Cold junction compensation

You can set the cold junction compensation type for each channel individually in the parameters 80n0:0Chex "Coldjunction Compensation.

The possible values for these parameters are described below.

Value 0 "intern"

In the factory setting, all parameters 80n0:0Chex are set to "intern". With this setting, the cold junction temperature is measured individually at each channel.

A Pt1000 measuring resistor must also be connected to each channel to which a thermocouple is connected. See Connection example 1.

Value 1 "none"

No cold junction compensation is performed.

Value 2 "external process data (1/100°C)"

This setting is intended for a situation where the cold junction temperature is measured with a separate measuring device, for example.

Enable the process data 0x1600 to 0x1603 in the Process Data tab. You can transfer the externally measured cold junction temperatures to the box via the process data objects "TC Outputs Channel n".

Value 3 "by coldjunction temp. of channel 1"

With this setting, the cold junction temperature of channel 1 is used for cold junction compensation of the other channels. This saves the costs of a separate Pt1000 resistor for each channel. See Connection example 2.
However, large measuring errors can occur with this setting. The setting is only recommended if the temperature difference between the cold junction of a channel and the cold junction of channel 1 is constant.

Example: Enabling the cold junction of channel 1 for channel 2

1. Make sure that the temperature difference between the cold junctions of the channels is as constant as possible.
2. Set the parameter 8010:0Chex "Coldjunction Compensation" to the value "by coldjunction temp. of channel 1".
3. Determine the constant temperature difference between the cold junctions of channel 1 and channel 2:
Tdelta = TV1 – TV2
If the cold junction of channel 1 is warmer than that of channel 2, the value Tdelta is positive.
4. Enter the temperature offset in parameter 8010:1Chex "Coldjunction temperature offset from channel 1". The unit is 1/100 °C.
Example: for a temperature difference of 0.5 °C enter the value 50 here.

The procedure is the same for channels 3 and 4. The corresponding parameters are: