SC932A CS I/O to RS-232-DCE Interface
6
Occasionally, a customer needs to transmit data across longer or smaller gage
wires or at higher speeds than can be done with the RAD modem powered by
the SC932A. RAD does sell a 9-volt power supply that will boost the signals
enough to meet some of these more demanding applications. Please contact
RAD for more information.
4.3 Testing RAD Modem Communication
The modem communication link is divided into the following three sections:
1) RAD modem computer end, 2) cable from computer modem to datalogger
modem, and 3) RAD modem datalogger end. When unable to establish
communication with the datalogger, test each of the three sections.
Before proceeding through the testing procedures, a terminal emulator software
program such as
HyperTerminal
or Campbell Scientific’s
Terminal Emulator
(included with
PC200W
,
PC400
, and
LoggerNet
) must be used to communicate
through the COM port of the computer. Once the emulator program is set up,
testing can proceed as follows:
1. Disconnect the four conductor cables from the SRM-6A RAD modem at
the computer end. Jumper the XMT + to RCV + and jumper the XMT – to
RCV –. This creates a transmit loop which allows any key pressed at the
computer keyboard to be seen on the screen. If the key pressed is not seen,
check the following: COM port configuration, 25-pin cable from the
computer to the modem and the RAD modem.
2. Reconnect the four conductor cables to the modem at the computer end
and disconnect the cable from the modem at the datalogger end. Twist
together the XMT + wire and RCV + wire, twist together the XMT – wire
and the RCV – wire. Repeat the process of step 1 by pressing a key on the
computer keyboard. If the key pressed is not returned, then the cable from
the modem at the computer to the datalogger modem is defective and will
need to be repaired or replaced.
3. If steps 1 and 2 pass, the modem at the datalogger is suspect. Disconnect
the modem from the SC932A and bring the modem to the computer site.
Attach the modem to the computer, and repeat step 1 by jumpering the
terminals of the modem and pressing a key on the computer keyboard.
If the above tests pass and communication to the datalogger still has not been
established, perform tests 4, 5, and 6.
4. A 12 V lead acid battery supply should not be discharged below 11.76 V.
If this occurs, the batteries will go into a deep discharge state and will
need to be replaced. The CR10 will function properly on a battery voltage
of 10 to 15 volts. Check the 12 V supply with a volt meter.
5. On the wiring panel of most Campbell Scientific dataloggers there is a
terminal marked 5 V. Check the 5 V supply with a volt meter. This 5 V
supply should be within a tenth of a volt. If not, it would indicate a
problem.
6. To verify that the datalogger and its serial I/O port are working, try to
access input memory locations using a laptop PC with the SC32B or the
CR10KD Keyboard Display.
If the datalogger passes tests 4, 5, and 6, then the SC932A is suspect and will
need to be repaired or replaced.
