IFM SU2020, Operating Instructions Manual

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Ultrasonic flow meter SU2020 SU8020 SU2021 SU8021 SU2621 SU8621
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The switching output is switched on in normal operation (normally closed) and the switching status
LED lights yellow.
If the unit detects a diagnostic case, the output is switched off and the switching status LED goes out.
Diagnostic cases are:
• reversal of the flow direction (
Ò
Switching signal for flow direction
/
27)
• low signal quality / no signal (
Ò
Switching signal for signal quality
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27)
10.3.2.1 Switching signal for flow direction
A flow direction change can be monitored by providing a switching signal.
An arrow with the text “flow direction” on the unit indicates the positive flow direction. The direction of
the flow measurement can be reversed using the parameter [Fdir]. See
Flow direction (
Ò /
37) .
The output is switched on until the volumetric flow falls below the set minimum volumetric flow quantity
in negative flow direction (- LFC)(1).
Then the following applies:
• The output switches ON when volumetric flow is above + LFC (2).
• The output switches OFF when volumetric flow is below - LFC (3).
LFC = low flow cut-off: Low flow cut-off (
Ò /
37) .
2 3 1
+ LFC
+ Q
- Q
- LFC
1
0
Fig. 20: monitoring of the flow direction by switching signals
+Q volumetric flow in positive flow direction
-Q volumetric flow in negative flow direction
+LFC minimum volumetric flow (low flow cut-off) in positive flow direction
-LFC minimum volumetric flow (low flow cut-off) in negative flow direction
Parameter setting via unit keys: switching signal for flow direction
u
Go to the [EF] > [OUTx] menu.
u Select [oux] > [dOU] and set [Fdir].
Parameter setting via IO-Link: switching signal for flow direction
u
Call up [Parameters] > [Output Configuration].
u
Select [oux] and set [dOU].
u
Select [dFUx] and set [Flow direction].
10.3.2.2 Switching signal for signal quality
The unit can provide a switching signal when the signal quality deviates from normal operation.
The signal quality of the sensor can be affected by irregularities in the medium (e.g. strong
turbulences, air bubbles, particles or build-up).
The unit detects the signal quality in three stages: