Appendix A: Technical reference
A.3 Analog Output
SITRANS LR250 with mA/HART
Operating Instructions, 10/2019, A5E32220602-AG
241
A.2.9 Damping
Damping Filter (2.2.4.) smooths out the response to a sudden change in level. This is an
exponential filter and the engineering unit is always in seconds.
In 5 time constants the output rises exponentially: from 63.2% of the change in the first time
constant, to almost 100% of the change by the end of the 5th time constant.
time constant = 2 seconds
input (level) change = 2 m
A.3 Analog Output
The mA Output (current output) is proportional to material level in the range 4 to 20 mA. 0%
and 100% are percentages of the full-scale reading (m, cm, mm, ft, in). Typically mA output
is set so that 4 mA equals 0% and 20 mA equals 100%.
When SITRANS LR250 is put into PROGRAM mode (for example, by navigating through the
menu) it stops updating the output of the device (local user interface and mA Output). It
stores the most recent measurement, and holds the associated readings and mA signal
output. The device reverts to the parameter last addressed during the previous program
session.
When the device is returned to Measurement mode, the transceiver resumes operation. The
reading and mA output default to the last measurement taken. The reading and associated
outputs migrate to the current process level at a rate controlled by
Response Rate (2.4.1.).
If the device is left in PROGRAM mode for 10 minutes without input, it automatically reverts
to
Measurement mode.
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