Parameterization And Programming; Basics Of The Measurement Functions; Data Processing - Beckhoff ELX3312 Operating Manual

Parameterization and programming

5 Parameterization and programming
5.1

Basics of the measurement functions

The measuring functions of the ELX331x can be described as follows:
• The internal electronics records the differential voltage of a channel between the respective terminal
points +TCn and -TCn.
• This measured variable is the voltage resulting from the thermoelectric effect at the measuring point of
the sensor, provided that no further thermoelectric transitions or external voltages are applied.
• The reference junction of the respective channel is located in the immediate vicinity of the two
associated terminal points inside the device; the reference temperature is continuously determined
electronically.
• The change of the differential voltage as a function of the temperature is - depending on the
thermocouple - typically in the range of a few µV to mV and is detected precisely by the electronics.
• Measurement and comparison temperatures are calculated internally using characteristic curves stored
for the selectable thermocouple types and a temperature is output as the process date.
• Data processing is subject to IIR/FIR filters on the software side, if activated.
• Wire breakage detection is performed by injecting a low DC current (below 1 mA) into the respective
channel at regular intervals.
5.2

Data processing

Fig. 42: ELX331x - Data flow
56 Version: 1.3.0 ELX3312 and ELX3314