Burkert 8745 MFC Ethernet, Operating Instructions Manual

Page: 52 / 70

52
Setting and Operation
Type 8745 Ethernet, 8745 Analogue
10.7 Normal operating mode (MFC)
The normal operating mode is active when energizing the product
for the first time. Fig. 31 . shows the normal operating mode of an
MFC.
NOTICE
if the valve seat seal is made of a hard material such as
pcTfe, then the control valve may not be tight.
Products with a nominal valve diameter of 0.05 mm or 0.1 mm
have a valve seat seal made of a hard material.
w
x
out
y
x
x
d
= w-x
Electronics
Sensor
Control valve
Fluid inlet
Fluid outlet
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
Fig. 31: Function diagram of the MFC
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 control valve. The
set-point position value y determines the opening of the control
valve. For example, 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 measured
value of the flow rate depends on the product. Refer to chpt. 10.7.1
Product variant Ethernet or to chpt. 10.7.2 Product variant Analogue .
→
If the operating fluid is not the calibration fluid then run
the Autotune function. Refer to chpt. 10.8 Optimise the
closed-loop control parameters (MFC) .
→
If the pressure conditions have changed, then run the
Autotune function. Refer to chpt. 10.8 Optimise the
closed-loop control parameters (MFC) .
→
To change the operating mode, change the source for the set-
point values. Refer to chpt. 10.9 .
10.7.1 Product variant Ethernet
After applying the operating voltage, the product enters a short
initialisation phase and then switches to the normal operating mode.
The normal operating mode of a product variant Ethernet is the
automatic operating mode. The set-point value is set via the fieldbus.
10.7.2 Product variant Analogue
After applying the operating voltage, the product enters a short
initialisation phase and then switches to the normal operating mode.
The normal operating mode of a product variant Analogue is the
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