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Oil in Water Analyzer Maintenance 3
Part II 3-7
Teledyne Analytical Instruments
3.5.8 Integrated Reference and Measuring Signals
You can observe the reference and measuring signal at the first stage of
integration by connecting the scope probe to TP6 (reference signal) and TP7
(measuring signal) at the detector unit. A dual trace scope is advantageous but
not required for this observation.
The test points’ significance is that they reveal proper switch action. The
display shows a sawtooth pattern that is a charge-discharge of the first capacitor
in the integrating network. This ripple is the AC component of the reference and
measuring signal after the pulses are converted to DC. The sawtooth patterns
must be displayed 180° with respect to each other as viewed with a dual trace
scope. They must both be present.
If one is missing, the switch is not switching. If the sawtooth shows a
broken pattern, the switching action is feeble or irregular. Usually, you can fix
the faulty condition of the switch by slightly changing the switch position.
The action of a bar magnet and a rotating chopper disc activate
themagnetic mercury reed switch. An aluminum motor mounting block houses
a bar magnet. This bar magnet is parallel with the mercury chopper switch.
The chopper disc is a green and black disc mounted on the filter wheel
shaft next to the motor. The disc is composed of both magnetic and non-
magnetic materials. As the shaft rotates, the magnetic portion of the disc shorts
the magnetic flux as it passes between the magnet and the switch. The non-
magnetic portion of the disc enables flux lines from the bar magnet to activate
the mercury switch.
3.5.9 Battery-Powered Oscilloscope
Synchronization Point
Because the line frequency cannot synchronize battery-powered oscillo-
scopes, use TP8 at the detector module to provide external synchronization.
3.6 Interface Board Terminals Strip
At the bottom of the interface PCB on the Control/Analysis Unit, are
three terminal strips where wiring is distributed to other sections of the
Model 6600 System. Such as AC power for the D2 lamp power supply, DC
Power to the preamplifier, High DC voltage for the photodetector, and