Technical data

ManualsBrandsETA Systems ManualsOxygen EquipmentFC01-LQ

Flow meter FC01-Ex Flow meter FC01-Ex

Normal atmosphere - Definitions and mounting instructions 19 Normal atmosphere - Definitions and mounting instructions 19

3 Normal atmosphere - Definitions and mounting instructions

3.1 Measuring procedure

The calorimetric measuring procedure is based on the physics of heat dissipation, i.e. a body with

a temperature higher than its surroundings supplies a medium flowing past that body with energy

in the form of heat. The amount of energy supplied is a function of temperature difference Δϑ and

mass flow.

Flow Meter FC01-Ex operates on the CTD (Constant Temperature Differential) method:

The temperature difference  between the two sensors is kept constant and the mass flow is

determined by measuring the calorific power.

Fig. 12 is a schematic diagram of a CTD method based sensor. Two temperature-sensitive resistors

(sensor elements RS and RM) are immersed in the medium. Sensor element RM assumes the

temperature 

of the medium whilst heater resistor RH heats element RS to temperature 

. As a

function of the medium, the temperature differential  = 

- 

is preselected as a reference

variable by the CTD control with ∏ characteristics and is kept constant. The required calorific

power is a function of mass flow so that the control variable y of the control can be used for

evaluation.

Major benefits of this method are:

● Fast response, particularly to sudden flow standstill.

● Medium temperature measurement, providing optimum temperature compensation.

● Increased safety because the sensor cannot be overheated during the standstill.

The flow rate is determined by mass flow.