I have a single channel temp gauge using a 4 pole, 6 throw, two section manual switch to monitor 4 different temp probes.
I'm looking for a switching relay or ? to automaticly switch between the 4 probes.
The probes are 2 wire K type thermocouples.

It would be really nice if you could change switching speed and an led to show what channel it's on.

Any ideas?

TIA

 

Switching a Type K TC and doing it electronically you want a Thermocouple Multiplexer. You don't mention how electronically you want to select one of four active thermocouples? You also do not mention with your existing switch how you are addressing CJC (Cold Junction Compensation) of your existing thermocouples? I assume you are using a switch designed for switching thermocouples? I would start with a Google of Thermocouple Multiplexer based on what you have mentioned. I would look to distributors like Omega Engineering for starters.

Ron

 

Back in the 1980's, I had exactly that a work for about 10 channels or so. It was a large clunky box maybe 8x10x3" tall, but it worked. Exposed terminals at the bottom of the top with red LED's. You could set the number of TC's to scan, the rate and you could stop the scanning.

I had to modify them because the regulators were not populated. they blew up when used next to 1000 W IR heaters.

Connections basically need to be isothermal

 

Looks like they do exist, but with monitoring and graphing options. I found this https://www.hgsind.com/product/pmd-...uple?st-t=adwords&vt-k=+thermocouple +scanner

 

Looks like they do exist, but with monitoring and graphing options. I found this https://www.hgsind.com/product/pmd-mxt-8-16-24-or-32-channel-digital-temperature-scanner-universal-thermocouple?st-t=adwords&vt-k=+thermocouple +scanner

Yeah, they have come a long way. I worked with some of the old Omega and similar units which would scan channels and print. The stuff was old but it worked fine till we replaced the stuff. Some of it was actually pretty cool equipment.

Ron

 

I did a fair amount of PID tuning using a strip chart recorder and the analog out of a temperature controller or a multi-type thermocouple type Fluke thermometer. I standardized our Eurotherm stuff with sp in, sp out and (measured value out) and the ability to do current limit. They had propreitary direct dual SCR outputs.

Then I added a 3AG fuse in series with the $25.00 fuse. When I did that, the $1.00 blew. The wiring was in a vacuum chamber, so all exposed.
I set everything up with current limit too. They were nice and gave us schematics, so I could convert the non-conforming ones. We ran these into variacs.

Omega was pretty good at the time too. I easily got schematics for temp meters and the scanner we used. I added analog out to the temp meters. It was an option and modified the scanner so it would not die. A couple of transorbs.

Then Eurotherm came out with their 818 programmable controller and that changed history. There is an entire config manual and a config key.
The output was isolated and sensible with RS485 control.

Then I changed history again by insisting that they could replace a home built variac with meters with a DC power supply.
I wasn;t allowed to get the isolated DC 0-5V outputs or any other control options. I'm not sure if you could use 0-5V in and interogate V and I using an interface like RS485 or IEEE488 anyway.

A gizmo that could measure 0-120V or 0-40 V and 0-5V in a couple of ranges for current would have been really neat.
The reference was always the positive output of the supply which would cause endless grief.