Working Principle of Thermal mass flow meter.

The gases flowing through the pipelines often have different properties caused by a change in process conditions.

Therefore different operating principles are required for their measurement. One flow measurement based on thermal principle heat transport inflow.

Inside the thermal flow meters, two temperature sensors mounted in to the measuring tube known as Pt-100 RTD s . One of the measure s the gas temperature as reference regardless of the flow velocity. the second temperature sensor is heated constantly by a electrical energy so that a pre defined temperature difference is maintained between the probes. For example 10 Degrees Centigrade.

When thee is no flow , the change in temperature difference does not change. AS soon as the flow begins, the heat is drawn by the flowing fluid of the heated temperature sensor. the heat values are carried off by the flow. the corresponding cooling effect is measured and compensated immediately by adding more heating current as result the target temperature difference is continuously maintained. the heating current require to maintain the temperature difference is proportional to the cooling effect. therefore is a direct measure of the mass flow in the pipe lines.

Greater the flow velocity, therefore the additional cooling of the heater sensor, greater heating current required.