Teledyne GFC-7001T - Trace CO Analyzer - Manual (Page 152)

CommunicationsTeledyne API – Model T300/T300M CO Analyzer
Teledyne Analytical Instruments 152
6.7.2. HESSEN
The Hessen protocol is a multidrop protocol, in which several remote instruments are
connected via a common communications channel to a host computer. The remote
instruments are regarded as slaves of the host computer. The remote instruments are
unaware that they are connected to a multidrop bus and never initiate Hessen protocol
messages. They only respond to commands from the host computer and only when they
receive a command containing their own unique ID number.
The Hessen protocol is designed to accomplish two things: to obtain the status of remote
instruments, including the concentrations of all the gases measured; and to place remote
instruments into zero or span calibration or measure mode. TAI’s implementation
supports both of these principal features.
The Hessen protocol is not well defined, therefore while TAI’s application is completely
compatible with the protocol itself, it may be different from implementations by other
companies.
Note The following sections describe the basics for setting up your instrument
to operate over a Hessen Protocol network.
For more detailed information as well as a list of host computer
commands and examples of command and response message syntax,
download the Manual Addendum for Hessen Protocol from the Teledyne
web site: http://www.teledyne-api.com/manuals/.
6.7.2.1. HESSEN COMM PORT CONFIGURATION
Hessen protocol requires the communication parameters of the GFC7001T/GFC7001TM
Analyzer’s COMM ports to be set differently than the standard configuration as shown
in Table 6-4.
Table 6-4: RS-232 Communication Parameters for Hessen Protocol
PARAMETER STANDARD HESSEN
Baud Rate 300 – 19200 1200
Data Bits 8 7
Stop Bits 1 2
Parity None Even
Duplex Full Half
To change the baud rate of the GFC7001T/GFC7001TM’s COMM ports, see Section
6.2.2.
To change the rest of the COMM port parameters listed in Table 6-4, see Section 6.2 and
Table 6-1.
I
MPORTANT I MPACT ON R EADINGS OR D ATA
Ensure that the communication parameters of the host computer are also
properly set.