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ENGINEERING NOTE
th
RELEASE DATE: 06
JUNE 2006
EDITION 1.6
CVS-001, Closed Venting System for Vented Sensors
SUBJECT:
INTRODUCTION
When pressure sensors are deployed, there can be a difference between the atmospheric temperature and the
temperature of the sensor at depth.
This temperature differential causes a pumping effect to occur whereby moist air from the surface is drawn into
the sensor through the vent line. This moisture can condense on sensitive electronic components due to warm
surface air cooling inside the sensor.
Sealing the system against exposure to the atmosphere and conditioning the existing air in the vent tube can
alleviate this problem. Silica desiccant crystals easily absorb moisture thereby drying the air and are used in the
closed loop venting system CVS-001.
The effectiveness of the closed venting method is compromised if the system is disassembled. Therefore, once
installed or reassembled, some time is required for trapped air to become dry again. One advantage of this
method is that the volume of air being dried is always constant therefore the desiccant crystal will not become
saturated.
INSTALLATION
Suggested Installation Only
The unit is fitted with a DIN clip for fitting to standard DIN rail installations. Sensor cable wires are terminated in
suitable DIN rail screw terminal blocks available from electrical suppliers. A vent tube joiner (supplied) is fitted
between the CVS-001 and the cable vent line. See Figure 1.
A single CVS-001 is designed to handle sensor cable lengths up to 70 metres. Multiple units may be joined
together for greater capacity. For example, if a 140 metre cable is used, two units connected via a 'T-Piece'
(available from Greenspan, Part, 071-9112) and extra joiner tubing (071-0008) are connected as per Figure 2.
Note that there are many ways of installing CVS-001, these are only suggestions.
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