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Principles of Operation Teledyne API T703/T703U Calibrator Operation Manual
218
9.6.4.1. O
3
Photometer Temperature Control
In order to operate at peak efficiency the UV lamp of the O
3
photometer is maintained at
a constant 58ºC. This is intentionally set at a temperature higher than the ambient
temperature of the operating environment to make sure that local changes in temperature
do not affect the UV Lamp. If the lamp temperature falls below 56ºC or rises above
61ºC a warning is issued by the calibrator’s CPU.
This temperature is controlled as described in the section on the relay PCA (Section
9.2.3.2).
The following TEST func
tions report these temperatures and are viewable from the
instrument’s front panel:
PHOTO LAMP TEMP - The temperature of the UV Lamp reported in ºC.
PHOTO STEMP - The temperature of the Sample gas in the absorption tube
reported in ºC.
9.6.4.2. Pneumatic Sensors for the O
3
Photometer
The several sensors located on the pneumatic sensor just to the left rear of the O
3
generator assembly measure the absolute pressure and the flow rate of gas inside the
photometer’s absorption tube. This information is used by the CPU to calculate the O
3
concentration of the sample gas (See Equation 9-7). Both of these measurements are
made downstream from the absorption tube but upstream of the pump. A critical flow
orifice located between the flow sensor and the pump maintains the gas flow through the
photometer at 800 cm
3
/min.
The following TEST functions are viewable from the instrument’s front panel:
PHOTO FLOW - The flow rate of gas through the photometer measured in LPM.
PHOTO SPRESS – the pressure of the gas inside the absorption tube. This
pressure is reported in inches of mercury-absolute (in-Hg-A), i.e. referenced to a
vacuum (zero absolute pressure). This is not the same as PSIG.
07223C DCN6572