What are the functions of HART communicator? How to use it for Zero trim & D/A trim?

Functions of HART communicator:

  • The main function of the HART 375 Communicator is to communicate with an instrument based on the HART protocol.
  • Provide identification details of the instrument being evaluated. The identification includes the type of instrument, sensor type, model no, etc.
  • Can name/tagging or change for each HART instrument.
  • Can perform diagnostic abnormalities of each HART instrument
  • Can make adjustments for URV (Upper Range Value), LRV (Lower Range Value).
  • Can monitor Variable Process values and signal values mA.
  • Can be used to reset and setup the reading value during calibration.
  • Can be used to give the Auto-Manual Calibration command for the control valve.
  • Can be used to determine Equal Percentage, Linear, and Quick Opening from the Control Valve.
  • Can do signal injection for simulation.

Hart Protocol provides two simultaneous communication channels, 4-20mA analog signals and digital signals.

4-20mA signal communicates the main values ​​measured (in this case instrument devices in the field) using a 4-20mA signal loop. Additional information from the device is communicated using digital signals superimposed on analog signals.

Digital signals contain information from the device (device) including device status, diagnostics, additional measurement values ​​or calculated values, etc.

The use of these two communication channels provides a cost-effective solution, and a complete and powerful communication solution that is easy to use and configure.

Zero trim:

Image result for hart communicator 375 zero trim

The meaning of the zero trim is setting the transmitter on the reading value of the Zero input. ZERO trim adjusts input from the transmitter using exactly ZERO standard values.

For example pressure transmitter zero pressure is when isolating the process and connecting to the vent. Then when that condition of Communicator 375 apply ZERO trim. Communicator 375 must show the ZERO value.

D/A trim:

The D/A trim means setting the transmitter at the signal OUTPUT value of 4-20 mA. No input from the process required. D / A trim only use a multimeter to measure current 4-20 mA.

Use the D/A trim menu on the Communicator 375 which will instruct the (Digital Command) transmitter to produce 4-20 mA (Analog Output).

Your multimeter as a calibrator that will validate the current value. Adjustments can be made from the communicator if current values are not the same as those ordered by the communicator via digital data.


Instrumentation Engineer

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