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Teledyne API – Model T700 Dynamic Dilution Calibrator Principles of Operation
297
UV Lamp
UV Lamp
Thermistor
O
3
Generator
Heater Control PCA
(Heater is located beneath
the PCA)
Figure 10-16: O
3
Generator Temperature Thermistor and DC Heater Locations
10.6.3.2. Pneumatic Sensor for the O
3
Generator
A pressure sensor, located on the O
3
generator and photometer, pressure/flow sensor
PCA (see Figure 3-6), monitors the output gas pressure of the regulator on the O
3
generator’s zero air supply. The regulator is adjusted at the factory to maintain a
pressure of 20 PSIG on this line. If the pressure drops below 15 PSIG or rises above 25
PSIG a warning is issued.
10.7. PHOTOMETER OPERATION
The Model T700 calibrator’s optional photometer determines the concentration of
Ozone (O
3
) in a sample gas drawn through it. Sample and calibration gases must be
supplied at ambient atmospheric pressure in order to establish a stable gas flow through
the absorption tube where the gas’ ability to absorb ultraviolet (UV) radiation of a
certain wavelength (in this case 254 nm) is measured.
Gas bearing O
3
and zero air are alternately routed through the photometer’s absorption
tube. Measurements of the UV light passing through the sample gas with and without
O
3
present are made and recorded.
Calibration of the photometer is performed in software and does not require physical
adjustment. During calibration, the CPU’s microprocessor measures the current state of
the UV Sensor output and various other physical parameters of the calibrator and stores
them in memory. The CPU uses these calibration values, the UV absorption
06873B DCN6388