Introduction
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.
