SC105 CS I/O to RS-232 Interface
5.3 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, 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
TM
or Campbell Scientific’s datalogger support
software (
Test Terminal Emulator
) 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 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 SC105 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 voltmeter.
5. On the wiring panel of most Campbell Scientific dataloggers there is a
terminal marked 5 V. Check the 5 V supply with a voltmeter. 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 SC105 (using a
null modem cable connection). Configure the SC105 CS I/O Port to
Modem Enable for this test.
7. If test 6 fails, use a CR10KD Keyboard Display to access input locations.
If the datalogger passes tests 4, 5, and 7, but fails test 6, then the SC105 is
suspect and will need to be repaired or replaced.
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