!
Flow control should be set to none.
In addition, these setting will make the program easier to use. In Hyper Terminal these settings
are found under
File / Properties / Settings / ASCII Setup / ACSII Sending
:
!
Check “
Send line ends with line feeds
”. All commands sent to an RS-485
version of the Hydra Probe must end with a “Carriage Return” “Line Feed” pair.
!
Check “
Echo typed characters locally
”. The Hydra Probe does not echo any
commands. Checking this enables you to see what you have typed.
2.2 Analog Hydra Probe
The Analog Hydra Probe was the first version made available. The Analog version is useful for a
number of applications. Current customers of the Analog probe include users that need to replace
or add a sensor to an existing system that was specifically tailored for the analog sensors. One
advantage the Analog Hydra Probe has over the digital version is the fast measurement rate. For
example, on the beach, ocean researchers can use the analog Hydra Probe to measure the
hydrology of sands in the surf zone where they would want to take several measurements
between waves. This would entail taking measurements several times per second, something the
digital probes cannot do.
2.2.1 Analog Hydra Probe Output
The output of the Analog Hydra Probe is 4 voltages. These four voltages are the raw signal
response of the measurement and directly represent the behavior of the reflected electromagnetic
standing wave. The four voltages need to be processed by a computer program in order to obtain
the parameters of interest such as soil temperature, soil moisture, soil electrical conductivity and
the dielectric constants.
Table 2.4 below shows the wiring scheme.
Black Wire
Ground
Red Wire
Power 7 to 30 VDC (12 VDC Ideal)
Blue Wire (Output)
V1 (Raw Voltage 1) Range 0-2.5 volts
Brown Wire (Output)
V2 (Raw Voltage 2) Range 0-2.5 volts
Green Wire (Output)
V3 (Raw Voltage 3) Range 0-2.5 volts
White Wire (Output)
V4 (Raw Voltage 4) Range 0-1 volts
Yellow Wire
Reference Ground
Power Draw Active
35 to 40 mA
Table 2.4 wiring scheme for the Analog Hydra Probe.
An easy way to remember the wiring scheme is the colors of the wires are ordered
alphabetically. The black and yellow ground wires may be connected and grounded together or
grounded separately. The four voltage data wires need to be wired into four separate voltage
sensing connection points on the recording instrument. On the Stevens DOT Logger, the analog
ports are labeled A1, A2, A3, and A4. Use the logger data acquisition procedure to obtain the
raw voltages values. For more information about the Stevens Dot Logger, see appendix C.
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