Temp probe calibration question

[Dland]

I've noticed that the temp probe for my Auber EZ boil does not seem to read true consistently though temp spectrum. I know how to adjust it's reading in the EZ boil. I calibrated at a known for sure temp, 212F, boiling, and analog thermometer on kettle agreed.

But when I then set mash water temp to around 165, even with stirring, with same temp probe, I am getting a lower reading on the Auber than on the analog, and the analog one is right, also tested w hand held digital thermometer. Was trusting Auber reading, ended up with a cooler than target mash. Are these things just not that accurate, or is there an optimal temp to calibrate to, or some other trick?

 

[mabrungard]

You really need to compare the reading of your PID temp sensor to an accurate thermometer in water that is somewhere in the mashing temp range. I've got a NIST certified lab thermometer that I use to check the accuracy of my working thermometers and sensors. I've found that my electronic Thermoworks (Thermapen maker) thermometers are easily within a degree of the lab reference. I use the less expensive Thermoworks thermometers since the Thermapen is drastically overpriced.

 

[swimIan]

Make sure you are mixing the water either by stirring or pumping too.

 

[postalbunny]

Those RTD probes can read 1-2deg hot or cold, but usually always read the exact same temp. You'll want to calibrate in a known temp rage... usually with a known good therm. Those auberin pids usually have a "Pb" setting where you can account for the offset the probe is off. They can be up to a couple degree's off, but they'll be the same amount "off" for the entire temp range.

 

[BitterSweetBrews]

I was just getting ready to post a similar question. Over the years I have used numerous PT100 probes on my equipment and have always calibrated them to boiling, using 211F at my altitude. I find that no two sensors are ever the same. I have had to compensate anywhere from 1-10 degrees, + or -. I then label each probe for this offset to key into my PID.

I have used numerous types of thermometers to compare temps during mashing. I have an analog, round faced brewing thermometer on my mash tun. I have used many different temp probes to compare and calibrate it. I have used many BBQ probes, quick reading thermometers and PT-100 or K type thermocouples to double check temps, many times simultaneously. But I still wonder how much any of these readings can be trusted for accuracy. They never seem to be the same.

I am re-thinking my process.

As Martin has said and I am coming to agreement on we need to calibrate our probes at mash temps with a very accurate source or at least a few sources that read the same.

The criticality of Mash temps is more important then where boiling is.

I do wonder why temps show different, on different probes. The readings of like probes should be the same. The probe mechanics should be identical and the temperature reactions within them should be the same.

Tim Trabold
BJCP pending ranking
SOB (South Omaha Brewers)