Filter
Top Products
2635A
Users Manual
6-8
Testing the RS-232/Modem Interface
The PC end of the modem link involves a similar procedure of connecting the correct
cable between the PC and modem, and configuring the modem to support the
communications link. This is the responsibility of the user due to the variety of available
modems and software. Be sure the PC COM port has the same parameters as those
selected in Figure 6-4.
When all connections and configurations are complete, the PC should initiate
communications with the modem supporting the instrument using the selected
communications software. Typically, this means selecting a dial feature, or entering an
AT command, e.g., ATDT 123-4567 from the terminal emulation screen. After the
connection is made and the terminal emulation screen is present, enter a few <ENTER>
characters to clear the instrument buffer, and note the instrument => prompts on the
screen. Then enter the command *IDN? <ENTER> (since ECHO OFF was selected in
Figure 6-4, the *IDN? characters will not appear on screen). The return should be
FLUKE,2635A,0,Mn.n An.n Dn.n Ln.n where n.n is replaced with the versions of the
displayed parameters. (See the *IDN? command in Chapter 4 for more information.)The
RS-232/modem link is operating correctly and the PC may now operate using Starter or
Logger applications software, or custom software.
Problems?
If the modem does not operate after making the RS-232 connection, telephone line
connections, and setting the instrument and PC parameters, check the following:
1. No operation of any kind usually indicates a cabling problem, hardware
incompatibility, a modem DIP switch problem, or incorrectly selecting ECHO ON in
Figure 6-4 (ECHO OFF must be selected).
2. Incorrect operation usually indicates a configuration incompatibility, i.e., the
instrument and PC baud rate and parity don’t match.
3. Verify the modem configuration data hasn’t been lost or corrupted. Some modems
use an internal battery to retain configuration data when power is removed, and some
modems lose configuration data if power is removed. If the configuration data is
suspect, repeat the configuration procedures in this chapter.