5
CONNECTING SENSORS
VP-4
digital input, the bare ground wire to ground as illustrated below.
Figure 7: Wiring Diagram
Note: The acceptable range of excitation voltages is from 3.6 to 15
VDC. If you wish to read the VP-4 with the Campbell Scientific Data
Loggers, you must power the sensors off a 12 V or switched 12 V port.
If your VP-4 has a standard 3.5 mm plug, and if you wish to connect
it to a non-Decagon data logger, you have two options. First, you
can clip off the plug on the sensor cable, strip and tin the wires,
and wire it directly into the data logger. This has the advantage of
creating a direct connection with no chance of the sensor becoming
unplugged; however, it then cannot be easily used in the future with
a Decagon readout unit or data logger. The other option is to obtain
an adapter cable from Decagon. The 3-wire sensor adapter cable has
a connector for the sensor jack on one end, and three wires on the
other end for connection to a data logger (this type of wire is often
referred to as a “pigtail adapter”). Both the stripped and tinned
adapter cable wires have the same termination as seen above; the
white wire is excitation, red is output, and the bare wire is ground.
14
