Overview – Campbell Scientific 227-L Delmhorst Cylindrical Soil Moisture Block User Manual
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227 Delmhorst Cylindrical Soil Moisture Block
9. Click
on
Wiring Diagram and wire the 227 to the CR1000 according to
the wiring diagram generated by SCWin Short Cut.
5. Overview
The 227 gypsum soil moisture block connects directly with a Campbell
Scientific datalogger; it is not compatible with our CR200(X)-series.
The –L option on the Model 227-L indicates that the cable length is user
specified. This manual refers to the sensor as the 227. The cable can terminate
in:
• Pigtails that connect directly to a Campbell Scientific datalogger.
• Connector that attaches to a prewired enclosure (option –PW). Refer
to
r more information.
The Delmhorst cylindrical block is composed of gypsum cast around two
concentric electrodes which confine current flow to the interior of the block,
greatly reducing potential ground loops. Gypsum located between the outer
electrode and the soil creates a buffer against salts which may affect the
electrical conductivity. Individual calibrations are required for accurate
readings of soil water potential.
The 227 circuit has capacitors in the cable that block direct current flow from
the 227 to datalogger ground. This is done to block electrolysis from
prematurely destroying the sensor.
Gypsum blocks typically last for one to two years. Saline or acidic soils tend
to degrade the block, reducing longevity. To maximize longevity, it is
recommended that gypsum blocks not used during the winter be removed from
the field. Shallow blocks may become frozen and crack, while blocks located
below the frost line may not maintain full contact with the soil. Regardless of
depth, blocks left in the field over winter are subject to the corrosive chemistry
of the soil.
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