Hydronix Hydro-Probe Configuration And Calibration Manual page 45

Sensor Diagnostics
Symptom: Near Constant Moisture Reading
1.4
Possible
explanation
Empty bin or sensor
uncovered
Material stuck in bin
Build-up of material
on sensor face
Incorrect input
calibration within
control system
Sensor in alarm
condition – 0mA on
4-20mA range
Interference from
mobile phones
Average/Hold switch
has not operated
No power to sensor
No sensor output at
control system
No sensor output at
junction box
Sensor has shut
down
Internal failure or
incorrect
configuration
Check
Sensor is covered by
material
Material is not stuck
above sensor
Signs of build-up
such as dried solid
deposit on ceramic
face
Control system input
range
Moisture content of
material by oven
drying
Use of mobile
phones close to
sensor
Apply signal to digital
input
DC power at junction
box
Measure sensor
output current at
control system
Measure sensor
output current at
terminals in junction
box
Disconnect power for
30 seconds and retry
or measure current
drawn from power
supply
Remove sensor,
clean face & check
reading (a) with
ceramic face clean
and (b) with hand
pressed firmly on
ceramic face.
Required result
100mm minimum
depth of material
Smooth flow of
material over the
sensor face when the
gate is open
Ceramic faceplate
should be kept clean
by the action of
material flow
Control system
accepts output range
of sensor
Must be within
working range of
sensor
No RF sources
operating near to
sensor
Average moisture
reading should
change
+15Vdc to +30Vdc
Varies with moisture
content
Varies with moisture
content
Normal operation is
70mA – 150 mA
Reading should
change over a
reasonable range
Configuration and Calibration Guide HD0679 Rev 1.2.0 45
Chapter 5
Action required on
failure
Fill the bin
Look for causes of
erratic flow.
Reposition sensor if
problem continues
Check angle of the
ceramic in range of
30° to 60°. If problem
continues reposition
sensor.
Modify control
system, or
reconfigure sensor
Adjust sensor range
and/or calibration
Prevent use within
5m of sensor
Verify with Hydro-
Com diagnostics
Locate fault in power
supply/ wiring
Check cabling back
to junction box
Check sensor output
configuration
Check operating
temperature is within
specified range
Verify operation with
Hydro-Com
diagnostics