Pressure transmitters are widely used in industrial process control systems to measure pressure, differential pressure, and level. In real field applications, incorrect readings, unstable signals, or complete signal failure are common issues.
These problems are often not caused by the transmitter itself, but by installation, wiring, process conditions, or maintenance practices.
This guide summarizes the most common pressure transmitter failures and provides practical troubleshooting methods based on real industrial experience.
1. Pressure Transmitter Has No Output (0 mA / No Signal)
Possible Causes
A “no output” condition means the current loop is not working properly. Common causes include:
- Incorrect power supply wiring (reverse polarity)
- No 24V DC power supply in the loop
- Broken loop wiring or loose connection
- Display head (LCD module) damage
- Incorrect load resistance in the loop
Troubleshooting Steps
- Check whether the power polarity is correct
- Measure loop voltage (must be ≥ 12V DC at transmitter terminals)
- Verify 24V DC power supply is stable
- Short the display terminals (if equipped) to check if the indicator is faulty
- Insert a multimeter in series to measure loop current
- Check cable continuity and terminal connections
Solution
- Correct wiring polarity
- Ensure stable 24V DC power supply
- Replace damaged display module if necessary
- Repair broken loop wiring
- Ensure loop load resistance is within specification (typically ≤ 250Ω)
2. Output Current is Higher Than 20 mA
Possible Causes
An output above 20 mA usually indicates abnormal process conditions or electrical issues:
- Process pressure exceeds measuring range
- Sensor overload or diaphragm damage
- Incorrect range configuration
- Wiring short circuit or loose terminals
Troubleshooting Steps
- Verify actual process pressure value
- Check transmitter range setting
- Inspect wiring connections
- Measure loop voltage and load resistance
Solution
- Select a suitable pressure range
- Replace damaged sensor if overpressure occurred
- Rewire and tighten terminals
- Ensure loop resistance meets requirement:
RL ≤ (Supply Voltage – 12V) / 0.02A
3. Output Current is Lower Than 4 mA
Possible Causes
A low output signal indicates under-range or system failure:
- Pressure below lower range limit
- Sensor damage or failure
- Loop power supply instability
- Severe overrange damage in the past
Solution
- Confirm process pressure is within range
- Replace transmitter if sensor is damaged
- Stabilize power supply
- Recalibrate instrument if necessary
4. Incorrect Pressure Reading / Unstable Indication
Possible Causes
This is one of the most common field issues and may be caused by multiple factors:
- Incorrect calibration or range mismatch
- Electromagnetic interference (EMI)
- Poor grounding or shielding
- Blocked impulse lines or process piping
- Excessive temperature affecting sensor stability
- Installation position errors (height difference, condensation effects)
Troubleshooting Checklist
- Confirm reference pressure is accurate
- Ensure transmitter range matches display instrument
- Verify correct 4–20mA input configuration
- Check shielding and grounding system
- Inspect impulse lines for blockage or contamination
- Verify ambient and process temperature within limits
Solution
- Recalibrate transmitter and field instruments
- Clean impulse lines and install filters if necessary
- Improve grounding and cable shielding
- Separate signal cables from power lines
- Install condensate pots or cooling elements for steam applications
5. Installation-Related Problems (Very Common in the Field)
Incorrect installation is one of the leading causes of measurement errors.
Typical Issues
- Condensate level imbalance in steam applications
- Improper mounting height relative to process line
- Short impulse line length
- Improper drainage or slope in tubing systems
Impact
- Fluctuating readings
- Zero drift after restart
- Slow response or measurement lag
Recommendation
- Ensure correct impulse line routing
- Maintain proper slope for condensate drainage
- Keep transmitter installation stable and vibration-free
- Follow standard installation practices for steam and gas applications
6. Impulse Line Blockage
Cause
Over time, impurities, dust, or deposits may accumulate inside impulse lines.
Symptoms
- Pressure reading does not change with process condition
- Opening drain shows little or no discharge
Solution
- Clean impulse lines regularly
- Install filtration or flushing points
- Use proper flushing procedures during maintenance
7. Electrical Noise and Signal Interference
Cause
Electromagnetic interference is common in industrial environments such as:
- High-voltage power cables nearby
- Variable frequency drives (VFDs)
- Poor grounding system design
Symptoms
- Unstable or fluctuating output signal
- Random spikes in measurement data
Solution
- Use shielded cables
- Separate signal and power wiring
- Improve grounding system
- Avoid running signal cables through high-interference areas
8. Instrument Internal Failure
Even high-quality transmitters may degrade over time due to:
- Long-term operation in harsh environments
- Diaphragm fatigue
- Electronics aging
Symptoms
- Sudden signal loss
- Erratic output behavior
- Failure after years of stable operation
Solution
- Replace or repair transmitter
- Perform periodic calibration and preventive maintenance
- Select suitable model based on process conditions
Conclusion
Pressure transmitter faults are often not caused by instrument quality, but by installation, wiring, process conditions, or maintenance issues.
A systematic troubleshooting approach based on the 4–20mA signal loop can quickly identify most field problems:
- Check power supply first
- Verify loop current
- Inspect wiring and load resistance
- Evaluate process conditions
- Finally check instrument health
About Zero Instrument
Zero Instrument provides industrial pressure transmitters, differential pressure transmitters, flow meters, and level measurement solutions for global industrial applications, including oil & gas, water treatment, chemical, and power industries.