Teledyne T802 12.5. ELECTRONIC OPERATION

Principles of Operation Teledyne API T802 Paramagnetic O2 Analyzer Operation Manual

226

compensate the concentration measurement for changes in ambient air pressure.

This sensor is mounted to a printed circuit board with the sample flow sensor on

the sample chamber; see the following section and Figure 3-5.

12.4.3.2. SAMPLE FLOW SENSOR

A thermal-mass flow sensor is used to measure the sample flow through the

analyzer. The sensor is calibrated at the factory with ambient air or N2, but can

be calibrated to operate with samples consisting of other gases such as O2. This

sensor is mounted to a printed circuit board with the Sample Pressure sensor on

the sample chamber; see the previous section and Figure 3-5.

12.5. ELECTRONIC OPERATION

Figure 10-9 shows a block diagram of the major electronic components of the

T802.

At its heart the analyzer is a microcomputer (CPU) that controls various internal

processes, interprets data, makes calculations, and reports results using

specialized firmware developed by Teledyne API. 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 O2 in the sample gas. This

analog signal is 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 O2 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 DCV and DCA analog outputs, and

 Several sets of Digital I/O channels.

07275B DCN6418