Teledyne GFC 7001E User Manual download pdf (Page 175)

Remote Operation Model GFC7001E Carbon Dioxide Analyzer

Teledyne Analytical Instruments 175

8.6. USING THE GFC 7001E/EM WITH A HESSEN PROTOCOL

NETWORK

8.6.1. GENERAL OVERVIEW OF HESSEN PROTOCOL

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. ‘s implementation supports both of these principal features.

The Hessen protocol is not well defined, therefore while’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/.

8.6.2. HESSEN COMM PORT CONFIGURATION

Hessen protocol requires the communication parameters of the GFC 7001E/EM Analyzer’s COMM ports to be

set differently than the standard configuration as shown in Table 8-6.

Table 8-6: 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 GFC 7001E/EM’s COMM ports, see Section 8.1.3.

To change the rest of the COMM port parameters listed in the Table 8-6. Also see Section 8.1 and Table 8-1.

Note

Make sure that the communication parameters of the host computer are also properly set.

Also, the instrument software has a 200 ms latency period before it responds to commands issued by

the host computer. This latency should present no problems, but you should be aware of it and not

issue commands to the instrument too frequently.

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Teledyne GFC 7001E User Manual Page 175