EQ2-UM-1.3
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Connection and configuration for Delta-T loggers (DL2 & DL3000)
Equitensiometers
can be directly powered by Delta-T loggers using their internal batteries.
However, if several probes are to be used, or if the logger has to supply significant power
to other sensors or accessories, we recommend powering the logger and sensors from an
external power supply. Although the probe can be continuously powered, significant
power can be saved by using a warm-up relay to energise the sensor just before and during
a log.
The DL2e and DL3000 loggers include a minimum of two relay-controlled outputs to
provide and control sensor power. Each relay is capable of switching 1A, which means that
each logger can power 60
Equitensiometers
provided they are the sole warm-up relay
contact load.
DL2e connection and configuration
This diagram shows the connections
for an
Equitensiometer
connected to
channel 1 of a DL2e in differential
mode, and powered through the
loggers internal power supply.
Further details can be found in the
SENSORS.TXT
file, which is supplied
with the DL2e sensor codes for the
Equitensiometer
, and in the DL2e
user manual in the Relay Channels
section.
Two sensor configuration codes are
supplied with the DL2e:
E2D
is intended for linearising the full range of EQ2 output (0 to
-1000kPa), and
E2W
which provides more resolution at the wet end only (0 to -350kPa).
You will need to enter the individual linearisation table values attached to the calibration
data that is supplied with each of your
Equitensiometers
.
DL3000 connection and configuration
Full details, including example connection diagrams, are available in the online help
provided with Acquire!. The DL3000 can accept linearisation tables with unequal step
sizes, so you can enter the calibration table exactly as supplied, and the DL3000 will then
linearise to full resolution over the full range.
Note: each Equitensiometer needs its own linearisation table.
Operational considerations
Hysteresis and response time effects
The
Equitensiometer
only reads correctly once the equilibrium state within the probe is
reached. Normally there is a time lag between the change of matric potential of the
surrounding soil and the response of the
Equitensiometer
. This time lag is greatest when
the matric potential is changing fast, and at large (negative) matric potentials, see Table 1.
Under natural conditions, changes in matric potential are normally less than 0.01 kPa/min,
so the associated errors will therefore be much lower than the values in Table 1. As shown
