10 Troubleshooting
Sensor does not respond on the RS-485/SDI-12 interface
▶
For SDI-12 protocol: Sensor correctly connected to a data logger with SDI-12
input?
➝
Correct connection assignment.
▶
Polarity of the supply voltage reversed?
➝
Correct connection assignment.
▶
Supply voltage < 5.5 V or > 28.8 V?
➝
Adjust level of voltage supplied (check the length and cross-section of the
connection cable).
▶
Is the supply voltage not direct current?
➝
Only operate the sensor with direct current.
▶
Does the sensor address of the OTT PLS 500 correspond with the sensor
address used by the data logger?
➝
Correct sensor address.
Sensor does not respond on the RS-485 interface to …
▶
SDI-12 commands: is the RS-485 interface of the sensor configured to Modbus-
protocol?
➝
Test communication via Modbus communication.
▶
Modbus communication: is the RS-485 interface of the sensor configured to
SDI-12 protocol?
➝
Test communication via SDI-12 commands.
Sensor does not respond on the RS-485 interface
▶
"RS-485 A" and "RS-485 B" wires interchanged?
➝
Correct the wire assignment.
Measured value varies unexpectedly, jumps or is not present
▶
Sensor soiled
➝
Clean sensor carefully; see Chapter 9, "Carrying out maintenance work".
▶
Installation of the sensor steady (e.g. movement from swell)?
Control option: Perform system test of the OTT PLS 500 with
aV!
and retrieve
result with
aD0!
and
aD1!
(e.g. as described in Chapter 6). If
<value3>
deviates from
<value4>
by several degrees, this indicates a change in the
orientation of the probe.
➝
Optimise installation.
▶
Condensed water drop in the pressure compensation capillary?
Control option: Perform system test of the OTT PLS 500 with
aV!
and retrieve
result with
aD0!
(e.g. as described in Chapter 6). The
<value1>
shows the
relative humidity inside the probe. If this is greatly increased, it indicates that
moisture has penetrated the pressure compensation capillary. In most cases
this type of error is caused by a missing or insufficiently maintained humidity
absorber.
➝
Replace the pressure probe.
Various types of error
▶
Errors that cannot be narrowed down further occur; however, communication
on the RS-485-/SDI-12 interface via SDI-12 commands is possible
1)
:
➝
Perform a system test of the OTT PLS 500 with
aV!
and retrieve result with
aD0!
…
aD2!
. For interpretation of the responses, see Chapter 7.2,
aD0!
,
aD1!
and
aD2!
after
aV!
.
1)
for example, via interface converter "OTT USB/SDI-12 Adapter" in combination with the PC software
"OTT SDI-12 Interface"; see Chapter 6
48
