The calorimetric principle

Unlike other methods of operation the calorimetric principle of E-T-A flow monitoring systems, which relies upon heat dissipation measured between two sensors, can be used to monitor the rate of flow of almost all media capable of moving through a pipeline, irrespective of their electrical conductivity, density, viscosity and contamination, and within a wide range of temperatures and pressures.

For accuracy of operation, calorimetric flow monitoring systems must convert a specific flow rate into a consistently equivalent voltage. To meet this requirement,

E-T-A monitoring heads are equipped with two sensors, one of which is used as a temperature reference.

E-T-A monitoring heads are sophisticated high-precision sensors. Approximately parallel temperature response curves of the sensors are ensured by keeping the thermal contact resistances as small and constant as possible: the more parallel the temperature curves of the two sensors, the lower the temperature drift.

Two alternative calorimetric methods are employed in E-T-A designs:

CP (Constant Power) method: Type SW and FS

The calorific power of the body is kept constant. The volume flow is determined by measuring the temperature difference between the two sensors. All E-T-A Flow Monitors are based on this method.

CTD (Constant Temperature Difference) method: Type FM

The temperature difference between the two sensors is kept constant. The volume flow is determined by measuring the calorific power. The calorimetric monitoring heads of the E-T-A Flow Meter FM 1 models are based on this method.