Delta-T HH2, User Manual

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8
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Introduction to the Moisture Meter Moisture Meter User Manual 4.0
How the Moisture Meter takes readings
Analogue sensors (SM200, ML1, ML2, ML2x, EQ2, PR2, PR1)
The Moisture Meter applies power to the sensor and measures the output signal
voltage returned.
It displays this directly, in mV, and/or converts into other units, depending on the type
of sensor and information available. (Equitensiometer results can only be displayed in
mV.)
The meter converts the mV reading into soil moisture units using a linearisation table
and soil-specific parameters.
Linearisation tables are pre-installed for sensors, and for Organic and Mineral soil
parameters.
For greatest accuracy you can enter your own soil type parameters - but these have
to be determined experimentally. This is outside the scope of this manual.
For mm Deficit you need to supply Field Capacity and Root Depth for each soil type
and crop.
The date and time is saved with each reading. Before saving readings you may enter
a unique Plot, Sample or Device identity (ID) label.
Digital Sensor (WET)
The Moisture Meter applies power to the sensor, receives readings as serial data,
processes these (as described in the WET sensor Application Note available from
Delta-T), and calculates bulk and pore conductivity, bulk permittivity and temperature
as required. Using installed soil calibrations the HH2 calculates water content. Given
the root depth and field capacity it can also calculate mm Deficit.
Sleep and Waking the Meter
To conserve the battery, the meter will “go to sleep” when it is not used for 1 minute.
The display will go blank and the meter will power down to reduce its power
consumption.
To make the HH2 sleep, press
Esc once to return to the banner "Delta-T Devices
Moisture Meter" then press Esc one more time to make it sleep.
The meter will “wake up” when Esc is pressed or when RS232 messages are
received from the PC or when the battery is reconnected.
Averaging
Press # to shows the previous average – and press # twice to update it with the
current reading. Averages are not stored – sorry. Write it down if you need it.
For details see Averaging on page 14.