Beckhoff ELX3312, Руководство по эксплуатации

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Parameterization and programming
ELX3312 and ELX3314 56 Version: 1.3.0
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
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