Campbell Scientific PWS100 Present Weather Sensor - Manual (Page 29)

Section 6. Installation
6.3.3 Connecting Cables
The sensor unit comes with the DSP control unit fixed to the sensor arm. All
cabling between the sensor heads and the DSP unit is premade. An SDI-12
sensor connection is fixed into the DSP terminal strip. The connection is
terminated with a LEMO socket on the lower face of the DSP housing. This is
primarily wired for the CS215-PWS but is also used with the PWC100
Calibrator. Power, communications and additional sensor connections are to
be routed through the cable glands on the lower face of the DSP housing to the
DSP terminal strip. As a factory default, a power cable and a communications
cable are pre-wired in the unit. The third cable gland will be sealed off by
default but can be used for further external sensor connections or a separate
power cable for the hood heaters (rather than sharing the main power cable).
There should be no need to alter any wiring within the DSP housing and the
housing cover should only be removed periodically to renew desiccant packs or
if any of the hardware switches need to be used. However if cable lengths are
to be changed then these will have to be rewired in the DSP housing. If the unit
remains sealed during operation, the packs should only need replacing once
every 6 months. Replace the desiccant pack in the holder and secure the cover.
6.3.4 Basic Wiring
The PWS100 wiring block is shown on the internal layout diagram in Figure
B-2. Connection points for power and communications are shown in the
diagram. There are two power inputs (one 24V for hood heater and one 12V
for the processor board) one communications connection and two SDI-12 ports
for peripheral connection. For RS-485 communications a 120 Ω termination
resistor may need to be placed across the RTS-B and RX-A connections at
either end of the cable, although this is normally not required for most
installations unless electronic noise interference is prevalent or cable runs are
very long.
A 1K LEMO socket (IP66 rated) is used for connection of a peripheral (often
the CS215-PWS temperature / relative humidity probe). The cable for any
peripheral to be connected to the LEMO socket should be terminated with the
appropriate 4 pin 1K series LEMO plug. Ensure when fitting the peripheral
plug into the socket that the red tabs are aligned.
The power and communications cables are routed through two of the three
cable glands on the base of the PWS100 DSP enclosure. If power and
communications cables are replaced refer to Appendix C.1 and C.2 for further
details.
Figure 6-5 shows the lower face of the DSP enclosure with the cable gland and
LEMO connector positions.
6-7