Getting Started
Page 8
7. Connect the white wire from the sensor and the other wire from the valve to the
common wire.
8. Connect the red wire from the senor to the zone wire that you disconnected from the
valve. Use DBY connectors to make these 3 connections.
Sensor Configuration
Once the valve wires are connected to the controller scan for hardware using the Off Add/
Remove Hardware feature (see page 16). The controller will locate the sensor
automatically and properly configure the system. The sensor is now wired into the system
and ready for use.
Sensor Thresholds
Soil acts much like a sponge. When you immerse a sponge in
water and repeatedly squeeze it, it becomes saturated. If you
remove it from the water it will drain rapidly then drip for a while.
Gravitational forces act against capillary forces until equilibrium is
reached and the sponge stops dripping. This equilibrium state is
called 'Field Capacity' (FC). There is still plenty of water in the
sponge but gravitational forces are not strong enough to pull it out.
When soil is at field capacity and slightly below conditions are
excellent for plants. The addition of water above field capacity
wastes water, causes leeching, and
depletes the soil of valuable nutrients, while also contaminating the groundwater with
pesticides and fertilizers. It also drives oxygen out of the soil and suffocates the roots.
As soil dries out from field capacity a point is reached where plants have difficulty
drawing water out of the soil and begin to experience stress. This lower limit to which you
can allow your plants to experience is called 'Management Allowable Depletion' (MAD).
This is the point where irrigation water must be applied to keep the plants from
experiencing stress. If water is not applied the soil will dry to the 'Permanent Wilt
Point' (PWP). This is the point at which the plant dies.
The proper moisture zone for healthy plants is between Field Capacity and Management
Allowable Depletion. Management Allowable Depletion is typically 75% of Field Capacity
in absolute volumetric water content terms. The Acclima sensor measures absolute
volumetric water content. Field Capacity can easily be determined by flooding the sensor
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