1. The recorder sends out the verify command:
aV!
2. Upon receiving the verify command the sensor will respond with:
a0016<CR><LF>
indicating that after 1 second the sensor will respond with 6 data items.
3. The sensor begins a self-diagnostic sequence in which the waveform is examined, the power
line voltage is measured and the temperature is measured. The sensor then sends out a
service request
.
a <CR><LF>
4. The recorder issues a
read data
command
D0
:
aD0!
5. The sensor responds with:
TestErSDIVSDI12Temp+LTAmMeasureErrCode
The Test Error Code Reports:
Bit 0
Incident wave begins above specified level
Bit 1
Incident wave does not rise to specified level
Bit 2
SDI12 voltage is out of spec when sensor is idle
Bit 3
SDI12 voltage is out of spec when sensor is operating
Bit 4
Temperature reading is not reasonable
Bit 5
Soil Conductivity too high for sensor operation
The measure error code indicates that a point was reached in the waveform analysis where an
unresolvable mathematical condition was reached. This would be due to shorted rods or to
some internal sensor failure.
Retrieving the TDR Sensor Waveform:
The Acclima TDR sensors were developed as Time Domain soil permittivity and moisture content
measuring devices but have application in many other research disciplines. TDR waveforms contain
much more data than soil moisture content. Soil electrical conductivity can be determined from them. Also
other properties of the soil such as porosity and particle size have an influence on the characteristics of
the waveform
– hence it is appropriate for some researchers to use TDR waveforms in characterizing
these additional properties. The spectral content of the Acclima TDR waveforms is well preserved since
there is no low pass filter (coaxial cable) between the waveguide and the digitizer. These factors provide
an opportunity for additional time domain and frequency domain analyses of the waveform that can yield
