3)
For pinhole detection of thick materials, the spark should be adjusted
for near maximum length. For thinner materials, a shorter spark is
desired. A one inch spark represents a peak voltage of approximately
50,000 volts. For materials less than 1/8 in. (3 mm), use the Model
BD-40E or Model BD-60. For vacuum leak checking, an output near
the maximum is usually required to ionize (glow) the gas inside the
container.
4)
Once the unit is adjusted, pass the electrode over the material being
tested. The electrode can be passed directly over most materials,
however, with thin linings or glass, keep the electrode no more than
1/8 in. above the surface being tested.
5)
When the electrode passes over a pinhole, crack, or similar type flaw,
observe a bright, concentrated spark jumping from the electrode to the
metal, or similarly conducting surface below the lining or coating.
Do not use the Voltage Adjustment Knob as an “ON/OFF” switch for
the high voltage, as this will prematurely wear this part. Never leave
either model connected to the power line unattended. Remove from
the power line when not in use. Use of a power strip with ON / OFF
Switch is recommended.
If the output level of the Model BD-10A/BD-10AS is required to be verified when
this instrument is in use, check the output with a Model 12701 Peak Voltage
Calibrator, shown below.
THEORY OF OPERATION.
The output of the Model BD10A/AS is adjusted by
changing the gap between two contacts, one vibrating due to the magnetic pull
and push from a coil, and the other connected to a screw with black knob at the
end of the unit. The vibrating contact assembly consists of the contact, spring,
and metal plug to which the magnetic field attracts and repels. The other contact
assembly is held in place by a flexible spring connected to a shaft and the black
control knob. Its position is determined by the adjustment, in or out, of the
connecting shaft.
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