Teledyne GFC-7000T - Trace CO2 Analyzer - manual - Manual (Page 171)

Operating Instructions Model GFC7000TA Carbon Dioxide Analyzer
Teledyne Analytical Instruments 153
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
NUMBER
AVAILABLE ONLINE*
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 .