S7-200 auto detects broken 4-20 mA current loop ?

Which particular Siemens card are you talking about ?

Broken Sensor Protection on thermocouple circuits has long since been a
   feature of most systems, presumably because of their tendancy to fail
and the need to create an alarm or trip. It is normally done via a
separate monitoring signal that causes the signal to go hard to top or
bottom of the scale depending on the application.


Steve
www.mtl-inst.com



ebriosso@gmail.com wrote:

ebriosso@gmail.com wrote:

If a 4-20mA analogue input is 0 or 25mA the sensor is broken

If you really want a seperate alarm then put in a trip amplifier

Not necessarily, 0mA could imply open circuit cabling, 25mA could mean a
short circuit.

Also some intelligent transmitters can be configured to fix the output
current at specific current levels corresponding to detected faults, ie
a broken thermocouple in the case of a temperature transmitter. The
system is then programmed to display specific error messages.

Steve
www.mtl-inst.com

Yes, The statement 'the sensor is broken' is a bit of a generalisation from
the sensors POV

 'the sensor loop is broken' is better...I meant to imply that 0 and +24mA
are common and easily detectable fault conditions in an analogue loop...for
which the cabling is the most likely culprit


Now that would be handy