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Oil in Water Analyzer Maintenance 3
Part II 3-5
Teledyne Analytical Instruments
3.5.5 Balancing the Optics for Equal Light Transmission
with Zero Fluid in the SAMPLE CELL
The objective of this procedure is to obtain measuring and reference
peak heights as displayed on the oscilloscope that are approximately equal, with
the tallest peaks set at 8 to 9 volts. This must be done with zero fluid in the cell.
(Collect a Zero prepared fluid from the sample system ifor all oil in water
analyzers). See Part III, Section 5.5
The procedure is purely mechanical and consists of adjusting the amount
of light passing through either the measuring or reference filter, never both.
Screens (wire mesh) of varying density are used for this operation and are part
of the small took kit accompanying the instrument.
1. Observe the oscilloscope and judge if optical balancing is
needed. When the difference is less than 1 volt, balancing is not required. The
tallest of the two peaks should be adjusted to 8 or 9 volts with the gain control
R2 on the detector PC board. When this cannot be done because both peaks are
too short or too long, search for screens mounted in the light path, usually located
in a holder on the light pipe which interconnects the detector and sample module,
and remove or add screens, as necessary.
2. When balancing is needed, identify the peaks as outlined under
Section
3. For example, if the reference peak is the shorter one, stop the
filter wheel with your hand and see if screens are located behind the reference
filter. The reference filter is identified by the letter “R” engraved on the filter
wheel.
4. If screens are found, remove them after taking the filter wheel off
the shaft with the special Allen wrench supplied in the tool kit.
5. After removal of the screens and remounting the filter, mount the
filter wheel back on the shaft. Position it correctly on the shaft by lining up the
two paint marks on shaft and wheel.
6. Turn on the instrument and observe the balance on the oscillo-
scope.
a. If the reference peak is now too tall, remove the filter wheel and
add a screen of lesser density behind the reference filter. Repeat this procedure
until the peaks are within 1 volt of each other.