Pneumatic Sensors; Sample Pressure Sensor; Sample Flow Sensor; Electronic Operation - Teledyne T400 User Manual

6.2.4 P
NEUMATIC
There are two pneumatic sensors: one each to measure sample pressure and flow.
6.2.4.1

SAMPLE PRESSURE SENSOR

An absolute value pressure transducer plumbed to the outlet of the sample chamber is
used to measure sample pressure. The output of the sensor is used to compensate the
concentration measurement for changes in air pressure. This sensor is mounted to a
printed circuit board next to the internal pump.
6.2.4.2

SAMPLE FLOW SENSOR

A thermal-mass flow sensor is used to measure the sample flow through the analyzer.
The sensor is located downstream from the absorption tube but upstream from the critical
flow orifice. This sensor is mounted to the same printed circuit board as the pressure
sensor.
6.3

ELECTRONIC OPERATION

Figure 6-5 shows a block diagram of the major electronic components of the analyzer.
The core of the analyzer is a microcomputer/central processing unit (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 analyzer's 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
measure gas and a voltage level corresponding to the lack of O
This signal is transformed 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 O
for certain control commands issued by the CPU. This information is stored in memory
by the CPU and in most cases can be viewed but the user via the front panel display.
The CPU issues commands via a series of relays and switches (also over the I
located on a separate printed circuit assembly to control the function of key
electromechanical devices such as heaters, motors and valves.
The CPU communicates with the user and the outside world in several ways:
Through the analyzer's front panel capacitive touch-screen interface
•
• Serial I/O
Several digital I/O channels
•
• Ethernet
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S
ENSORS
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Teledyne API – Model T400 O
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083730400A DCN8130