SC105 CS I/O to RS-232 Interface
8
communication with the data logger, test each of the three sections. See a blog
article at:
www.campbellsci.com/blog/test-com-ports-short-haul-modems
Before proceeding through the testing procedures, a terminal emulator software
program such as Campbell Scientific Terminal Emulator (included with
LoggerNet, PC400 and Device Configuration Utility) 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 data logger 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 data logger modem is defective and will
need to be repaired or replaced.
3. If steps 1 and 2 pass, the modem at the data logger 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 data logger 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. Check the 12 V supply with a voltmeter.
5. On the wiring panel of most Campbell Scientific data loggers 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 data logger 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.
If the data logger passes tests 4 and 5, but fails test 6, then the SC105 is suspect
and will need to be repaired or replaced.
