SC932A CS I/O to RS-232-DCE Interface
4
excellent immunity to circuit noise. TABLE
4-1
gives the data rate possible for
several gage cables across several distances.
TABLE 4-1. Approximate Range, miles and km
Data Rate 19 Gauge (0.9 mm) 24 Gauge (0.5 mm) 26 Gauge (0.4 mm)
bps
miles
km
miles
km
miles
km
9,600
6.2
10.0
2.8
4.5
2.0
3.3
1,200
7.6
12.2
3.4
5.5
2.5
4.0
4.1 RAD Modem – Two-Way
4-WIRE UNCONDITIONED
TELEPHONE LINE
OR
TWO TWISTED PAIRS
SRM
9 TO 25 PIN
ADAPTOR
SC932A DATALOGGER
PC SRM
FIGURE 4-1. Two-Way Communication
When using Campbell Scientific’s datalogger support software to communicate
through the SC932/RAD modem, set up the link as a direct connect between
the datalogger and the desired COM port. Start two-way communication using
the
Connect
button on the toolbar or the
Connect
button on the
Connect
window.
4.2 RAD Modem Wiring and Grounding
FIGURE
4-2
shows a typical setup of the RAD modems. Installation is as
follows:
1. Set the DCE/DTE switch on the back of the RAD modem connected to
the SC932A to DCE. For a RAD modem connected to a PC, set the
DCE/DTE switch to DCE. For a RAD modem connected to a serial
printer, set the DCE/DTE switch to DTE.
2. Select a cable with two or more twisted pairs. A recommended direct
burial rodent resistant cable is listed below. They also sell several gopher
resistant cables for even greater protection.
Company
Part Number
AWG.
Anixter
F-02P22BPN
22
Tel: 847-677-2600
www.anixter.com
3. Wiring connections are made as shown in FIGURE
4-2
. Note wires
labeled A and B are one twisted pair of the cable. Wires labeled C and D
are the other twisted pair.
4. Transients induced on the communication line may damage any
electronics connected at either end of the line. To decrease the chances for
damage, spark gaps should be installed as shown in FIGURE
4-2
. The
