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Old 05-17-2012, 06:35 PM   #1
lcat45
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Default Help/Advise on PID problem

I have been trying on and off to resolve a PID/thermocouple (J type) problem since I've had this system was put together....the problem is the PID has never read the correct temperature and I've tried two thermocouples from 2 different suppliers and know one at least works....have worked very closely with Auber Instruments and their support is really good, but the thermo didn't work on my system even though after sending it back they ran a test and found it to be in working order, so that leaves the PID also from them and it appears to also work correctly.......they at one point suggested it was an inductance problem and that is certainly a possibility but I don't even know how to test that any further than reroute it as I've done with no difference.....I have enclosed 2 pics of my system to show the setup....the pid is behind the small tank as the hot wort comes out of the tank and goes to the MT where it is recirculated....the other pic show the back of the thermo to show that it does come up through an electrical enclosure that also has everything else crammed into it to get it to the panel.....I have even removed it from the routing under the table and just ran it over the top of everything to see if that made a difference, but zilch, nada had made a difference....anyone have any ideas to try next....the only thing I'm trying to do is manage the temp of single or multi step mashes....thanks, Lee


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Old 05-17-2012, 06:45 PM   #2
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Lose the terminal lugs, the dissimilar metals will throw the readings off, just land the wire directly to the PID controller. With thermocouples the wire is two different metals, joined at the junction, any splices of other types wire will screw the readings up


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Old 05-17-2012, 09:03 PM   #3
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Thanks kladue for the reply.....don't question your judgement but that's the way it came from the mfg and I would think it would be different if that was a requirement......don't mind doing it as it's not working anyway, so nothing ventured nothing gained I guess....thanks
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Old 05-18-2012, 01:52 AM   #4
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Is the indicated temp off a couple degrees, or off by about 30 degrees or more.
Most of the controllers offer an offset value you can use to correct for small temperature differences < 20 degrees, display difference values that are more than that amount is usually caused by a wrong thermocouple selection in the controller, or wrong thermocouple type installed.
Another thing to check is the wire colors on the thermocouple, white /red is a type J, yellow red is a type K which seems to be more readily offered. If you were sold a type J, it should be white/red, not yellow/red type K.
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Old 05-18-2012, 02:12 AM   #5
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Thanks again for the reply.....yes it is red/white and I cut off the connectors and used bare wire and it didn't make any difference.....I tried to calibrate and put it in water with a lot of ice...had to put in an offset of -10 to get it to go down to 32 but when I placed it in some hot water the temp on the unit changed but was about 30 less than the water temp should have been....I"ve even gone through all the options of changing the type from all the values in the book that it should work with and none of them work either as I was thinking it was sent as a different type than ordered.....I'm at the point now of starting to look at other options as I wanted to add a lot more automation in valves and temp monitoring so if I didn't need to make some beer soon I'd just give up on it and start heading in another direction to go with some other ways of doing the same and more...any other ideas appreciated or any other alternatives also open for consideration.....many thanks again

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Old 05-18-2012, 03:41 AM   #6
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The PID unit sounds suspect as there is supposed to be a cold junction reference circuit built in?, which if working correctly should have made the offset a couple degrees at most near freezing and it should have tracked across the span. Alternative approach would be to use a 100 ohm RTD sensor instead of the thermocouple as this just uses an internal amplifier circuit, not a cold junction chip.
You get what you pay for with the budget controllers, some essential things are less than perfect which give you the problems you are having when using thermocouples.
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Old 05-18-2012, 01:34 PM   #7
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Actually I did try one from Auber Instruments and it never worked for me either....I sent it back and they tested it and said it did work so I'm of the opinion that the PID itself doesn't work properly at this point but I kept thinking that maybe it was an inductance problem and nothing else but that apparently isn't the case.....think I'll just start a new thread and ask for suggestion on doing a new system from people who have experience with systems that do work and one that is current and can be expanded to do what I may want to do in the future...any input appreciated....regards
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Old 05-18-2012, 02:56 PM   #8
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I assume you've configured the PID to the proper type of sensor/sender, right?

I had made the mistake of simply hooking up a sensor to a 2nd-hand PID, and it wasn't configured for the K-Type sensor I was using. Turned it off, picked the right configuration on the PID, and it immediately read correctly.

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Old 05-18-2012, 03:05 PM   #9
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Yeah Canuck, I have actually tried every one that the PID supports and none work with the J type that I have.....I'll probably send it back to the supplier and see if it's bad or if they can figure out what's wrong....bout over working with pids and this whole setup.....need a system that works...not into troubleshooting forever...would be nice to be able to make a brew once in a while....thanks
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Old 05-18-2012, 03:34 PM   #10
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Quote:
Originally Posted by lcat45 View Post
Yeah Canuck, I have actually tried every one that the PID supports and none work with the J type that I have.....I'll probably send it back to the supplier and see if it's bad or if they can figure out what's wrong....bout over working with pids and this whole setup.....need a system that works...not into troubleshooting forever...would be nice to be able to make a brew once in a while....thanks
I've found K types to be a bit more common. I've been using K's from Auber.

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