Instructions for Use
– SCHMIDT
®
Flow Sensor SS 20.700
Page 30
Error image
Possible causes
Troubleshooting
Problems with supply voltage
U
B
:
No U
B
present
U
B
has wrong polarity
U
B
< 15 V
Sensor defective
Is cable connector
screwed on correctly?
Is supply voltage con-
nected to the control?
Is voltage at the sensor
plug (cable break)?
Is power supply unit large
enough?
No LED is lit
All signal outputs at zero
Start sequence is repeated
continuously (all LEDs red -
yellow - green)
U
B
unstable:
Power supply unit unable
to supply switch-on current
Other consumers overload
U
B
Cable resistance too high
Is supply voltage at sen-
sor stable?
Is power supply unit large
enough?
Are voltage losses over
cable negligible?
Sensor element defective
Return sensor for repair
Supply voltage too low
Increase supply voltage
Supply voltage too high
Reduce supply voltage
Electronic temperature too
low
Increase temperature of
environment
Electronic temperature too
high
Lower temperature of
environment
Medium temperature too low
Increase medium
temperature
Medium temperature too high Lower medium temperature
Flow signal w
N
is too large /
small
Measuring range too small /
large
I-mode instead of U-mode
or vice versa
Medium to be measured does
not correspond to adjustment
medium
Sensor element soiled
Check sensor configuration
Check type or measuring
resistance
Is foreign gas correction
considered?
Clean sensor head
Flow signal w
N
is fluctuating U
B
unstable
Mounting conditions:
Sensor head is not in
optimum position
Inlet or outlet is too short
Strong fluctuations of
pressure or temperature
Check voltage supply
Check mounting conditions
Check operating parameters
Analog signal voltage per-
manently at maximum
Load resistance of signal
output connected to +U
B
Connect load resistance to
AGND
Analog signal voltage per-
manently at zero
Error signaling
Short circuit against (A)GND
Eliminate errors
Eliminate short circuit
Table 10
