Burkert 8756, Operating Instructions Manual

Page: 58 / 88

Type 8756
Setting and operation
english 58
Fluid inlet Fluid outlet
Sensor
Control valve
Electronics
w
x
y
xd = w-x
xout
Fig. 29: Function diagram of the MFC with control valve
w set-point value of the mass flow rate
x measured value of the mass flow rate
y set-point position of the control valve
The sensor measures the mass flow rate and compares the
measured value x with the set-point value w. Then the product
calculates the set-point position value y of the actuator.
▪ If the actuator is a pump, then the set-point position value y de-
termines the speed of the pump. For example, if the setpoint
position value y is equal to 10%, then the speed of the pump is
10%.
▪ If the actuator is a control valve, then the set-point position
value y determines the opening of the control valve. For ex-
ample, if the set-point position value y is equal to 10%, then
the opening of the control valve is 10%.
The transmission means of the set-point value w and the meas-
ured value of the flow rate depends on the product.
Refer to chapter: Product variant büS /CANopen [
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58] .
Refer to chapter: Product variant Analogue [
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58] .
If the operating conditions have changed, then optimise the
closed-loop control parameters. Refer to chapter:
Optimise
the closed-loop control parameters (MFC) [
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59]
To change the operating mode, change the source for the set-
point values. Refer to chapter:
Choose the source that gives
the set-point value (MFC) [
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60]
8.7.1 Product variant büS /CANopen
If the product detects that the pipe is empty, then the product
cannot regulate.
If you have an MFC with pump, then fill the pipe as described in
the chapter:
Fill the pipe without damaging the pump (MFC with
pump) [
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52]
After applying the operating voltage, the product enters a short
initialisation phase and switches to the normal operating mode.
The normal operating mode of a product variant büS/CANopen is
the
Automatic operating mode. The set-point value is set via the
fieldbus.
8.7.2 Product variant Analogue
If the product detects that the pipe is empty, then the product
cannot regulate.