Instructions for Use
– SCHMIDT
®
Flow sensor SS 20.260
Page 15
7 Information concerning operation
Soiling or other gratings on the sensor cause distortions of meas-
urements.
Therefore, the sensor must be checked for soiling at regular in-
tervals and cleaned if necessary.
(Condensing) liquid on the sensor causes serious measurement
distortions.
After drying the correct measuring function is restored.
Eliminating malfunctions
The following Table 6 lists possible errors (error images). A description of
the way to detect errors is given. Furthermore, the possible causes and
measures to be taken to eliminate errors are listed.
Error image
Possible causes
Troubleshooting
Problems with supply voltage U
B
:
No U
B
available
U
B
has wrong polarity
U
B
< approx. 6.5 V
Sensor defective
Sensor cable connected cor-
rectly?
Supply voltage connected to
control?
Supply cable broken?
Power supply unit large
enough?
I
wN
, I
TM
= 0 mA
Sensor element defective
Send in sensor for repair
I
wN
, I
TM
= 2 mA
Operating voltage beyond specifi-
cation range (too low / high)
Medium temperature beyond spec-
ification range (too low / high)
Check operating voltage and set
it correctly
Check medium temperature and
set it correctly
I
wN
, I
TM
= 2 mA
Flow signal w
N
is
too large / small
Measuring range too small /large
Medium is not air
Sensor element soiled
Sensor installed in opposite direc-
tion to flow direction
Check sensor configuration
Check measuring resistance
Is foreign gas factor correct?
Clean sensor tip
Check installation direction
Flow signal w
N
is
fluctuating
U
B
unstable
Mounting conditions:
Sensor head is not in optimal
position
Run-in/run-out distance is too
short
Strong fluctuations of pressure or
temperature
Check voltage supply
Check mounting conditions
Check operating parameters
Table 6
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