Equipment & Workspaces PID display temp and other probes
@Slimfl08
Posted in Equipment & Workspaces
PID display temp and other probes
Hi all,
I recently purchased a new to me 2018 MCR-1. My first roasts on the machine I noticed a 30 degree difference from the BT and PID reading. When roasting my numbers were all over the place and I feel those batches were not executed right. I upgraded and recently swapped over the older 5mm thickness ET probe and BT probe to 3mm probes (have not swapped the PID) and I have noticed the PID temperature still has a variance of 30-50 degrees between the BT and ET. When the roaster is idle at room temperature readings are almost identical with the new probes while the PID seems off a few degrees. I know there is a lag with the PID since it's a thicker probe (5mm). I am wondering what is normal and should I even care what the PID is reading. I just ordered a new probe for the PID and will swap that out but in the meantime should I focus my charge temp to the PID reading or BT?
Hi @slimfl08
Stick to charging off of PID for now, and keep it consistent. Its normal for that number to be different than your BT and ET readings when the machine is heated and you are roasting. When it is cool, all your thermocouples are at room temp and should read similar.
Please keep in mind that when you swap out your PID thermocouple, the numbers on PID will be more responsive, but still read different than your BT and ET readings. This is normal. Calibrate to those new numbers once it is all installed.
Happy roasting!
Thanks for the response back! For the sake of my own learning curve and to add more to my knowledge of how the roaster is engineered is there a reason to charge off the PID vs the BT probe. I know RP labels the charge temp based on the BT probe and I have went under the assumption that if I charge at 405 then what RP is recording is what I should be using. Of note, my BT and ET are 30-40 degrees higher in temp compared to the PID.
We recommend charging off PID because BT rests lower in the faceplate and can fluctuate based on initial gas or fan settings. PID rests higher in the faceplate, and is less susceptible to the changes of gas and fan. Think of PID as, "real feel," in the roaster. This creates a more accurate starting point to charge, and once coffee is in the drum surrounding the BT probe, then we switch to that temp to steer the roast. It can also be helpful to record the PID temp in your profile name as a quick reference for yourself.
When you swap out your PID, that number is going to go higher and get closer to ET and BT. They will all still be different by 'x' degrees, but calibrate to those new numbers. You will assign meaning to those numbers when you are doing QC and cupping your coffee.
At the end of the day, consistency is key. Charging off PID will have you chasing your tail less as you are dialing in.
Awesome! Thanks for the thorough run down. I will be roasting soon and looking forward to the differences as my trials have been mixed! Have a good weekend and thanks again!
I added a screen shot of the latest roast. My PID temp was 415 and as you can see my BT was super high. Do you recommend leaving it as such? Or is it worth doing the sensor override for the BT? I would assume a sensor override on the BT would change all my numbers later down the line which may not be ideal.
You are correct. Sensor override will change numbers later down the line. Our recommendation is learn the numbers given, instead of offsetting to something familiar.
This profile looks like you have good control with this charge temperature. At the end of the day, how does the cup taste? If you are able to steer to desired results, that charge temp is working.
Happy roasting!
Thanks for the reply back. Overall, the cup taste, aroma/fragrance is good. But there is a less than desirable aftertaste I haven't been able to track down. It's almost like a dryness/sometimes astringency. I don't get it as much when I cup it, so I am leaning towards the brew method may be part of the issue.
@bryantscannell said:
Hi @slimfl08
Stick to charging off of PID for now, and keep it consistent. Its normal for that number to be different than your BT and ET readings when the machine is heated and you are roasting. When it is cool, all your thermocouples are at room temp and should read similar.
Please keep in mind that when you swap out your PID thermocouple, the numbers on PID will be more responsive, but still read different than your BT and ET readings. This is normal. Calibrate to those new numbers once it is all installed.
Happy roasting!
What's the expected lifetime for a probe? Is it worth keeping some in stock?
@raccroasters
That is an excellent question that I have yet to find one simple answer to. I have read that overtime thermocouples can get drift. I'll post the link to it below. As mentioned, I did swap over the BT and ET and have been pleased. I did though, recalibrate all of them. The newer ones really didn't need any adjustments. My OG drum probe did have a 7 degree variance. Regular calibration will probably remain on my radar as it's not too hard and in the grand scheme of things probably the reason all scientific calibrated devices get calibrated on a routine schedule.
I just roasted 6 batches of a Kenya AA last night and found the PID to not be helpful for charge if I wanted consistency. I got the best and most consistent roast when my BT/ET were as close to my reference roast. It’s been really frustrating using the PID now knowing that sometimes the BT/ET are so variable at the same PID and same gas/fan levels that it can shift the roast by even a minute.
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