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Principles of Operation Teledyne API – Model T700 Dynamic Dilution Calibrator
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The core of the calibrator is a microcomputer (referred to as the 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 is directly mounted to the inside rear panel and collects data, performs
signal conditioning duties and routes incoming and outgoing signals between the CPU
and the calibrator’s other major components.
Data are generated by the various sub components of the T700 (e.g. flow data from the
MFCs, O
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concentration from the optional photometer). Analog signals 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 calibrator’s major
components, again through the signal processing capabilities of the motherboard. These
status reports are used as data for the concentration calculations 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 calibrator’s front panel LCD touchscreen interface;
RS 232 and RS485 serial I/O channels;
Via Ethernet;
Various digital and analog outputs, and
A set of digital control input 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 to control the function of key
electromechanical devices such as heaters, motors and valves.
10.3.2. CPU
The unit’s CPU card (Figure 10-4) is installed on the motherboard located inside the rear
panel. It 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 and features the following:
06873B DCN6388