Description; Measuring Procedure; Calorimetric Measuring Procedure - Flow vision FC100 - CA User Manual

Flow Meter | FC100-CA

1 Description

Flow Meter FC100-CA is suitable for compressed-air and other gas flow measurements under
various pressure conditions. It operates on the calorimetric principle and is to be used together with
monitoring heads CSx-...
These quantities are made available to the user as analogue electrical signals, physically isolated, as
current or voltage output and may be monitored by means of a limit monitor.
As relay outputs or transistor outputs the digital signals enable the user to integrate the FC100-CA
into a control and monitoring system.
The transistor outputs enable the user to additionally process fault, status and volume pulse indi-
cations in the control system.
A RS232 interface enables communication with FC100-CA.

1 . 1 Measuring procedure

1 . 1 . 1 Calorimetric 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 energy supplied is a function of temperature difference ∆ϑ and mass flow.
Flow Meter FC100-CA operates on the CTD (Constant-Temperature-Difference) method:
The temperature difference ∆ϑ between the two sensors is kept constant and the mass flow is deter-
mined by measuring the calorific power.
Fig. 1 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 RM assumes the temperature of
the medium ϑ whilst heater resistor RH heats element RS to temperature ϑ
M
medium, the temperature differential ∆ϑ = ϑ
CTD control 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.
control loop
6
DESCRIPTION
- ϑ
is preselected as a reference variable by the
S M
RM
RS
RH
K
p
ϑ
S
K
p
-x
−
K
+
p
ϑ
M
m: mass flow
w: reference variable ( )
Δϑ
x : actual value ( - )
ϑ ϑ
S M
S
medium
m
K ,T
p n
xd y
w
y
xd: system deviation
y : control variable
I : heater current
H
. As a function of the
I
H
U
I
fig. 1