Flow Transmitter Calibration and Troubleshooting Guide
Calibration ensures flow transmitters provide accurate measurements over their entire operating range. Regular calibration is essential for process control integrity.
I. Calibration Procedures
Analog Output Calibration
- Connect a precision multimeter in series with the loop to measure output current
- Apply a known input corresponding to zero flow (LRV) and adjust the zero trim until the output reads exactly the low output value
- Apply a known input corresponding to full scale (URV) and adjust the span trim until the output reads exactly the high output value
- Verify linearity at intermediate points (25, 50, and 75 percent of range)
- Document all calibration results including as-found and as-left values
Digital Calibration (Smart Transmitters)
- Connect the HART communicator or configuration software
- Perform sensor trim by applying known flow values and adjusting the digital reading
- Perform output trim to align the analog output with the digital reading
- Verify both digital and analog readings across the full range
II. Loop Testing
- Place the control loop in manual mode before testing
- Use the transmitter's loop test function to force specific output values
- Verify the control system receives the correct values at each test point
- Return the transmitter to normal operation and verify process readings
III. Troubleshooting
Fixed Output: Check if transmitter is in manual or multidrop mode. Verify sensor connection.
Erratic Output: Check for electrical noise or intermittent connections. Increase damping if process is inherently noisy.
Output Saturated: Verify that the process flow is within the configured range. Check for sensor damage or electronic failure.
