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MAINTENANCE | Melt Pressure Transducer/Transmitter Calibration Checklist

  • Writer: Bob
    Bob
  • Aug 30
  • 2 min read
Representative maintenance checklist illustrated

1. Tools & Equipment Needed

  • NIST-traceable pressure calibrator (hydraulic hand pump + reference gauge, or deadweight tester)

  • Temperature-controlled barrel/extruder (must be at normal operating temperature)

  • Multimeter or calibration reader (for mV/mA/V sensors)

  • Portable calibrator/communicator (for smart transmitters w/ HART, Profibus, etc.)

  • Clean lint-free wipes and approved cleaning tools for sensor port

  • Calibration log sheet or digital CMMS entry system


2. Preparation

☐ Verify that the process barrel is heated to normal operating temperature.

☐ Remove material pressure from the barrel (ensure extruder screw is idle).

☐ Inspect sensor port for debris, damage, or leftover polymer—clean if necessary.

☐ Confirm reference calibration device is within valid certification date.

☐ Allow sensor to stabilize for 20–30 minutes at operating temperature.


3. Zero Calibration

For all sensor types

☐ With no material pressure on the diaphragm:

  • Set controller/indicator to 0 psi (0 bar).

  • If using a transmitter, adjust zero trim.

  • For digital transmitters, use “Zero Trim” in software/communicator.


    ☐ Record the zero value in the log sheet.


4. Span Calibration

A. Strain Gauge / mV Output Transducers

☐ Connect calibrator and apply a known reference pressure (e.g., 5,000 psi).

☐ Measure mV signal and compare to expected value (e.g., 2 mV/V output).

☐ Adjust gain/scale on controller so displayed reading matches reference.


B. Amplified Transmitters (mA or V)

☐ Apply reference pressure.

☐ Verify output:

  • 4 mA (or 0 V) = 0 psi

  • 20 mA (or 10 V) = full-scale psi (e.g., 10,000 psi)

    ☐ Adjust span trim until transmitter output matches reference pressure.


C. Smart Digital Transmitters

☐ Use communicator to run Zero Trim at no pressure.☐ Apply reference pressure OR simulate span test electronically.☐ Adjust Span Trim digitally to align with standard.


5. Validation

☐ Remove pressure and verify that reading returns to zero.

☐ Apply intermediate pressure point (25% or 50% FS) and confirm linearity.

☐ Repeat for 75% FS.

☐ If non-linear, investigate sensor damage or port blockage.


6. Documentation

☐ Record:

  • Sensor ID / location

  • Date & technician

  • Reference equipment used (serial #, calibration due date)

  • Zero & span results (before and after adjustment)

  • Pass/Fail status

☐ Store records in calibration logbook or CMMS system.


7. Frequency Guidelines

  • Plastics extrusion:

    • Quick zero check → daily or after each cleaning

    • Full calibration → every 6 months

  • Food processing:

    • Zero check → weekly/startup

    • Full calibration → every 3 months (per audit requirements)

    • Annual factory re-calibration


GOAL: A transducer/transmitter with traceable, verified accuracy for both quality and compliance.

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