Answer / carl_ellis

Any 2 wire, loop powered 4-20mA transmitter that puts out
30mA is broken. The only transmitter that puts out 30mA is
a legacy 10-50mA transmitter from 20-30 years ago.

While the upper end of the 4-20mA signal range is 20.0mA,
most 2 wire, loop powered transmitters allow for some slight
signal over-range, typically 20.5mA.

NAMUR standards use 21.0 mA to signal a fault or failure
mode. Other vendors use other values, 20.8mA, 21.2mA or
some value in the range of 21mA. But no vendor uses 30mA
as a fault mode.

The transmitter is broken or dysfunctional.

Carl Ellis
Measure First

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