Filter
Top Products
Theory of Operation T400 Ozone Analyzer Operator’s Manual
284
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 routs incoming
and outgoing signals between the CPU and the analyzers other major components.
An analog signal is generated by an optical bench that includes the Photometer UV
Lamp, the Absorption Tube assembly and the UV Detector and Preamp. This signal
constantly cycles between a voltage level corresponding to concentration of O
3
in the
measure gas and the one corresponding to the lack of O
3
in the reference gas. This
signal is transformed converted into digital data by a unipolar, analog-to-digital
converter, located on the motherboard.
A variety of sensors report other critical operational parameters, again through the signal
processing capabilities of the motherboard. This data is used to calculate O
3
concentration and as trigger events for certain warning messages and 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 touchscreen and Liquid Crystal Display (LCD) over a
clocked, digital, serial I/O bus (using a protocol called I
2
C);
RS 232 & RS485 Serial I/O channels;
Various DCV and DCA 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 I
2
C
bus) located on a separate printed circuit assembly, called the relay PCA, to control the
function of button electromechanical devices such as heaters and valves.
13.3.2. CPU
The unit’s CPU card, installed on the motherboard located inside the rear panel, is a low
power (5 VDC, 720mA max), high performance, Vortex86SX-based microcomputer
running Windows CE. Its operation and assembly conform to the PC 104 specification.
06870C DCN6332