BCS Coefficient Calculator

Suggestions, Problems, Availability, etc. Everything is up for discussion.
Post Reply
gimbo
Posts: 3
Joined: Wed Aug 26, 2015 3:35 am
Bot?: No

BCS Coefficient Calculator

Post by gimbo » Wed Mar 30, 2016 10:23 am

I apologize, I’ve read the various posts on how to use this utility, but I just can’t figure it out. I was wondering if someone could write up some instructions in laymen terms on how to go about making all my probes read the same temp.

User avatar
bbrally
Posts: 200
Joined: Sat Mar 27, 2010 3:59 am
Bot?: No
Location: Vancouver, BC or NST, Thailand
Contact:

Re: BCS Coefficient Calculator

Post by bbrally » Wed Mar 30, 2016 6:17 pm

The instructions are lacking. I'll try and write something up over the next couple of days when I have some free time. If you have any specific questions, feel free to ask.
Move, copy, clear processes/states: http://manipulator.from-ca.com/
Perform coefficient mods: http://calculator.from-ca.com/
HMI Builder: http://bbrally.altervista.org/GUI/index.html
HMI Builder latest ver: http://bbrally.altervista.org/guibeta/index.html

User avatar
oakbarn
Posts: 803
Joined: Thu Jan 05, 2012 2:28 pm
Bot?: No
Location: Texas
Contact:

Re: BCS Coefficient Calculator

Post by oakbarn » Thu Mar 31, 2016 4:27 pm

I have been playing with the Calibration tool and I get some "strange reading", or so it seems.

I used the Sampling Calculator:

I had a 600 ml beaker with 4 Probes and a Thermapen.

I did an Ice Water Bath for the 32 Degrees F test. My Thermapen read 32.0 F

I then repeated the test with 104 Degrees F and 158 Degrees F Water that was also being stirred with a stir plate.

All Probes and the Thremapen were in the bath at the same time and left to settle. On the 104 and 158 I added Hot Water to 106 and 160 and let it cool with the probes in the bath.

I locked the valuves based on the Thermapen at 32, 104.1 and 158.0.

Here are my Temps:
alltemps.png
alltemps.png (55.28 KiB) Viewed 1580 times
And Here is the Calibration.
158_2.png
158_2.png (183.69 KiB) Viewed 1580 times
The resistence at 32 seems varied and the coefficents do not look close to me.

Also Probe 2 coefficents are negative. (Scroll Right)
Since I did not "trust" the variation, I did not save it to my BCS.

Any comments?

User avatar
oakbarn
Posts: 803
Joined: Thu Jan 05, 2012 2:28 pm
Bot?: No
Location: Texas
Contact:

Re: BCS Coefficient Calculator

Post by oakbarn » Thu Mar 31, 2016 5:23 pm

I goT brave and updated all but the negative coefficents and ran the test again.

Probe 2 is the one not "calibrated". and updated.

I was correct in that it was not quite right.

Temps on Second Try:
alltemps-2.png
alltemps-2.png (55.56 KiB) Viewed 1576 times
Calibration Second time. Some of the Resisitence looked better but it would NOT let me save it. I reverted to the defaults. Not broken, don't fix it!
try2.png
try2.png (28.78 KiB) Viewed 1576 times

User avatar
bbrally
Posts: 200
Joined: Sat Mar 27, 2010 3:59 am
Bot?: No
Location: Vancouver, BC or NST, Thailand
Contact:

Re: BCS Coefficient Calculator

Post by bbrally » Thu Mar 31, 2016 8:17 pm

Oakbarn, on your first post, something was wrong with your probe2 resistance reading at 32F. You should be getting readings about the 25K - 30K range. The 51K reading you were getting is why the coefficients are not working out, it's just to far outside the range.

Here's a sampling that I just completed. The temp at 105 was actual temp of the bath, but I changed the value up and down 1 degree to show the difference only a degree off one reading will make to the coefficients.
104 deg.jpg
104 deg.jpg (95.44 KiB) Viewed 1569 times
105 deg.jpg
105 deg.jpg (95.14 KiB) Viewed 1569 times
106 deg.jpg
106 deg.jpg (95.33 KiB) Viewed 1569 times
The BCS sensitivity to resistance measurement is very course. At 212F the step change is about 60 ohms, at 32F the step change is about 600 ohms. To see what a difference that makes to the coefficients, enter the BCS default coefficients in the 'coefficient calculator' tab and then vary the resistance of only one of the values by that step change and see the difference it makes in the coefficients. A change of only one or two 'steps' can be all it takes to bring the coefficients into negative territory. Also vary the temperature by a degree, to see what an inaccurate temperature will do to the coefficients.

I think I need to post a big caveat notice to the sampling calculator tab, about the fact that due to the low resolution of the resistance measurement, poor results may be encountered.

I'm not sure why it wouldn't let you save the values the second time. The 'save' button will be enabled if the values of the selected probes are valid. Since your 'save' button isn't greyed out, it should have allowed a save.
Move, copy, clear processes/states: http://manipulator.from-ca.com/
Perform coefficient mods: http://calculator.from-ca.com/
HMI Builder: http://bbrally.altervista.org/GUI/index.html
HMI Builder latest ver: http://bbrally.altervista.org/guibeta/index.html

gimbo
Posts: 3
Joined: Wed Aug 26, 2015 3:35 am
Bot?: No

Re: BCS Coefficient Calculator

Post by gimbo » Wed Feb 01, 2017 5:51 am

bbrally,

Wondering if you were ever able to update the calculator instructions?

Thanks

User avatar
bbrally
Posts: 200
Joined: Sat Mar 27, 2010 3:59 am
Bot?: No
Location: Vancouver, BC or NST, Thailand
Contact:

Re: BCS Coefficient Calculator

Post by bbrally » Wed Feb 01, 2017 5:58 am

I never did, but oakbarn has written an excellent help/tutorial on its use.

I'm not sure where he's posted it, if he even has. Perhaps he'll respond.
Move, copy, clear processes/states: http://manipulator.from-ca.com/
Perform coefficient mods: http://calculator.from-ca.com/
HMI Builder: http://bbrally.altervista.org/GUI/index.html
HMI Builder latest ver: http://bbrally.altervista.org/guibeta/index.html

Post Reply

Who is online

Users browsing this forum: No registered users and 2 guests