Teledyne gfc 7000ta Additional Communications Documentation, General Overview of Hessen Protocol

Operating Instructions Model GFC7000TA Carbon Dioxide Analyzer

APICOM is included free of cost with the analyzer and the latest versions can also be downloaded for free at http://www.teledyne-api.com/software/apicom/.

6.15.3. Additional Communications Documentation

Table 6-28: Serial Interface Documents

INTERFACE / TOOL	DOCUMENT TITLE	PART	AVAILABLE ONLINE*
		NUMBER
APICOM	APICOM User Manual	039450000	YES
DAS Manual	Detailed description of the DAS.	028370000	YES

* These documents can be downloaded at http://www.teledyne-api.com/manuals/

6.15.4. Using the GFC 7000TA with a Hessen Protocol Network

6.15.4.1. 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. 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.

The following subs 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 Instruments web site: http://www.teledyne-api.com/manuals/index.asp .

Teledyne Analytical Instruments 153