Troubleshooting of a transmitter


In this session we are gonna discuss about troubleshooting of a transmitter.we are gonna look into some common problems and their solutions .

What are the troubleshooting when Transmitter milliamp reading is zero

  • Verify power is applied to signal terminals
  • Check power wires for reversed polarity
  • Verify terminal voltage is 10.5 to 42.4 V dc
  • Check for open diode across test terminal

Transmitter Not Communicating with HART Communicator

  • Verify the output is between 4 and 20 mA or saturation levels
  • Verify clean DC Power to transmitter (Max AC noise 0.2 volts peak to peak)
  • Check loop resistance, 250 Ω minimum (PS voltage -transmitter voltage/loop current)
  • Check if unit is addressed properly

 Milliamp reading is low or high Verify applied pressure

  • Verify applied pressure
  • Verify 4 and 20 mA range points
  • Verify output is not in alarm condition
  • Verify if 4 – 20 mA output trim is required

Transmitter will not respond to changes in applied pressure

  • Check impulse piping or manifold for blockage
  • Verify applied pressure is between the 4 and 20 mA set points
  • Verify output is not in alarm condition
  • Verify transmitter is not in Loop Test mode

Digital Pressure Variable reading is low or high

  • Check test equipment (verify accuracy)
  • Check impulse piping for blockage or low fill in wet leg
  • Verify transmitter is calibrated properly
  • Verify pressure calculations for application

Digital Pressure Variable reading is erratic

  • Check application for faulty equipment in pressure line
  • Verify transmitter is not reacting directly to equipment turning on/off
  • Verify damping is set properly for application

Milliamp reading is erratic

  • Verify power source to transmitter has adequate voltage and current
  • Check for external electrical interference
  • Verify transmitter is properly grounded
  • Verify shield for twisted pair is only grounded at one end


How to Remove a transmitter from Service ?

• Follow all plant safety rules and procedures.
• Isolate and vent the process from the transmitter before removing the transmitter from service.
• Remove all electrical leads and conduit.
• Detach the process flange by removing the four flange bolts and two alignment screws that secure it.
• Do not scratch, puncture, or depress the isolating diaphragms.
• Clean isolating diaphragms with a soft rag and a mild cleaning solution, and rinse with clear water.
• Whenever you remove the process flange or flange adapters, visually inspect the Teflon o-rings. Replace the o-rings if they show any signs of damage, such as nicks or cuts. Undamaged o-rings may be reused.


Also read 

Calibration procedure of DPT transmitter

How to calibrate RTD transmitter

How to calibrate a Pressure gauge.

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