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Teledyne API – Model T700 Dynamic Dilution Calibrator Getting Started
65
CONSTANT mode: By selecting a specific, constant drive voltage (corresponding to
a specific O
3
concentration) for the generator, or;
REFERENCE mode: The user selects a desired O
3
concentration and the
calibrator’s CPU sets the intensity of the O
3
generator’s UV lamp to an intensity
corresponding to that concentration. The voltage output of a reference detector,
also internal to the generator, is digitized and sent to the T700’s CPU where it is
used as input for a control loop that maintains the intensity of the UV lamp at a level
appropriate for the chosen set point.
See Section 10.6 for more details on the operation of the O3 generator.
In addition to the diluent gas, calibration source gas, and gas output connections
discussed in the preceding sections, this option also requires an O3 exhaust line be
connected to the EXHAUST outlet on the back of the T700 (see Figure 3-4).
Note
The EXHAUST line must be vented to atmospheric pressure using maximum of
10 meters of ¼” PTEF tubing.
Venting must be outside the shelter or immediate area surrounding the
instrument..
O
3
GENERATOR WITH PHOTOMETER OPTION
The photometer option increases the accuracy of the T700 calibrator’s optional O
3
generator (OPT 1A) by directly measuring O
3
content of the gas output by the generator.
The photometer’s operation is based on the principle that ozone molecules absorb UV
light of a certain wavelength. A mercury lamp internal to the photometer emits UV light
at that wavelength. This light shines down a hollow glass tube that is alternately filled
with sample gas (the measure phase), and zero gas (the reference phase). A detector,
located at the other end of the glass tube measure the brightness of the UV light after it
passes though the gas in the tube. The O
3
content of the gas is calculated based on the
ratio the UV light intensity during the measure phase (O
3
present) and the reference
phase (no O
3
present).
When the photometer option is installed, a third more precise and stabile option, called
the BENCH feedback mode, exists for controlling the output of the O
3
generator. In
BENCH mode the intensity of the O
3
generator’s UV lamp is controlled (and therefore
the concentration of the O
3
created) by the T700’s CPU based on the actual O
3
concentration measurements made by the photometer.
See Section 10.7 for more details on the operation of the O
3
photometer.
This option requires that the O
3
generator (OPT 1A) be installed.
06873B DCN6388