Bench Test Panel for Different Thermocouples

Hi
I have been asked to build a panel for pre-testing heater-bands on different extrusion heads, unfortunately within the factory we use both J Type and K Type thermocouple.
With 8 heaters to control and 8 Eurotherm 2204E controllers to control them I was hoping to avoid having to change the Type in each controller each time a head is changed, is it possible to add anything inline with one of the thermocouples so that the controller sees the same output from each thermocouple type?
My initial thoughts are a voltage divider of some type, possibly using a potentiometer brought inline with a toggle switch for each circuit.
The purpose of the test bench panel is only to preheat the units to an approximate temperature so an error of +/- 5 degrees would not be considered an issue.
Many thanks in advance
David Earley
 
What's your budget? Can the Eurotherms use a 4-20mA signal instead of TC? If so, consider a couple of temperature transmitters, maybe something like this:

https://www.automationdirect.com/ad...ple_input)/connection_head_mount/xth-01000f-k

(no endorsement of that product, it's just an example I found quickly)
Have 2 transmitters with a switch like you're talking about to connect the right one to the controller. The controller will see a 4-20mA signal regardless of TC type.
 
What's your budget? Can the Eurotherms use a 4-20mA signal instead of TC? If so, consider a couple of temperature transmitters, maybe something like this:

https://www.automationdirect.com/ad...ple_input)/connection_head_mount/xth-01000f-k

(no endorsement of that product, it's just an example I found quickly)
Have 2 transmitters with a switch like you're talking about to connect the right one to the controller. The controller will see a 4-20mA signal regardless of TC type.
My colleagues and I have been kicking this problem around for a few days, not one of us came up with such a straight forward idea, unfortunately the only input we have is for Type K thermocouple, but thank you for taking the time to reply.
 
Hmmm....that complicates things a bit. I looked briefly but couldn't find a signal converter that goes the other way (analog signal to TC). Or

The type J/K TCs have different zero points and scales, which makes conversion a little more complicated than just using a voltage divider. For the same temperature, the type J will be at a higher voltage, so you may be able to use a voltage divider (like a pot) to get it to work well enough close to your operating point but accuracy will decline as the temperature varies from your calibration point.
 
Check the manual and spec again. The spec sheet for the 2204E says that it has "Universal Inputs" including milliamp input.

2204E has universal inputs.JPG

The conventional understanding of the term "Universal Inputs" is that one input type from the many available input types is selected in the configuration and the physical wiring has to match the selected input type.

In this case a milliamp input needs a 2.49 Ohm precision resistor across the (+) and (-) input terminals.

2204E input wiring.JPG
 
Dear David,

We work a lot with various thermocouples of various types.
Always remember that you have to use the cable and connectors for that specific thermocouple type if you want to measure correctly. Otherwise you will have a temperature deviation. But if it is not such a big problem you can use the same, when it is only for a quick check for functionality of the heating element.

You could consider using a temperature controller that makes use of 2 thermocouple inputs that can be switched with a digital input (or via communication via Modbus, what you prefer).

See for example the FZ400/900: https://cascade.net/en/fz-series/

We make use of this functionality in lots of situations and help you with that. Also with the thermocouple cables and connectors of all types.

And as mentioned above, you could make use of a thermocouple to 4-20mA convertor for each thermcouple type and connect the one you use to the controllers input. You must set the temperature that corresponds to the 20mA signal to to the temperature that corresponds with it in the temperature controller. See: https://cascade.net/en/transmitter/

Best regards,
Patrick
 
Thank you to everyone that has replied. The apprentices who have been given this challenge will be assembling a test rig over the next few days to see what error we get at the 200 degree target, if we are within 20 degrees then this will be acceptable. We are using a calibrated heat source designed for testing thermocouples so they have a good basis to test from. I will update the forum when we have some results.
 
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