Teledyne 9110TH - Nitrogen Oxides Analyzer - Manual (Page 258)

Model 9110TH NOx Analyzer Troubleshooting & Repair
Teledyne Analytical Instruments 238
7.5.12. RS-232 COMMUNICATION
7.5.12.1. General RS-232 Troubleshooting
TAI analyzers use the RS-232 protocol as the standard, serial communications protocol.
RS-232 is a versatile standard, which has been used for many years but, at times, is
difficult to configure. TAI conforms to the standard pin assignments in the
implementation of RS-232. Problems with RS-232 connections usually center around 4
general areas:
 Incorrect cabling and connectors. This is the most common problem. See
Section 4.11.5 for connector and pin-out information.
 The communications (baud) rate and protocol parameters are incorrectly
configured. See Section 4.11.3.2 on how to set the baud rate.
 The COM port communications mode is set incorrectly (Section 6.11.8).
 If a modem is used, additional configuration and wiring rules must be
observed. See Section 6.15.2.6.
 Incorrect setting of the DTE - DCE switch. Typically, the red LED is on as
soon as you power up the analyzer. If not, contact the factory, as this
indicates a problem with the motherboard. As the analyzer is connected to
the computer with a cable, the green LED should also illuminate. If not, set
the DCE/DTE switch to the other position. See also Section 6.11.5.
 that some laptops do not enable their RS-232 port when in power-saving
mode. In this case, connect the laptop and start either APICOM or a
Hyperterminal window and start communicating with the analyzer. This
will enable the serial port on the laptop and the green LED should
illuminate. You may have to switch back and forth while communicating to
get the right setting.
7.5.12.2. Modem or Terminal Operation
These are the general steps for troubleshooting problems with a modem connected to a
Teledyne API analyzer.
 Check cables for proper connection to the modem, terminal or computer.
 Check the correct position of the DTE/DCE as described in Section 6.11.5.
 Check the correct setup command (Section 6.15.2.6).
 Verify that the Ready to Send (RTS) signal is at logic high. The 9110TH/M
sets pin 7 (RTS) to greater than 3 volts to enable modem transmission.
 Make sure the baud rate, word length, and stop bit settings between modem
and analyzer match, see Section 6.15.2.6 and 6.11.8.