WIKA TR31-3 Operating Instructions Manual page 23

6. Commissioning, operation
6.3 Behaviour of the electrical output signal 4 ... 20 mA
Sensor break and short-circuit
■
Sensor break or short-circuit are signalled after positive detection
(after approx. 1 second). If this fault condition has been caused by
a malfunction, then a relevant measurement signal must exist for
approx. 1 second in order to return to measuring mode. From the time
of the error detection up to the fault signal, 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 media temperature configured in the transmitter exceeds
the span, 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.
3.8 mA
Error
signalling
Error signalling
3.9 mA
Error limits and permissible measuring range
WIKA operating instructions models TR31-3, TR31-K
4 mA
3.8 ...
4 ... 20 mA
4 mA
Measuring mode
20 mA 20.5 mA
20 ... 20.5 mA
signalling
Error signalling
20.4 mA
EN
Error
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