Flow vision FC 01- CA, User Manual

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Flow Meter | FC 01- CA
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DESCRIPTION
1 Description
Flow Meter FC01-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 CS_...
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 FC01-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.
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 FC01-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
determined 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
M
whilst heater resistor RH heats element RS to temperature
ϑ
S
. As a function of the
medium, the temperature differential
∆ϑ
=
ϑ
S
-
ϑ
M
is preselected as a reference variable by the
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.
RM
RS
RH
m
K
p
K
p
S
M
K
p
−
+
-x xd
w
y
K
p
,T
n
U
I
I
H
y
m: mass flow
w: reference variable (
)
x : actual value (
S
-
M
)
xd: system deviation
y : control variable
I
H
: heater current
control loop
medium
Δϑ
ϑ
ϑ
ϑ ϑ
fig. 1