I'm trying to setup a temperature data logger using Graphtec GL240. I will be using K-type thermocouples for the logger. I want to run short length of k type cables from the logger to a female K type plug and then create another set of wires with a male plug (I am doing this because it will allow me to swap wires easily).

Will this affect the accuracy of the logger?

Will be using this setup to calibrate an oven.

  • \$\begingroup\$ As long the wire materials are the same (and of course connector material) it will not affect it. \$\endgroup\$ – Marko Buršič Aug 7 '19 at 9:23
  • \$\begingroup\$ Will you be calibrating the logger itself? And how accurate does it need to be? There will be some very minor effects from using plugs, but these can be calibrated out, and if your accuracy specs aren't tight then it won't really affect you \$\endgroup\$ – MCG Aug 7 '19 at 9:39
  • \$\begingroup\$ @MarkoBuršič Thank you \$\endgroup\$ – DrakonianD Aug 7 '19 at 22:59
  • \$\begingroup\$ @MCG Logger will be calibrated to Temp. by an accredited lab But I am planing to send the unit for calibration after I setup the unit with plugs \$\endgroup\$ – DrakonianD Aug 7 '19 at 23:00
  • \$\begingroup\$ @DrakonianD thats a good way to do it. Just remember, if you do replace the probe, using a new plug, there will be subtle differences. But depending on your accuracy needs, it may well be negligible \$\endgroup\$ – MCG Aug 8 '19 at 7:36

So long as you are using Thermocouple Connectors that match your thermocouple wire AND the extension wires also match the thermocouple wires AND you get the polarity of the connectors correct, you will not have any problems.

It is important that the metals used throughout the entire chain from the thermocouple junction all the way to the input of the data logger are consistent. That is: each conductor is of the same metal type from end to end.

As you are probably aware, a thermocouple consists of two different metals brought together in a junction. It is at that junction where the temperature is is measured.

More accurately, the temperature is measured between that junction and the other end of the thermocouple wires. That other end of the thermocouple wires is referred to as the "Cold Junction". Your data logger has another temperature sensor at that "Cold Junction" that adds to or subtracts the ambient temperature from the temperature difference between the thermocouple junction and the input of the data logger. Google is your friend if you need more information about how thermocouples measurements work.

Bottom line: so long as the metals in each of the thermocouple wires is the same from the measuring junction to the data logger, you can be assured of accurate measurements.

One common cause of thermocouple measurement errors is to get the polarity of the thermocouple connectors backwards. Another cause of errors is that the extension wires don't match the thermocouple wires.

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  • \$\begingroup\$ Thank you for the well explained answer @Dwayne. I am planing to use K-type T-C wires for both. \$\endgroup\$ – DrakonianD Aug 7 '19 at 22:59

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