Howto: Calibrate Temperature Probes

Describe your system and processes, and post your config file.
JonW
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Re: Howto: Calibrate Temperature Probes

Post by JonW »

Check out this thread: http://forum.embeddedcc.com/viewtopic.p ... 623&p=9186

There is a link to a good web based tool in the first post.

http://www.thinksrs.com/downloads/progr ... ulator.htm
mdunlop
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Re: Howto: Calibrate Temperature Probes

Post by mdunlop »

I'm lost, fustrated, and starting to regret this BCS. I have spent hours trying to calibrate my probes. Please help.

I've read the instructions and came up with the three coefficients. When I plug them in, my temperature read out show zero. So, taking a step back and trying to understand the coefficient calculator, I pluged in the default data provided on this thread and the coefficient for A does not equal the stated value.

The thread stated at Temp 0c = 29481 ohms, 40c = 5595 ohms, 70c = 1991 ohms ( I converted the temps to C because the calculator asks for C)

When I put these numbers into the calculator I get
A= 1.028179684e-03 (this is not the stated value)
B= 2.392402336e-04
C= 1.565756581e-07


My valules for one of my probes: 40.4F (4.66C) = 24937.9 ohms, 78.7F (25.94C) = 9415.6oshm, 93.8F (34.33C)= 6619 ohms

Plugging this into the calculator I get
A=1.732732146e-03
B=2.324561088e-04
C=1.093093991e-07

I plugged this exactly into the the system inputs an outputs and when I hit apply the numbers change to
A=.0017327
B=.0002324
C=1.092e-7
Why they changed I have no idea but I'm obviously not cut out for this.
brewstarke
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Re: Howto: Calibrate Temperature Probes

Post by brewstarke »

Your default coefficients will depend on the probe you use. Are they the probes that came with the BCS from Brewers Hardware? I believe the newer probes have changed from that original post. That info should be somewhere in the forums.
As far as your discrepancy with the values they look OK to me in that one is just using what I'd call scientific notation. The e-03 at the end of your string of numbers is just telling you that they've moved the decimal over 3 places to the right from the original. I believe the BCS displays it that way on you so when you hit save they are just bumping over the decimals on you. Although your C coeff seems to be rounding down the last place in the decimal which seems off...

Have you tried upgrading to 4.0?? I'd recommend it. To me it's a huge improvement in everything from the look down to the ease of making edits. And the recipe utility is super sweet. AND for your issue there's a super easy temp calibration utility that makes calibrations as easy as pie...

Good luck!
mdunlop
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Re: Howto: Calibrate Temperature Probes

Post by mdunlop »

brewstarke wrote:Your default coefficients will depend on the probe you use. Are they the probes that came with the BCS from Brewers Hardware? I believe the newer probes have changed from that original post. That info should be somewhere in the forums.
As far as your discrepancy with the values they look OK to me in that one is just using what I'd call scientific notation. The e-03 at the end of your string of numbers is just telling you that they've moved the decimal over 3 places to the right from the original. I believe the BCS displays it that way on you so when you hit save they are just bumping over the decimals on you. Although your C coeff seems to be rounding down the last place in the decimal which seems off...

Have you tried upgrading to 4.0?? I'd recommend it. To me it's a huge improvement in everything from the look down to the ease of making edits. And the recipe utility is super sweet. AND for your issue there's a super easy temp calibration utility that makes calibrations as easy as pie...

Good luck!
Im still runnig 3.7.1. Last night i was going through the Wiki trying to learn as much as possible. When I followed the direction for firm ware updates all I saw availble to download was 3.7.1

Im using probes bought from Brewshardware. My understanding was every probe will have a slightly different resistance. My take was if I purchase 4 of their probes I needed to collect the resistance reading at three different tempertures for all 4 and load those reading into the calculator to get new coefficents for each. Is that not correct? Am i suposed to use a standard coefficent provided by the manufacture of all Probes? This dosn't seem correct because the probes were off while comparing them to a digital thermometer that I was using during the calibration experiment

Thanks for the explination on the A value. So, from an imput perspective do I move the decimal over the proper place and input into the bcs?
A=1.732732146e-3 or A=.001732732146
B= 2.324561088e-4 or B= .0002324561088
C= 1.565756581e-7 or c= .000000156575681

I entered by using ...e-3 ,...e-4,...e-7. Maybe my format for input is the issue or my incompetence.
mdunlop
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Re: Howto: Calibrate Temperature Probes

Post by mdunlop »

I think i just answered my own question on format. It doesnt matter.

Using the default coefficients in the BCS everything works but im not sure on its accuracy. When i enter just my A value and leave the default B &C values my probe temp reads zero. If I load my calculated B&C values and leave the default A everything work but again not sure on the accuracy piece.

My head hurts!

I guess i need clarity on using defaults values on the Brewersharewar probes or am i on the right track with calibrating each probe which would generate different A,B,&C numberes for all four of my probes.
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Re: Howto: Calibrate Temperature Probes

Post by JonW »

mdunlop wrote:I guess i need clarity on using defaults values on the Brewersharewar probes or am i on the right track with calibrating each probe which would generate different A,B,&C numberes for all four of my probes.
I've always used the default values with the BH probes. The default values are standard/average values provided by the manufacturer, but since they are resistance based, you sometimes get one that is off a bit and may need calibration. It's not a bad exercise to calibrate them just to see if they are different.
TrickyDick
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Re: Howto: Calibrate Temperature Probes

Post by TrickyDick »

brewstarke wrote:Have you tried upgrading to 4.0?? I'd recommend it. To me it's a huge improvement in everything from the look down to the ease of making edits. And the recipe utility is super sweet. AND for your issue there's a super easy temp calibration utility that makes calibrations as easy as pie...
Where does one access this utility? I cannot seem to find it, only a PID tuner utility, under the settings > BCS Utilities link

Is there a particular web browser that is recommended for using with BCS by the way?

TD
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Re: Howto: Calibrate Temperature Probes

Post by brahn »

The temp calibration utility was actually written by bbrally on this forum, and it's available at http://bbrally.from-ca.com/

For web browsers, I do the development on Chrome and my brewdays are pretty much exclusively run from my phone using Safari. I do at least some testing on Firefox and Safari on the desktop as well. The safest bet is Chrome, but if you find an issue with another modern browser please post something so we can fix it.
TrickyDick
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Re: Howto: Calibrate Temperature Probes

Post by TrickyDick »

Hello,

I am preparing my new Ebrew system for use and will be doing a general cleaning and rinsing of all components and during that time, I hope to test the accuracy of the BCS displayed temp of each probe vs reading of a Thermapen thermometer.
I live in FL, and getting water temp below 72 degrees is impossible without using ice. I read the suggested calibration temps are 0,40,70 C. Since I'll need to heat the entire volume of the kettle filled with water bath enough to submerge the probe, is there a "best practice" way to calibrate?

I guess what I am asking is, if I fill my HLT and set the BCS to recirculate the water bath at a particular temp, I already know its going to be off a few degrees. Assuming the temp is uniform throughout the bath when I take a temp at the top with the thermapen for calibration temps, are the temps at which I obtain these reading very important (ie: 0,40,70) and does it matter how full the HLT is with water as long as the thermocouple is submerged (because a large ice bath would need a LOT of ice in a 20 gal kettle).

Thanks!

TD
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Re: Howto: Calibrate Temperature Probes

Post by bbrally »

It doesn't matter the temps at which you take the readings, as long as they are accurate and reasonably spread out. One could argue the only really important temp is one at which you require accuracy (ie. mash temps). I've calibrated mine at 0, 65 and 100 celsius as 0 and 100 are very easy to acquire accurately and 65 is right around mash temp where I care most.

As for a method, I would take the probes out of your kettles and place them in a smaller pot on the stove. No need to heat/cool gallons of water for this. Just let the temps/resistances stabilize for a few moments while you take the readings, and confirm the probe is only touching the water, not resting on any part of the metal container.
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