WIKA TR21 Mode D'emploi page 14

5. Commissioning, operation
5.3 Behaviour of the electrical output signal
Sensor break and short circuit
■
Sensor break or short circuit are signalled after positive detection (after
EN
approx. 1 second). If this fault condition has been caused by a malfunction, then
a relevant measuring signal must exist for approx. 1 second in order to return to
measuring mode. From the time of the error detection up to the error signalling, the last
relevant measured value will be delivered on the current loop.
Therefore, in the event of a "true" sensor break or short circuit, this is also signalled
permanently. In the event of a "false" sensor break or short circuit, the transmitter has the
possibility of reverting to measuring mode.
Medium temperature outside the span
■
If the medium temperature exceeds that configured within the transmitter, the transmitter
will operate in a linear fashion within the following limits: 3.8 mA (MRS); 20.5 mA (MRE).
If these limits are exceeded, then an error will be signalled.
Hysteresis on return to the measuring span
■
After the linear error limits have been exceeded, on return to the measuring span, a
hysteresis of 0.1 mA must be passed. This hysteresis prevents the transmitter from
jumping back and forth between error and measuring mode.
Error signalling
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3.8 mA 4 mA
Error
3.8 ...
signalling
4 mA
3.9 mA
Error limits and permissible measuring range
20 mA
4 ... 20 mA
20 ... 20.5 mA
Measuring mode
WIKA operating instructions model TR21
20.5 mA
Error
signalling
Error signalling
20.4 mA