Need everyones help on a PID problem

[Wildcat]

Thanks for the replies.

WCK.  What you said makes perfect sense. I think. :D  For me, a fairly constant low and slow provides excellent results for my taste buds.  I have the OBS.

Giz.  I have been looking at some of the stuff that Thermoworks sell even before anything was posted here.  Will probably invest a little after our trip and several birthdays.

Arcs.  I need to learn a little more before I can understand how to experiment with the "I".  Electronics is new to me.

[Arcs_n_Sparks]

Arcs.  I need to learn a little more before I can understand how to experiment with the "I".  Electronics is new to me.

I understand the frustration in finding "ground truth." Almost sounds like the Heisenberg problem: the act of measuring something changes what you were trying to understand. The only time I wind up three thermometers (PID included) is for sausage, since I don't want to render out.

[West Coast Kansan]

Two drinks behind and catching up fast now.  Took a break for ice cream. Hard to be troubled when eating icecream. Been a long day but got the loin out and vac packed. it looks great. Another week ahead  :)

[Wildcat]

I readjusted the Pb on the PID twice yesterday afternoon to match the Maverick.  If I had left it alone it would be 13 degrees difference between the two.  After the meat temp reached about 150 the box temp (PID and Maverick) continued to be the same all night.  This is about the same as it did last time.  I guess either the Maverick gets a little weird during the first part of the smoke/cook or the PID needs a little tweaking.  Don't know how to adjust the "I".  Probably will need to get another "clock" to figure out which one is acting up.

[Mr Walleye]

Wildcat

I find that there is a larger difference between the ET73 and the PID when I first put a load in. Then once the load starts to reach alittle higher temp the difference seems to become less. What I have done is adjust the offset once the load has been in for a few hours (3 or 4 hours with a butt). By setting it up this way I just ignore the difference and once the meat starts to get up to temp it balances out. I'll just mention though that my probes are not in the same location in the cabinet. In my situation it seems the meat effects the ET73 a little more than the PID temp probe. This makes sense because my PID TC is in the back of the cabinet and I usually clip my ET73 close to the meat to see what the meat is experiencing.

Mike

[Wildcat]

Thanks Mike.  Both probes are next to each other on mine.  I think I might order the MicroTherm 2.  Here is the link: http://www.thermoworks.com/products/handheld/microtherma2.html

I think I will be able to nail down whether the problem is the Maverick or the calibration of the PID once I can determine what the true temperature is.

I liked the Thermopen accuracy that Iceman recommended but the 7 does not have a high enough range.  The 3 does but is not near as accurate.  The Microtherm 2 has more flexability and better accuracy to boot for just a few bucks more.

[Mr Walleye]

Looks like a nice unit Wildcat.

I should be receiving my MTC & THS-113-181 probe shortly but I don't have it yet. I like how small the probe is on this especially for sausage and with a 3 second response time it seems pretty impresive. Here is a link to it.
http://www.thermoworks.com/products/handheld/mtc.html

Mike

[Wildcat]

I looked at that as well.  Can't argue with the price.  Accuracy not as good but I guess a couple of degrees is close enough.  I am still thinking it over.

[pensrock]

Wildcat,
   You keep mentioning that you are adjusting the 'Pb' setting in your PID controller to get it to read the same as your Mav. I have never used an Auber controller but most controllers have an 'offset' setting which you can use to make the controller read the same as another device. Every controller I have ever used the 'Pb' setting is for the proportional band which is part of the tuning to control the output of the instrument. In other words when you run an autotune the controller will set the proportional–integral–derivative settings for you, not saying you may not need to tweak a little here and there. But I get the impression you are adjusting the 'Pb' in an attempt to match your Mav instead of using the 'offset' function. I may be wrong because I have not used that instrument but maybe someone who has one will be able to explain this better.
   Just a thought.... one other thing, most digital controllers can be set back to factory calibrations by changing the thermocouple type, leaving the set up mode, then changing it back, but it may change other settings in the controller so go through all the setups and write them down before doing something like this unless you really know what you are doing.
   One other thing to consider is the calibration tolerances of the equipment you are using. I think you are using a type K thermocouple it is most likely +-5 degrees F, unless you have a 'special limits' thermocouple which is +-2 degrees F. I really doubt is yours is special limits. Your controller is also most likely +-5 degrees F. The extention wire between the controller and thermocouple will also have some effect. This is only your PID set up, the Mav will have its own tolerances.
Just my two cents worth, I do not know if it will help any but its something to consider.
pensrock

[Mr Walleye]

I just checked the Auber manual and here are a couple of descriptions from it.

Measurement Accuracy - .2% Full Scale or +/- .2 degrees C Thermocouple Input with Internal Automatic Compensation.

Pb = Input Offset.


I'm not sure about the accuracy of the exact TC that Wildcat is using. I'm not even sure of the accuracy of the Omega TC that I'm using. Interesting comments though Pensrock. At a .2% accuracy does this equal .4 degrees at 200 degrees F?

Mike

[Wildcat]

Here is something a little different.  I was smoking 2 butts and when the first one was done, I took it out and repositioned the remaining one and I also moved the Maverick box temp probe and the PID back to the same location.  After the box temp recovered there was an 8 degree difference in the two and remained that way for the remaining 4 hours.  Maverick reading lower.  I did not change the Pb settings this time after the move.  Could this problem be as simple as a problem with the Maverick probe wire?  On the other smokes after the temp got to 140 - 150 the readings remained the same with each other, but they were never disturbed.

[Mr Walleye]

That's a good question Wildcat. It would be interesting to have another thermometer and TC to check it against.

Mike

[Arcs_n_Sparks]

Wildcat,

Are you using an insulated TC?

[Wildcat]

Not sure.  It is the 383 from Thermoworks.  I have only used it 2 or 3 times now.  The Maverick is kind of old and I got it used.

[Wildcat]

Yep, here is a link to it:  http://www.thermoworks.com/products/probe/tc_wire.html