13 Important Factors Affecting Flow Meter Readings and Their Solutions

1. Fluid Characteristics

The physical properties of a fluid such as viscosity, density, and temperature  greatly affect flow meter performance. For example, a Coriolis flow meter measures mass flow directly and can automatically compensate for density changes, while a turbine flow meter is more sensitive to viscosity variations.
Even small temperature changes can alter the density of liquids or gases, leading to unstable readings.

Learn more about fluid properties and flow measurement from Emerson.

Solution: Use flow meters with built-in density or viscosity compensation features, and perform regular calibration when fluid properties vary with process conditions.

2. Air Bubbles or Gas Entrapment

Entrained air or gas bubbles are a common cause of fluctuating flow readings, especially in liquid systems. Air pockets interfere with sensors, creating false flow variations or signal spikes.

Solution: Install air eliminators, degassing chambers, or ensure the line is properly vented before the meter.

Refer: Krohne – Avoiding Air Bubbles in Flow Measurement

3. Pipe Vibration

Mechanical vibration from nearby pumps, compressors, or rotating equipment can disturb the flow profile and the meter’s sensing elements. Vibration especially affects differential pressure (DP) and ultrasonic flow meters.

Solution: Isolate the meter using vibration-damping supports or mount it on a section of the pipe that’s free from mechanical resonance.

See also: Siemens Flow Measurement Installation Tips

4. Pulsating Flow

Certain pumps particularly piston or diaphragm pumps create a pulsating rather than smooth flow. This pulsation leads to rapid pressure and velocity changes that the meter interprets as unstable flow.

Solution: Install a flow conditioner or pulse dampener upstream to stabilize the fluid before it reaches the meter.

5. Improper Installation

Incorrect installation is among the most frequent causes of flow meter instability. Mounting too close to pipe bends, valves, or pumps disturbs the flow profile, creating turbulence.

Solution: Follow the manufacturer’s installation guidelines and maintain sufficient straight pipe lengths (typically 10× upstream and 5× downstream of the meter diameter).

Reference: ISA – Flow Meter Installation Best Practices

6. Temperature Fluctuations

Sudden temperature variations can alter both fluid density and the internal resistance of the meter’s sensing components. These thermal effects often cause short-term instability. Temperature changes, pipe vibration, and air bubbles are some of the major factors affecting flow meter readings in industrial applications.

Solution: Choose a flow meter with temperature compensation or maintain a stable thermal environment around the process.

7. Electrical Interference

Nearby electrical equipment, variable frequency drives (VFDs), or high-current devices can introduce electromagnetic interference (EMI) into signal cables. This noise may corrupt the flow signal, especially in analog transmitters.

Solution: Use shielded cables, ensure proper grounding, and isolate power supplies where possible.

For more info, see NI – Mitigating Electrical Noise in Measurement Systems.

8. Wear and Tear

Flow meters contain moving or sensing components that gradually wear out with time, especially in abrasive or corrosive environments. Erosion, bearing damage, or sensor drift can lead to unstable or inaccurate readings.

Solution: Schedule periodic inspection and maintenance, and replace worn components as recommended by the manufacturer.

9. Calibration Issues

Even the best instruments lose accuracy without proper calibration. Incorrectly calibrated flow meters can show erratic readings that vary from the true value.

Solution: Follow a routine calibration schedule as per manufacturer or industry standards (such as ISO or API). Calibration should be done using a traceable reference standard.

Learn about flow meter calibration procedures on the International Society of Automation (ISA) website.

10. Pressure Fluctuations

Line pressure changes directly influence many types of flow meters, particularly differential pressure and variable area meters. Pressure surges can momentarily distort readings or even damage sensitive elements.

Solution: Stabilize system pressure using control valves, pressure dampers, or flow meters equipped with pressure-compensating sensors.

11. Blockages and Fouling

Over time, deposits, rust, or scaling can partially block pipes or meter internals, causing uneven flow distribution. This leads to unpredictable readings and poor repeatability.

Solution: Regularly clean and flush the flow meter and piping system. Consider using meters with self-cleaning designs or non-contact technologies like ultrasonic or magnetic flow meters.

12. Software and Configuration Errors

Modern digital flow meters depend on internal firmware and signal processing. Software glitches, incorrect configuration, or outdated firmware can cause output instability.

Solution: Keep firmware updated, back up configuration files, and periodically verify software settings.

13. Human and Instrumentation Errors

Sometimes instability results from manual interference, such as tampering with settings or faulty wiring. A loose terminal, broken signal cable, or malfunctioning transmitter can mimic unstable flow.

Solution: Perform a systematic diagnostic check verify wiring integrity, confirm correct signal scaling, and ensure proper integration with control systems.