User Manual
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7. Maintenance
The 229 does not require maintenance after it is installed in the soil. The
datalogger, current excitation module, and multiplexer, if used, should be kept in a
weatherproof enclosure. Periodic replacement of the desiccant in the enclosure is
required to keep the electronics dry and free of corrosion.
8. Troubleshooting
Symptom Possible
Cause
Action
Temperature reading is off
scale (-6999 or NAN)
Thermocouple wire not
connected to correct
datalogger channel
Check program to see which differential input channel
229 should be connected to and verify that it has a
good connection to that channel
Break in thermocouple wire
Use ohm-meter to measure resistance between blue
and red wires. The reading in ohms should be
approximately the cable length in feet. An open
circuit indicates a break in the wire
Multiplexer not operating
properly
Make sure that multiplexer has 12V between 12V and
GND terminals.
Check for a good electrical connection on the wires
that connect RES and CLK to datalogger control ports.
Check for a good electrical connection on the wires
going from the common channels to the datalogger
and the current excitation module.
Check program to make sure that the control port
connected to RES is being set high and the control port
connected to CLK is being pulsed.
DeltaT reading close to
zero
Heater wire broken or not
properly connected
Check resistance between terminal screws for green
and black wires. It should read 34 - 40 ohms.
Current excitation module
not turning on
Check for 12V b12V and ground terminals
Check for good electrical connection on wire
connecting CTRL with datalogger control port
Check program to make sure that control port
connected to CTRL is being set high
Temperature decreases
during heating
Thermocouple wires
reversed
Make sure blue wire is on the high side of the
differential input channel and red is on the low side
Readings for first sensor on
multiplexer are all right,
but all others read zero
All readings are being
written to the same input
location (Edlog dataloggers)
Check program to make sure measurement instructions
in the multiplexer loop are indexed
(-- next to the input location number. Press F4 or C to
toggle the --)
