Campbell Scientific CS420 and CS425 PDCR 1830-8388 Pressure Transducer - Manual (Page 6)

CS420-L and CS425-L Pressure Transducers
3. Installation
3.1 Vent Tubes
A vent tube incorporated in the cable vents the sensor diaphragm to the
atmosphere. This eliminates the need to compensate the water level
measurement for changes in barometric pressure.
To prevent water vapor from entering the inner cavity of the sensor, the
transducers are typically shipped with the vent tubes sealed. Before operation,
visually confirm the vent tube is open. The vent tube opening must terminate
inside a desiccated enclosure or a Campbell Scientific DES2 desiccant case.
The desiccant must be changed regularly. NOTE
3.2 Dislodging Bubbles
While submersing the sensor, air bubbles may become trapped between the
pressure plate and the water surface, causing small offset errors until the
bubbles dissolve. Dislodge these bubbles by gently shaking the pressure
transducer while it is under water.
Do not hit the sensor against the well casing or other solid
surface while dislodging the bubbles, because the
diaphragm could be damaged. CAUTION
3.3 Transient Protection
Campbell Scientific recommends transient surge protection for sensors
installed in lightning prone areas. No lightning protection is capable of
withstanding a direct hit, but surge protectors afford a degree of protection for
near misses. Surge protection can be provided by Campbell Scientific’s
SVP48 Surge Voltage Protector. When an electrical surge occurs, the surge
protectors involved may need to be replaced.
3.4 Temperature Fluctuations
Temperature fluctuations can be minimized by using a minimum cable burial
depth of six inches and a sensor submersion depth of one foot. Also, if your
site may experience extreme temperature fluctuations, the transducer must be
measured using the six-wire configuration.
4. Datalogger - Sensor Connections
The transducers are configured for a six-wire measurement. If using short
cable lengths (< 100 feet) and extreme temperature fluctuations are not likely,
a four-wire measurement can also be made reliably. The six-wire
measurement is more accurate and the only advantage of the four-wire
measurement is it requires fewer analog channels. The four-wire configuration
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