Campbell Scientific SC105 9-pin to RS232 DCE Interface - Manual (Page 12)

SC105 CS I/O to RS-232 Interface
TABLE 5-1. 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
5.1 RAD Modem – Two Way
4-WIRE UNCONDITIONED
TELEPHONE LINE
OR
TWO TWISTED PAIRS
SRM
9 TO 25 PIN
ADAPTOR SC105 DATALOGGER PC SRM
FIGURE 5-1. Two Way Communication
When using Campbell Scientific’s datalogger support software to communicate
through the SC105/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 tool bar and the Connect button in the Connect
window.
5.2 RAD Modem Wiring and Grounding
FIGURE 5-2 shows a typical set-up of the RAD modems. Installation is as
follows:
1. Set the DCE/DTE switch on the back of the RAD modem connected to
the SC105 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 5-2. 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 5-2. The
transient protection shown may be purchased from Campbell Scientific
(pn 5563 shown in FIGURE 5-2, pn 6536 includes a plastic case, pn 6361
includes hardware for mounting to ground lug of Campbell Scientific
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