Application Cautions for Thermal Flow Meters
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Application Cautions for Thermal Flow Meters Thermal flow meters should not be applied to abrasive fluids because they can damage the sensor. Fluids that coat the sensor can alter the relationship between the thermal properties of the fluid and the measurement and adversely affect the flow measurement. Extensive coating can render the sensor inoperable unless the sensor is routinely cleaned. This can increase maintenance associated with these flow meters. Varying the percentage of certain components that have different thermal properties from calibrated values can cause thermal flow meters to become highly inaccurate. In other words, thermal flow meters are often not suitable for applications with fluids that have varying composition and unknown components. However, in some applications, thermal flow meters could measure reasonably accurately when the flow stream contains components with similar thermal properties. Aerosols and gases with droplets can cause thermal flow meters to become erratic and/or measure full scale flow. This is because the large amount of thermal energy used to heat the liquid/droplet is interpreted as a high flow signal. Operating a thermal flow meter above its maximum flow rate will generally not damage the flow meter but can cause measurement error because its calibration curve can become unpredictable. |