— Common Pressure Measurement Problems and Solutions
Pressure transmitters are among the most frequently used instruments in industrial automation. However, during long-term operation, various issues can arise due to process changes, environmental influences, improper installation, etc., leading to control deviations, false alarms, or even process shutdowns.
Based on nearly five decades of experience in manufacturing and servicing pressure instruments, Anhui Tiankang (Group) Co., Ltd. presents a systematic overview of common pressure measurement problems, their root causes, and field-proven solutions to help you quickly diagnose and resolve issues.
1. Quick Reference Table of Common Problems
| Symptom | Possible Cause | Quick Check |
|---|---|---|
| Output always 4 mA (or lower limit) | No pressure, sensor damaged, power failure | Check supply, apply pressure, see if output changes |
| Output always 20 mA (or upper limit) | Over-range, sensor overload, short circuit | Check if pressure exceeds range, disconnect load |
| Output fixed at a value, no change with pressure | Circuit failure, sensor stuck | Replace or bench test |
| Reading jumps / unstable | Electrical noise, pulsating media, loose wiring | Check shield grounding, add damping, tighten terminals |
| Zero drift (output not 4 mA at zero pressure) | Mounting stress, temperature change, diaphragm damage | Check torque, re-zero |
| Consistent offset (reading too high or low) | Range wrong, impulse line clogged/leaking | Re-range, check impulse lines |
| Slow response | Damping too high, impulse line clogged, long capillary | Reduce damping, clean impulse lines |
| Drift with temperature | Ambient temperature change, no temperature compensation | Use compensated transmitter, insulate |
| Frequent failure in wet/corrosive environment | Ingress protection insufficient, seal failed | Upgrade to IP68 / corrosion-resistant type |
| IS loop no output or abnormal | Safety barrier fault, excessive cable capacitance | Check barrier, verify IS parameters match |
2. Detailed Problem Analysis and Solutions
Problem 1: Output always 4 mA (or lower limit)
Symptoms: Output stays at 4 mA (or set lower limit) regardless of pressure change.
Possible causes:
No power or power supply failure
Open circuit or poor contact
Sensor diaphragm ruptured or severely damaged
Pressure not reaching transmitter (root valve closed, impulse line blocked)
Troubleshooting steps:
Measure voltage at transmitter terminals (should be ≥24V DC).
Check for open circuit or loose terminals.
Apply manual pressure (e.g., hand pump) and observe output. If no change, transmitter may be faulty.
Check if root valve is open and impulse line is clear.
Solutions:
Restore power, rewire.
Replace damaged transmitter.
Open root valve, clear impulse line.
Problem 2: Output always 20 mA (or upper limit)
Symptoms: Output stuck at 20 mA (or set upper limit), no change with pressure.
Possible causes:
Actual pressure exceeds range (overload)
Sensor damaged due to overpressure (permanent deformation)
Output short circuit (current cannot drop)
Range set too low, normal pressure already exceeds span
Troubleshooting steps:
Confirm actual pressure is within range. If over-range, relieve pressure.
Isolate pressure source, vent to zero, observe if output drops. If not, sensor may be damaged.
Disconnect load and measure transmitter output directly. If still 20 mA, internal fault.
Solutions:
Re-range to match actual pressure.
Replace damaged transmitter.
Check for short circuit in loop.
Problem 3: Unstable / fluctuating output
Symptoms: Output values fluctuate randomly; control room display jumps.
Possible causes:
Electrical interference (VFDs, motors, radio)
Loose wiring or poor grounding
Pulsating media (pump discharge, reciprocating compressor)
Bubbles or condensate in impulse line (for gas service)
Debris or corrosion on diaphragm
Troubleshooting steps:
Measure current directly at transmitter terminals and compare with control room reading. If stable locally but jumping in the control room, interference is on the signal path.
Check that shield is grounded at one end only.
Observe if a local pressure gauge also jumps. If yes, media is pulsating.
Check impulse lines for liquid or gas pockets.
Solutions:
Ground shield at one end; separate signal cables from power cables.
Increase damping (via transmitter damping setting or add snubber).
Install pulsation dampener or needle valve.
Bleed impulse lines.
Clean diaphragm surface.
Problem 4: Zero drift (output ≠ 4 mA at zero pressure)
Symptoms: Output deviates from 4 mA when transmitter is vented (gauge type) or evacuated (absolute type).
Possible causes:
Excessive mounting torque causing housing deformation
Temperature change causing diaphragm or fill fluid expansion
Debris or coating on diaphragm
Long-term sensor drift
Troubleshooting steps:
Close root valve, open vent/drain valve to vent to atmosphere.
Measure output current.
Use zero adjustment (screw or communicator).
Solutions:
Perform zero calibration (note: for IS loops, do so in safe area or with IS communicator).
If drift persists after zeroing, sensor may be aged or damaged; replace.
Avoid over-tightening during installation; use uniform gasket compression.
Problem 5: Consistent offset (reading too high or too low)
Symptoms: Transmitter reading has a fixed proportional error compared to actual pressure.
Possible causes:
Range set incorrectly
Impulse line partially blocked or leaking (one side blocked for DP)
Media density different from design (level measurement)
Elevation difference between transmitter and tap point (no migration)
Troubleshooting steps:
Read current range setting via communicator; verify against design.
Check impulse lines for blockage or leaks.
For level measurement, verify actual media density.
Check if transmitter is below or above tap point; calculate static head.
Solutions:
Re-range correctly.
Clean or replace impulse lines.
Perform zero migration (positive or negative) to compensate static head.
If density varies frequently, consider switching to radar level.
Problem 6: Slow response / lag
Symptoms: Process pressure changes quickly, but transmitter output changes slowly.
Possible causes:
Damping time set too high
Impulse line too long, too narrow, or partially blocked
Viscous media coating or scaling on diaphragm
Capillary-type remote seal inherently slower
Troubleshooting steps:
Check damping setting (via communicator).
Shorten impulse lines, increase diameter.
Clean diaphragm or replace with flush diaphragm seal.
Solutions:
Reduce damping (note: too little damping may cause output fluctuations).
Shorten impulse lines or switch to direct-mount transmitter.
For highly viscous media, use flush flange transmitter or switch to non-contact (radar).
Problem 7: Temperature-induced drift
Symptoms: Zero and span change with day/night or seasonal temperature variations.
Possible causes:
Transmitter lacks temperature compensation or compensation insufficient
Ambient temperature changes exceed specifications
Fill fluid expansion/contraction in remote seal capillaries
Troubleshooting steps:
Record zero readings at different temperatures to assess drift.
Check transmitter temperature coefficient specification against field conditions.
Solutions:
Use smart transmitter with full temperature compensation (e.g., Tiankang 3051 series, temp drift ≤0.005% FS/℃).
Provide thermal insulation for the transmitter.
For remote seals, select fill fluid with better thermal stability.
Use enclosure heating (avoid direct heat on transmitter).
Problem 8: Frequent failures in wet or corrosive environment
Symptoms: Transmitter repeatedly fails due to water ingress, terminal corrosion, PCB damage.
Possible causes:
Ingress protection (IP) rating insufficient for environment (e.g., IP65 in wash-down area)
Cable gland seal failed
Cover not tightened or seal aged
Troubleshooting steps:
Check IP rating on transmitter nameplate.
Open connection head and inspect for water or corrosion.
Solutions:
Replace with IP66/IP67 or IP68 transmitter.
Use Ex d or Ex e cable glands and install correctly.
Periodically inspect seals and apply sealing grease.
In extreme environments (offshore), choose stainless steel housing.
3. Preventive Maintenance Recommendations
In addition to troubleshooting after failure, regular maintenance greatly reduces pressure measurement problems:
| Task | Frequency | Description |
|---|---|---|
| Zero check | 3–6 months | Vent to atmosphere; re-zero if needed |
| Impulse line blow-down | Monthly or per process | Drain condensate, purge dust |
| Seal check | Quarterly | Check cable gland, flange gasket for leaks |
| Visual inspection | Monthly | Housing corrosion, nameplate legible, connection head dry |
| Calibration verification | Annually | Full-span calibration using hand pump or calibrator |
4. Reliability Guarantee of Tiankang Pressure Transmitters
Anhui Tiankang’s TK1151 and 3051 series pressure/differential pressure transmitters are designed and manufactured to prevent common issues:
Full temperature compensation: Automatic compensation over -40℃~85℃, temp drift ≤0.005% FS/℃.
High overpressure capability: Unidirectional overload 2–3 times range, preventing accidental overpressure damage.
EMC robustness: Passes IEC61000-4-4 Class IV, suitable for harsh electrical environments with VFDs and motors.
Ingress protection: Standard IP65, optional IP66/IP67; stainless steel housing for corrosive environments.
Ex ia/Ex d certifications: Suitable for Zone 1/2 hazardous areas.
Field zero/span adjustment: No communicator needed for basic adjustments; quick troubleshooting.
Adjustable damping: 0–100 seconds, adaptable to pulsating media.
5. Conclusion
Most pressure measurement problems follow predictable patterns: fixed output, fluctuation, drift, slow response, environmental sensitivity. Through systematic troubleshooting (power → signal loop → impulse lines → transmitter → environmental interference), the vast majority of issues can be quickly pinpointed and resolved.
Anhui Tiankang (Group) Co., Ltd. not only provides high-quality pressure transmitters but also offers full life-cycle technical support. If you encounter pressure measurement problems in the field, feel free to contact us.
Contact Us
📧 Email: [email protected]
📱 WhatsApp / Zalo: +86 17856068126
🌐 Website: http://www.tiankang-global.com/
Yin Shuangjie – Tiankang Instrument Technical Support
