Hydronix Hydro-Probe XT User Manual page 55

Sensor diagnostics
Symptom: Near constant moisture reading
1.4
Possible
explanation
Empty bin or sensor
uncovered
Material 'hanging up'
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 hanging
up 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 +15Vdc to
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 open
and (b) with hand
pressed firmly on
ceramic face. Activate
Average /Hold input if
required
Required result Action required on
failure
100mm minimum Fill the bin
depth of material
A smooth flow of Look for causes of
material over the erratic flow of
face of the sensor material. Reposition
when the gate is sensor if problem
open continues
Ceramic faceplate Check angle of the
should be kept ceramic in range of
clean by the 30° to 60°.
action of material Reposition sensor if
flow problem continues
Control system Modify control
accepts output system, or
range of sensor reconfigure sensor
Must be within Adjust sensor range
working range of and/or calibration
sensor
No RF sources Prevent use within
operating near to 5m of sensor
sensor
Average moisture Verify with Hydro-
reading should Com diagnostics
change
Locate fault in power
+30Vdc supply/ wiring
Varies with Check cabling back
moisture content to junction box
Varies with Check sensor output
moisture content configuration
Normal operation Check operating
is 70mA – 150 temperature is within
mA specified range
Reading should Verify operation with
change over a Hydro-Com
reasonable range diagnostics
Hydro-Probe XT User Guide HD0538 Rev: 1.6.0 55
Chapter 7