CS120A Power Supply Enclosure
4
Fig. 2. Mains Connections
The earth terminal acts as the main protective earth input for the enclosure. This
will be connected to the chassis plate and also to an earth boss on the base of the
enclosure which is identified as a protective earth.
If local regulations allow and/or require, the earth boss can be connected to an
earth external to the enclosure either to provide a better external earth for transient
protection or to ensure all local earths are bonded together, e.g. the earthing point
of a tower.
The enclosure will often be fitted with a secondary block of terminals labelled 24V
DC and 12 V DC (Fig. 3). The 24V DC from the AC fed power supply is the
output used to power the hood heaters of the CS120A. The 24V supply is often
also used to provide charging power to a backup power supply for the
microprocessor (DSP) of the CS120A, such as a PS100 or PS200 which may be
installed in the enclosure. That supply may also be used to power a datalogger or
other peripherals.
Where a backup supply has not been ordered a 12 V output will not be present and
both the heaters and DSP should be fed from the 24 V DC outputs.
Where a PS100 or PS200 is used as battery backup for the DSP electronics it will
be able to run the sensor for over 30 hours in the event of mains power failure.
The hood heaters will not be powered though.
