3
PHYTOS 31
Table 1 Installation (continued)
Connecting
Select Location for Data Logger and Cable
Connect to Logger
Plug the sensor into the logger.
In ZENTRA Utility, select PHYTOS 31 for the appropriate port.
Use the data logger to make sure the sensor is reading properly.
Verify that these readings are within expected ranges.
Secure and protect Cables
NOTE: Improperly protected cables can lead to severed cables or disconnected sensors.
Cabling issues can be caused by many factors such as rodent damage, driving over sensor
cables, tripping over cables, not leaving enough cable slack during installation, or poor
sensor wiring connections.
Install cables in conduit or plastic cladding when near the ground to avoid
rodent damage.
Relieve strain on the connections and prevent loose cabling from being
inadvertently snagged by gathering and securing the cables between the
PHYTOS 31 and the data logger to the mounting mast in one or more places.
Tie excess vertical cable to the data logger mast to ensure cable weight does
not cause sensor to unplug.
2.2 CONNECTING
The PHYTOS 31 works seamlessly with METER data loggers. The sensor can also be used
with other data loggers, such as those from Campbell Scientific, Inc.
The PHYTOS 31 sensor requires excitation voltages in the range of 2.5 to 5.0 VDC and
outputs a single-ended DC voltage that is proportional to the amount of water on the
sensor surface.
PHYTOS 31 produces an output voltage that depends on the dielectric constant of the
medium surrounding the sensor and ranges between 10% to 50% of the excitation
voltage. Any data logger that can produce a 2.5- to 5.0-V excitation with approximately
10-ms duration and read a voltage-level signal with 12-bit or better resolution should be
compatible with the PHYTOS 31. The current requirement at 2.5 V is around 2 mA and the
requirement at 5 V is 7 to 8 mA.
NOTE: The pHYTOS 31 is intended only for use with data loggers and readout devices that can provide short excitation
pulses, leaving the sensor turned off most of the time. Continuous excitation not only wastes battery power, but may,
under certain circumstances, cause the sensor to exceed government-specified limits on electromagnetic emissions.
PHYTOS 31 sensors come with a 3.5-mm stereo plug connector (
) to facilitate easy
connection with METER loggers. PHYTOS 31 sensors may be ordered with stripped and
tinned wires to facilitate connecting to some third-party loggers (
).
