2 JLD612 thermocouples cause error

[McRoth]

I just built a controller using 2 JLD612 PID's. It works fine as long as only one thermocouple is attached to the pot, but as soon as I touch the 2nd one to the pot both PID'S error out.
Any idea why this would be and what I can do about it? Seems like it may be a grounding issue but it still did it with a better ground.

Thanks,

Mike

 

[trimixdiver1]

I just built a controller using 2 JLD612 PID's. It works fine as long as only one thermocouple is attached to the pot, but as soon as I touch the 2nd one to the pot both PID'S error out.
Any idea why this would be and what I can do about it? Seems like it may be a grounding issue but it still did it with a better ground.

Thanks,

Mike

Sounds like a ground loop. Both wires on the tc need to be isolated from ground and each other. Also are the tc's grounded or not? I mean the type not if they actually are.

http://www.omega.com/techref/themointro.html

 

[McRoth]

Good question. These are the ones I purchased 251297557927 from eBay. They are type k, but the description doesn't say anything about grounding. Probably have to find the right ones now. Thx.

 

[McRoth]

I've got a bcs controller probe from brewer's hardware that I'm trying to wire in to see if that'll fix the problem but I can't get it to read anything from it. It has 3 wires, red white and black. I've tried hooking them upv every way I can but no go. As near add I can tell they are supposed to be pt100 sensors. Anyone know what I'm doing wrong? I set the controller to pt100.

Thx

 

[trimixdiver1]

I've got a bcs controller probe from brewer's hardware that I'm trying to wire in to see if that'll fix the problem but I can't get it to read anything from it. It has 3 wires, red white and black. I've tried hooking them upv every way I can but no go. As near add I can tell they are supposed to be pt100 sensors. Anyone know what I'm doing wrong? I set the controller to pt100.

Thx

Are you sure it's a RTD? If so then one wire is on one side of the resistor and the other two are in parallel from the other side. Now a red and white could also be a J thermocouple. The black could be ground.

 

[McRoth]

The part number on the bag has pt100 in it and the website says it's a thermistor. I'll give j a try just in case though.

 

[trimixdiver1]

The part number on the bag has pt100 in it and the website says it's a thermistor. I'll give j a try just in case though.

If it says PT 100, it's an RTD

http://www.pyromation.com/Products/Rtd.aspx

This wave of Chinese crap is really making things hard on users.

Normally a RTD has a white and two reds. A thermistor

http://en.m.wikipedia.org/wiki/Thermistor

Is just a pair of wires

Your talking about 3 different devices that all give a different output.

An RTD and thermistor are resistance vs temp, but different curves.

A thermocouple gives a millivolt output vs temp. Each type give a different curve and range depending on the type (material)

http://www.omega.com/techref/colorcodes.html

 

[McRoth]

I received my ungrounded thermocouples yesterday and they solved the problem!
Never did hear back from brewer's hardware. Going to have to call them.

 

[trimixdiver1]

I received my ungrounded thermocouples yesterday and they solved the problem!
Never did hear back from brewer's hardware. Going to have to call them.

Good to hear