Campbell Scientific PWS100 Present Weather Sensor - Manual (Page 121)

Appendix C. Cable Selection
C.2 Communication Cable
The PWS100 has RS-232, RS-422 and RS-485 communications capability.
Use a screened 2 × 0.22 mm
2 twisted pair cable. Maximum length is 15 m for
RS-232, 300 m for RS-422 and 300 m for RS-485.
The PWS100 is provided pre-wired with a default 10 m communications cable
as shown in Figure C-3 (other lengths available on request) which is terminated
at one end with a 9 pin D-connector (DB9). The D-connector can be connected
directly to a PC or datalogger such as the Campbell Scientific CR1000. If
another type of connection is required then the D-connector should be
removed. The other end is fed through the cable gland on the base of the
PWS100 DSP enclosure and fixed in the DSP terminal strip as shown in Figure
C-4. The cable connections for RS-232 and RS-485 are shown in Table C-1.
If another cable is to replace the pre-wired cable then ensure that the correct
cable is used and the wiring color scheme shown in Figures C-3 and C-4 is
followed exactly.
To remove the existing cable, unscrew the cable gland until the cable is loose
then locate the individual termination points of the wires. Using a small flat
blade screwdriver, press down the tab on the top of the terminal strip at the
point of the wire connection and pull the wire from the front slot. Carry this out
for all of the wires in the cable and then pull the cable from the cable gland
until free. Insert the new (stripped) cable and insert the wires into the
corresponding positions one by one by again depressing the tab on top of the
terminal strip and then securely pushing the stripped end of the wire fully into
the front slot.
TABLE C-1. Communication cable connections.
Color RS-232 RS-485
Blue TX Z
Green RX A
Black G G
White RTS B
Yellow CTS Y
Red Not Connected RS485G
Screen G G
In RS-232 mode the PWS100 supports hardware handshaking to
prevent data loss when sending data through slower devices, e.g.
modems. If the connected device does not support hardware
handshaking, to allow the PWS100 to transmit data do not
connect the RTS and CTS lines from the PWS100 but connect
them together to form a loop-back to the PWS100. NOTE
C-3