System Adjustments - Electro-Tech systems 406D Operating Manual

Laminated materials such as static shielding film may consist of two or more
layers with one layer being conductive. This composite alters the way the static
decay time is measured. When testing this type of material the edges must
not touch the electrodes. The samples must be cut oversize (6x6"
[150x150mm]) plus the FULL SCALE adjust must be precisely set using a
piece of aluminum foil stretched between the electrodes. This control must
not be changed during the measurement. The following are the different types
of measurements observed when testing this material:
1. Conductive layer facing sensor: The conductive layer will become charged
to the full 5kV and when grounded will decay almost instantly to 1% in <1 or
2 msec.
2. Dissipative or insulative layer facing sensor: If this layer is dissipative it
will charge to the full 5kV and when grounded will have a measurable decay
time, usually in the millisecond range. If this layer is insulative the applied
charge will be induced onto the surface of the conductive layer and the
SAMPLE CHARGE meter will indicate a accepted charge that is less than
5kV, typically, around 4.8kV. When grounded, the charge on the conductive
layer collapses and the SAMPLE CHARGE meter drops instantly to some
voltage slightly above the 1% cutoff level, typically, about 1-200V. In this
case, the clock will continue to run. Note: The amount of accepted charge will
decrease and the residual charge will increase as the insulated layer
thickness increases.
3. Triple laminate: This material will perform in a similar manner as the
dissipative or insulated side for the two-layer film described above.

5.0 SYSTEM ADJUSTMENTS

The Model 406D Static Decay Meter, like all precision electronic instruments, should be
returned to the factory once a year for calibration. However, due to heavy use or having
been moved to another location the instrument may require some minor adjustments in
the interim. This section covers adjustment of FULL SCALE.
The FULL SCALE adjustment is performed externally by adjusting system gain or the
distance between sensor and sample.
5.1 SAMPLE CHARGE Meter Zero Adjust
5.1.1 Zero (Mechanical Center Scale Adjustment)
1. Turn the power off and allow the SCm zero reading to stabilize for at
least 30 seconds.
2. Using a small flat bladed screw driver, set the SCm to read precisely
zero by adjusting the black mechanical center adjust screw located on
the face of the meter at the pivot point of the needle. Make sure the
unit is in a horizontal position while making this and the full-scale
adjustment that follows.
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