Is this a probe or a controller problem?

[guypettigrew]

Ages ago I bought a second hand one of these to control a convector heater in the small shed I used to keep kegged beer in. It hasn't been used for some months.

It's now been pressed into service to control the temperature in a lovely new shiny 70 litre HLT with a 2.4kw element which I bought from the always helpful Paul at Angel Homebrew.

Trying it out today for the first time it has surprised me by needing to be set at 89C to maintain the temperature of the water in the HLT at 80C. This obviously isn't a real problem, and it maintains the temperature within a degree or so.

But why is it so off? Is it likely to be a problem with the probe or the controller itself?

Guy

[john luc]

Can it be recalibrated

[deanrpwaacs]

I had the same problem . If i recall you need to calibrate either the top end of the scale (hot) or bottom end (cold) .

[Rogermort]

I had the same problem . If i recall you need to calibrate either the top end of the scale (hot) or bottom end (cold) .

Me too. Which is why I'm about to switch to PIDs. At the moment I've marked my original controller with what temp it needs to be reading to be at, say 80c. Like the OP's it's way out.


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[orlando]

But why is it so off? Is it likely to be a problem with the probe or the controller itself?

Possibly neither. Could be that the probe is measuring a relatively cool spot, stirring the liquour before taking the temp should eliminate this if it is a problem. I recirculate my HLT liquour to ensure this doesn't happen. The larger the amount of sparge liquour the bigger the problem.

[donnyo]

I bought a second probe recently for my set up and first calibrated the digital thermometer at 0C with 60% crushed ice and 40% water to find it spot on so assumed it would be the most accurate. Then I checked my original probe with my PID which read 3 degrees too high and my new probe which was a few degrees less than that. Easy I thought so I set to calibrate my temperature controller by that amount and then turned on hlt elements to see if it was consistent as it heated up. Of course not ! Which made me realise that there really are design tolerances with each probe even if they have exactly same spec and to ask myself if my thermowell and probe truly accurately reflect temperature always! I put my thermowell away from the elements to avoid being influenced by them directly and to be honest now I use my Comark pen for the most sensitive mashing and I've learnt that at each of the key brewing stages each probe setup is inconsistently out just a bit. In the end I just left my PID as it was as it would be crazy for me to recalibrate for each probe and vessel at each of the temperatures in turn! I was fortunate that my Comark digital thermometer can be calibrated and aren't curate but even calibration is a funny thing as typical you calibrate at 0C. Regular hydrometer and glass thermometers are calibrated for 20C of course but i want HLT at 80, mash at 67, boil then flame out hops at 80 and ferment at 20 then 14 and then 4c.
I also did some forum reading and realise that a probe in a thermowell really needs to make a solid contact at the end of the thermowell to be most accurate so I have wrapped tape around the probe cable 4" from probe tip which sort of grips inside the well and allows me to jam the probe tight against end of well.
So what I've learnt is to that PIDS are brilliant at maintaining a given temperature and the probes and PIDS I use are good enough and my beer is just fine already. And with that I could roll over and get some sleep. But what if my fermentation temp is actually 19 not 20 and all these years my beer could be a bit better if only I had just 1 degree in one direction.
Imho it is a very useful exercise to compare all the probes and thermometer as a sanity check.

[AnthonyUK]

Not all probes are linear across wide temperature ranges
PT100s (used with PIDs) are significantly better than the NTC type (used with STC/ATC controllers) in this regard.

[guypettigrew]

Thanks all. Looking at the instructions it seems possible to calibrate the controller.

The instructions don't say how to calibrate it, just which parameter to access. Not very helpful! I might have a play later today.

Guy

[orlando]

I bought a second probe recently for my set up and first calibrated the digital thermometer at 0C with 60% crushed ice and 40% water to find it spot on so assumed it would be the most accurate. Then I checked my original probe with my PID which read 3 degrees too high and my new probe which was a few degrees less than that. Easy I thought so I set to calibrate my temperature controller by that amount and then turned on hlt elements to see if it was consistent as it heated up. Of course not ! Which made me realise that there really are design tolerances with each probe even if they have exactly same spec and to ask myself if my thermowell and probe truly accurately reflect temperature always! I put my thermowell away from the elements to avoid being influenced by them directly and to be honest now I use my Comark pen for the most sensitive mashing and I've learnt that at each of the key brewing stages each probe setup is inconsistently out just a bit. In the end I just left my PID as it was as it would be crazy for me to recalibrate for each probe and vessel at each of the temperatures in turn! I was fortunate that my Comark digital thermometer can be calibrated and aren't curate but even calibration is a funny thing as typical you calibrate at 0C. Regular hydrometer and glass thermometers are calibrated for 20C of course but i want HLT at 80, mash at 67, boil then flame out hops at 80 and ferment at 20 then 14 and then 4c.
I also did some forum reading and realise that a probe in a thermowell really needs to make a solid contact at the end of the thermowell to be most accurate so I have wrapped tape around the probe cable 4" from probe tip which sort of grips inside the well and allows me to jam the probe tight against end of well.
So what I've learnt is to that PIDS are brilliant at maintaining a given temperature and the probes and PIDS I use are good enough and my beer is just fine already. And with that I could roll over and get some sleep. But what if my fermentation temp is actually 19 not 20 and all these years my beer could be a bit better if only I had just 1 degree in one direction.
Imho it is a very useful exercise to compare all the probes and thermometer as a sanity check.

You found a 3 degree difference but the OP's is 9, I doubt very much this is a probe problem. I hope the OP does the experiment, a good whirlpool of the liquour with a mash paddle is all it will take to confirm one way or another.

[guypettigrew]

You found a 3 degree difference but the OP's is 9, I doubt very much this is a probe problem. I hope the OP does the experiment, a good whirlpool of the liquour with a mash paddle is all it will take to confirm one way or another.

Hi Orlando

Yes, done that. Forgot to mention it in my last post. Swirled it well after the controller had got it up to temperature kept it there for an hour or so.

Nice steady 80C measured using two thermometers, one glass, one digital. The controller showed 89C. Definitely worth having a go at calibration.

Guy

[orlando]

You found a 3 degree difference but the OP's is 9, I doubt very much this is a probe problem. I hope the OP does the experiment, a good whirlpool of the liquour with a mash paddle is all it will take to confirm one way or another.

Hi Orlando

Yes, done that. Forgot to mention it in my last post. Swirled it well after the controller had got it up to temperature kept it there for an hour or so.

Nice steady 80C measured using two thermometers, one glass, one digital. The controller showed 89C. Definitely worth having a go at calibration.

Guy

Yes, amazing!

[guypettigrew]

Sorted, the controller has now been calibrated.

Didn't really know what I was doing, but I got into the calibration bit of the controller OK. It showed 0.0, so I reset it to -9.0. Seemed a bit extreme, but worth a try.

The water in the HLT is now at 80C and being held there by the controller, which is now set at 80C. And the temperature read out on the controller is also showing 80C.

Job done!

Guy

[Jocky]

I had a similar issue with an STC-1000 with my HLT. Turned out that the probe was in a spot where the convection current meant that it was warmer than the rest of the pot.

I now give my HLT an occasional stir to avoid this.

[guypettigrew]

Tried stirring, same result. The calibration was definitely the issue.

Bit worrying it was so far out. Perhaps I should think about buying a new controller.

Guy

[Rogermort]

Sorted, the controller has now been calibrated.

Didn't really know what I was doing, but I got into the calibration bit of the controller OK. It showed 0.0, so I reset it to -9.0. Seemed a bit extreme, but worth a try.

The water in the HLT is now at 80C and being held there by the controller, which is now set at 80C. And the temperature read out on the controller is also showing 80C.

Job done!

Guy

Got exactly the same problem. Where did you find calibration instructions?


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