PID temp controller question

[SanPancho]

so we wound up with some weird temp probes on some fermenters. Like these

However, theres isn't a nice plug on the housing or other connection point. Kinda funky looking. But If you open it up theres three wires running down into the probe, for rtd (i assume), so pretty sure we need PID type temp controller.

As im looking at the pid selection theres rtd/thermocouple/universal/etc inputs, but when it comes to outputs theres either relay, analog, alarm, or ssr/ssc.

We’re using basic solenoids. Probably 24vac. Or maybe dc.

Which type of pid output do we want? My wild ass guess is Relay.

 

[doug293cz]

Measure the resistance between all three possible pairs of leads. If two pairs read ~100 ohms, and the third pair reads 0, then you have PT100 RTD's. If you get 50 ohms instead of 100, then you have Cu50 RTD's. If you get anything else, then IDK (but post results here, and maybe we can figure it out.)

Those junction box's for making connections are pretty common in industrial equipment. They are made for use with the wiring in conduit (either flexible or rigid.)

Relay outputs will work for solenoids, but remember you must provide the source of power to the relays/solenoids. If you have two alarm relays on the PID you can probably set up one to close on high limit and the other to close on low limit (which can be a few degrees apart.) You then can do cooling and heating with hysteresis.

Brew on

 

[augiedoggy]

those are actually what most of the professional rtds look like in a lab environment..
I may be wrong but I believe some use these modules inside I assume for wireless communication. I havent read much on it honestly..
https://www.ebay.com/itm/4-20MA-50-...821689?hash=item2cae3d6af9:g:ibkAAOSw3YNXZ7jr

heres more like yours,
https://www.ebay.com/itm/Temperatur...470296&hash=item59327fd346:g:xB0AAOSw3QldUL2j

 

[Vale71]

Industrial grade RTDs aren't usually connected directly with the electronics as that can easily be 10-50 meters distant and the signal would degrade to the point of being unusable. 99% of the time they use (wired) transducers that give you a current between 4 and 20 milliamperes within a given temperature range regardless of how long the connection is. They are a bit more complicated to connect as they would need to be powered (that's what the third wire would be for) and you also need to define the temperature range that you want them to measure. With most of them this is done with jumpers or microswitches on the transducer.
I suggest the OP open one unit up and look at what's inside and eventually post a picture.

 

[augiedoggy]

your other option here is to just pull the rtds and swap them for thermisters you can use with regular temp controllers... the rtd should pull out of the the thermowells you have now.. would be a lot more cost effective than pids for conical temp control..