Data logger reference
If the reference junction is at the data logger, matching thermocouple wire should be run between the COM terminals of the multiplexer and the differential input channel on the data logger (observe TC wire polarity).
The CR6, CR3000, CR1000X, CR800-series, CR300-series, and CR1000 have built-in temperature references.
The measurement from the CR6 and CR300 PanelTemp() instruction does not accurately reflect the temperature of the wiring panel, since it measures the temperature of the main processing board. Therefore, if the processor or charge (CHG) input are active, the PanelTemp measurement will be warmer than ambient. This should be taken into consideration if this measurement is used as a reference temperature for thermocouples.
When the reference junction is located at the data logger, the signal wires between the data logger and the AM16/32B must be of the same wire type as the thermocouple (Differential thermocouple measurement with reference junction at the data logger). The “polarity” of the thermocouple wires must be maintained on each side of the multiplexer (for example, if constantan wire is input to an L terminal, then a constantan wire should run between the multiplexer COM ODD L terminal and the data logger measurement terminal). Differential thermocouple measurement with reference junction at the data logger and Differential thermocouple measurement with reference junction at the AM16/32B (using 107-L thermistor) depict type T thermocouple applications, but other thermocouple types (for example, E, J, and K) may also be measured and linearized by the data loggers.
It is not recommended to make measurements of any other sensor type through the AM16/32B if thermocouples are measured with respect to the data logger reference (the signal wires between the data logger and AM16/32B are made of thermocouple wire). Two problems would arise due to the properties of thermocouple wire.
First, an extraneous thermocouple voltage would be added to the non-thermocouple signal at the junction of dissimilar metals (for example, the multiplexer COM terminals). The magnitude of this signal would vary with the temperature difference between the data logger and the AM16/32B.
Second, some thermocouple wires have a greater resistance than copper, which adds resistance to the non-thermocouple sensor circuit. For example, constantan is approximately 26 times more resistive than copper.
