Chapter 7 Sensor Diagnostics; Symptom: No Output From Sensor; Sensor Output Characteristics - Hydronix Hydro-Probe SE User Manual

Chapter 7
The following tables list the most common faults found when using the sensor. If you are unable to
diagnose the problem from this information, please contact Hydronix technical support.
support@hydronix.com

1 Symptom: No output from sensor

Possible explanation Check
Sensor has
temporarily locked up
No power to sensor
No sensor output at
control system
No sensor output at
junction box
Sensor MIL-Spec
connector pins are
damaged
Internal failure or
incorrect configuration

2 Sensor output characteristics

A simple test can be performed to check the output from the sensor in air and with the hand.
Sensor exposed
to air
Hand on sensor
Power down and re-
power sensor
DC power at junction
box
Measure sensor
output current at
control system
Measure sensor
output current at
terminals in junction
box
Disconnect the sensor
cable and check if any
pins are damaged
Connect the sensor to
a PC using the Hydro-
Com software and a
suitable RS485
converter
(values shown are approximate)
RS485 4-20mA
0 4 mA
75-85 15-17 mA 16-18 mA
Table 1: Output test values
Sensor diagnostics
Required result
Sensor functions
correctly
+15Vdc to +30Vdc
Milliamp reading within
the normal range (0-
20mA, 4-20mA). Varies
with moisture content
Milliamp reading within
the normal range (0-
20mA, 4-20mA). Varies
with moisture content
Pins are bent and can
be bent to normal to
make electrical contact
Digital RS485
connection is working
Filtered Unscaled Output
0-20 mA 0-10 V
0 mA 0V
7.5-8.5 V
Hydro-Probe SE User Guide HD0278 Rev 2.1.0 47
Action required
on failure
Check power
Locate fault in
power
supply/wiring
Check cabling
back to junction
box
Check sensor
connector pins
Check sensor
configuration by
connecting to a
PC
Digital RS485
connection is not
working. Sensor
should be
returned to
Hydronix for
repair
Compatibility mode
>10V
3.6-2.8V