Teledyne GFC 7001EM operation manual Electronic Operation, Overview

Theory of Operation Model GFC7001E Carbon Dioxide Analyzer

11.5.ELECTRONIC OPERATION

11.5.1.OVERVIEW

Figure 11-9 shows a block diagram of the major electronic components of the GFC 7001E/EM.

At the heart of the analyzer is a microcomputer/CPU that controls various internal processes, interprets data, makes calculations, and reports results using specialized firmware developed by Teledyne. It communicates with the user as well as receives data from and issues commands to a variety of peripheral devices via a separate printed circuit assembly called the motherboard.

The motherboard collects data, performs signal conditioning duties and routes incoming and outgoing signals between the CPU and the analyzer’s other major components.

Data is generated by a gas-filter-correlation optical bench which outputs an analog signal corresponding to the concentration of CO in the sample gas. This analog signal is transformed into two, pre-amplified, DC voltages (CO MEAS and CO REF) by a synchronous demodulator printed circuit assembly. CO MEAS and CO REF are converted into digital data by a unipolar, analog-to-digital converter, located on the motherboard.

A variety of sensors report the physical and operational status of the analyzer’s major components, again through the signal processing capabilities of the motherboard. These status reports are used as data for the CO concentration calculation and as trigger events for certain control commands issued by the CPU. They are stored in memory by the CPU and in most cases can be viewed but the user via the front panel display.

The CPU communicates with the user and the outside world in a variety of manners:

Through the analyzer’s keyboard and vacuum florescent display over a clocked, digital, serial I/O bus (using a protocol called I2C);

RS-232 & RS-485 Serial I/O channels;

Via an optional Ethernet communications card:

Various analog and current analog outputs, and

Several sets of Digital I/O channels.

Finally, the CPU issues commands via a series of relays and switches (also over the I2C bus) located on a separate printed circuit assembly to control the function of key electromechanical devices such as heaters, motors and valves.

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