Question on instrument calibration please?

Hi Friends,


Please, I need clarification on two things:


1. I understand trimming via Zero and SPAN adjuster, BUT what MENU on Emerson 475 Field Communicator is used for Trimming?


2. For 475, Do I need to physically introduce 250-ohm Resistor on the Positive side of the the Loop? I was told that 475 has in-built 250-ohm Resistor that eliminates the need, is this true?


3. How do one differentiate between HART and FIELDBUS Transmitter?


Thanks in advance

1) What is trimming in Instrumentation terms?

2) Did you read the manual? The leaflet mentions this resistor as a spare part, so chances are that it isn't included and came in the box with the communicator.

3) HART runs on a 4-20mA loop and modulates digital data on top of the analog signal. A fieldbus is a digital communication protocol which will run on whatever media was defined for it... RS232, 422, 485, Ethernet, etc, etc...

The device model/part number is different for HART or Foundation Fieldbus.


The quick way is whether the transmitter is 4-20mA or some digital signal.


HART is 4-20mA. Digital is Foundation Fieldbus or Profibus.

cardosocea said:

1) What is trimming in Instrumentation terms?

2) Did you read the manual? The leaflet mentions this resistor as a spare part, so chances are that it isn't included and came in the box with the communicator.

3) HART runs on a 4-20mA loop and modulates digital data on top of the analog signal. A fieldbus is a digital communication protocol which will run on whatever media was defined for it... RS232, 422, 485, Ethernet, etc, etc...

Click to expand...

Hi Friend,
Sorry if I'm wrong, by Trimming I mean: assuming with my calibrator I input the LRV of Psi expecting a 4mA output from the Transmitter and found out that deviates, how do I make adjustment using 475 (not 0 & span button)? What menu on 475 please?

There is no 'standard' menu for HART devices.


Menu navigation depends on the specific device, which is manufacturer-specific. You need the manual that covers the HART calibration method for that device.