PID temp freaking out. Bad cable?

[Cameronl]

While brewing last weekend, my Inkbird PID for the HLT started freaking out, with the temp readout jumping up to 600F, back down to 120F, then showing the display for no probe attached (orAL).
Helpful video:

My initial thought is that it is simply a bad cable. But is there anything else that could cause this problem. Do temp probes go bad?

 

[HighVoltageMan!]

Cables can go bad. Assuming the temp probe is a RTD.

The PID is an ohm meter and the RTD is a temperature variable resister. Based on the resistance, the PID can determine the temperature. Any small changes in the circuit (the PID, the wire, the connectors and the RTD) will change the temperature output. Even the smallest changes in the circuit will drastically change the reading.

1. Visually check the wiring. Look for anything loose, sharp bends in the wire (indicates a break), corrosion or discolored pins in the connector, dirt or grime in the connector.
2. Inspect the RTD. Look for any physical damage to the connector or the probe itself. These probes are pretty hardy unless they get physically abused.
3. Hooked it up. Note the temperature and start to gently bend the the cable near the connectors, look for any change in temperature. Even a few degrees indicates a fault or problem. Typically this is the problem. If not, move on to the RTD connector and do the same.
4. If you have an ohm meter, measure the resistance in the RTD, you should see the resistance change as you hand warms it up, it should move in resistance fairly slowly.
5. Start shot gunning! Spares are awesome for this. Swap out cable first, then probe. Spares are what most homebrewers lack, so a little trouble shooting will have to do.

I had the same problem a few months back, but it was a little harder to detect. My mash temp read 10 degrees high, after some trouble shooting on the fly and during a brew I found a connector with a little corrosion on it.

Good Luck!

 

[Cameronl]

Cables can go bad. Assuming the temp probe is a RTD.

The PID is an ohm meter and the RTD is a temperature variable resister. Based on the resistance, the PID can determine the temperature. Any small changes in the circuit (the PID, the wire, the connectors and the RTD) will change the temperature output. Even the smallest changes in the circuit will drastically change the reading.

1. Visually check the wiring. Look for anything loose, sharp bends in the wire (indicates a break), corrosion or discolored pins in the connector, dirt or grime in the connector.
2. Inspect the RTD. Look for any physical damage to the connector or the probe itself. These probes are pretty hardy unless they get physically abused.
3. Hooked it up. Note the temperature and start to gently bend the the cable near the connectors, look for any change in temperature. Even a few degrees indicates a fault or problem. Typically this is the problem. If not, move on to the RTD connector and do the same.
4. If you have an ohm meter, measure the resistance in the RTD, you should see the resistance change as you hand warms it up, it should move in resistance fairly slowly.
5. Start shot gunning! Spares are awesome for this. Swap out cable first, then probe. Spares are what most homebrewers lack, so a little trouble shooting will have to do.

I had the same problem a few months back, but it was a little harder to detect. My mash temp read 10 degrees high, after some trouble shooting on the fly and during a brew I found a connector with a little corrosion on it.

Good Luck!

User name checks out.

Thanks, HVM! This is very helpful. Will tinker this weekend.

 

[Broken Crow]

User name checks out.

Thanks, HVM! This is very helpful. Will tinker this weekend.

While you're at it, I highly recommend Caig Deoxit for cleaning all your signal connections;
https://caig.com/deoxit-d-series/

 

[Cameronl]

While you're at it, I highly recommend Caig Deoxit for cleaning all your signal connections;
https://caig.com/deoxit-d-series/

Deoxit is great stuff. I use it for restoring vintage radios.

So I finally had some time to work on this. pulled out the Deoxit... and it cleared it right up! The connector on the cable at the probe end was a little gunked up. A couple of squirts and all is well.