtf?

[drummer4gc]

hey everyone,

i've done some reading around and it sounds like there are some people out there who use a thermocouple and multimeter for their temperature readings. I know it is not the most accurate method, but it was working well for me until this past weekend. I was really stoked to hit my mash temperature dead on for my first AG batch, until i realized that my thermocouple was reading 222F for the boil. Currently, the beer is fermenting at 60F according to the fermometer on the side of the bucket, but my multimeter is telling me 70F. It appears to be reading 10 degrees hotter all the time.


This thing used to be accurate! any idea what happened? i'm trying to decide if i want to try another thermocouple (the one i have is pretty beat up, but the adaptors to fit normal thermocouples into multimeters are as expensive as a new cheap multimeter), or if i should invest in a better temperature monitoring system.

if there is some way to get my probe measuring correctly again, i'd love to hear about it.

 

[drummer4gc]

another thought - has anyone used this ebay meter?

TM-902C K Type Digital Thermometer + Thermocouple Probe | eBay


that's about as cheap as it gets, so i wouldn't expect much longevity...but if it's reasonably accurate, i could buy two of them.

 

[passedpawn]

If you buy the cheapest thing on ebay, from China, you're likely to continue having these problems.

You never mentioned what your DMM is, so it's hard to comment on that.

Thermocouple junctions are very reliable. Probably your meter is giving you the problem. However, any short in the thermocouple wiring will cause wild inaccuracies. I'd get another TC first, since they can be gotten dirt cheap.

 

[drummer4gc]

its an ideal 61-310 DMM. only problem is it needs an adapter to fit a normal, replacement thermocouple, and the adapter costs $20. id rather put that $20 towards a more reliable meter if my meter is the problem...i just dont know how to figure out if its the meter or the thermocouple wire.

 

[passedpawn]

its an ideal 61-310 DMM. only problem is it needs an adapter to fit a normal, replacement thermocouple, and the adapter costs $20. id rather put that $20 towards a more reliable meter if my meter is the problem...i just dont know how to figure out if its the meter or the thermocouple wire.

Not really easy to determine where the problem is with a tc. Thermistors and RTD are easy because they are resistive devices. Just pay some $.

 

[Fat_Bastard]

The batteries in your meter might be getting low.some multimeters get twitchy with weak batteries.usually in the form of lack of repeatability.