Pressure Transducers Output Check Up.

If the pressure transmitters (PT) are industrial transmnitters, they will have a pair test terminals under the screw cover. A milliampmeter placed across the test terminals will indicate the loop current without opening or breaking the loop circuit to place the meter in series in the circuit to read the current.

Otherwise, you'll have to lift a wire in the loop at some connection point (open the circuit) and insert the milliampmeter in series. The current will read negative if the meter is connected backwards.

If you can determine the analog input's resistance, then you can read the voltage across the analog input and calculate the current with Ohms Law. Many industrial analog inputs use 250 ohms which drops 4-20mA as 1.0-5.0 volts, but others don't.

The same measurement techniques apply for temperature transmitters with RTD inputs, except for test terminals which are not as common on temperature transmitters.

To test an RTD, you measure its resistance and look it up on a resistance vs temperature table/chart. You need to know what kind of RTD it is. 100 ohm (at freezing) are typical industrial RTDs, HVAC uses 1000 ohm, there are others.