Jumpy PID PV on e-brew set up with RTD?

[itinerantbrewer]

been e-brewing now for a couple years (thanks Jkarp). for a while now (9 months?) my thermo probe to PID connection has been very jumpy.

got this stuff from Auberins. It is an RTD via a QD to the good SS wrapped cable to a panel mount QD, which on the inside then goes to the PID. at first it was rock solid. then somehow after a year my over-sized SSR (I brew 1-2 times a month with 120v 4gal batches and got the 40amp SSR and companion heat sink) melted down. I replaced it with new version of same ssr. didn't notice any other problems at first but then noticed that my PID PV reading would jump around every time I bumped the SS cable. I inspected everything and couldn't find any problems. so I replaced all the temp probe cable run and panel mount QD (again via auberins) I still have the problem though it is not as pronounced--the cable can take a bit more jostling. Auberins didn't have a lot to say on what the problem may be.

Anyone else have this problem with a PID and RTD temp probe?

I guess I could replace the temp probe itself, but not sure how that would have gotten messed up (I disassembled the temp probe pieces and all looked well). Also the PID. But say I do this, for $120, how do I avoid this in problem in the future?

 

[itinerantbrewer]

Fail



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[floormatg]

Are you using the FILT function in the setup on your PID? Though it won't fix the problem, it should mask it by slowing the response time on your temp. display... It's made to smooth out the temperature readings. Set it to 5 and see what happens.

 

[itinerantbrewer]

Thanks floormatg. I don't think that's the problem. when you plug it in and set it up, you can tell it jumps around (including back and forth between 88 and -88 for example) when you are moving the cable around. I jingle the cable a bit to 'calibrate' it with a standalone digital thermometer. when they line up (after a brief amount of messing with it), I gently set the cable down and it is fine from there. Not that big a deal, but again, for the pimped out version wrapped in SS braid, I expected more. I understand they work well for others.

wondering if anyone has had this problem and discovered their PID was actually at fault/fried.

 

[floormatg]

I would be leaning towards the qd at the rtd end then.... You've pretty much replaced everything else, and it looks like a poor connection...

Do you have a multimeter? You can try disconnecting the panel end of the cable and measuring the resistance across the terminals while you move the cable around...

 

[itinerantbrewer]

Ok thanks. That makes sense. That part is cheaper than a PID. And probably easier than finding my multimeter, if I even have it here.

I'm not sure how those auberins thermowells work. I'd think they'd be pretty solid. I took it apart to look for issues but didn't see anything


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[rossi46]

I have had to re solder both of my ss wrapped cables, just take those little tiny screws out and disassemble the qd ends to expose the wires.

 

[augiedoggy]

behind those ss shielded $6 rtd cables hide very thin wires...if it isnt whats been mentioned above I had the same issue and after replacing mine once already because the developed a short at the end of the sensor under the spring I recently decided to upgrade to these which are waaay better and easier to unplug to clean my kettles...

http://www.ebay.com/itm/380938165742?_trksid=p2059210.m2749.l2649&ssPageName=STRK:MEBIDX:IT

 

[ajdelange]

... noticed that my PID PV reading would jump around every time I bumped the SS cable.

Anyone else have this problem with a PID and RTD temp probe?

Yes, all the time. Your controller measures the resistance of a loop containing the RTD. A fraction of an ohm change can impose an error of a couple of degrees. Thus poor/erratic contact, dirt... anything like that can induce error. I use the traditional temperature sensor flat plugs/sockets for interconnection and find that I have to unplug, clean the blades and replug fairly frequently to get stable temperature readings. These things get vapor condensing on them, wort splashed on them etc. Little wonder they 'gum up' from time to time.