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5
EQ2-UM-1.3
Connections
Cable Connections
The
Equitensiometer
is supplied with a four core, screened cable which provides these
connections:
Red
Power V+
Blue
Power 0V
Yellow
Signal HI, (load resistance 10K
Ω
minimum)
Green
Signal LO
Braid
Cable screen. Not connected within probe.
The Blue and Green leads are connected internally.
The braid screen should be connected to digital ground on the logger or other measuring
unit. If not using Delta-T equipment, please refer to the manufacturer's instructions.
If you simply want to log the probe voltage directly, it can be treated as a differential
voltage source of range 0 - 1.5V DC, and the attached meter or logger should be configured
accordingly.
Warning: use as a single-ended voltage source will introduce measurement errors due
to the sensor power return current and is not recommended.
Some
Equitensiometer
variants have a connector fitted in order to mate to the appropriate
Delta-T instrumentation. Connection details are given in the relevant instrumentation User
Manual.
Electromagnetic Compatibility ( EMC )
The
Equitensiometer
has been assessed for compatibility under the European Union EMC
Directive 89/336/EEC and conforms to the appropriate standards, provided the moisture
measuring rods and probe body are completely immersed in the soil or other material being
measured. The cable connecting the
Equitensiometer
to its associated instrumentation
should also be routed along the surface of the soil.
If the probe is not installed in this way, some interference may be experienced on nearby
radio equipment. Under most conditions, moving the equipment further from
Equitensiometer
(typically 1-2 metres) will stop the interference.
Equitensiometers
installed near to each other will not malfunction due to interference.
Power supply and warm-ups
The
Equitensiometer
requires a power supply of 5 to 15V DC at approximately 20mA. For
complete stability, a warm-up time of 5s is recommended, although good repeatability can
be achieved using a 1s warm-up.
Battery power consumed by a probe for a single measurement taken with a 5 second warm-
up time is typically: 20mA * 5s
≅
0.03mA.h
