17
readouts will reset to zero and the unit will remain in
ZERO/STANDBY
until the
CHARGE
button is depressed.
5. When testing of a sample has been completed, the High Voltage
Power Supply should be turned off by depressing the
HIGH
VOLTAGE OFF
button. When this is done, the
CHARGING
VOLTAGE
meter will indicate zero and the
HIGH VOLTAGE ON
light
will turn off. The HVPS should be turned
OFF
whenever a sample is
being installed in, or removed from, the Faraday Cage or when the
unit is on but tests are not being conducted.
6. Faraday Cage Safety Interlock System - The Model 406D contains a
Safety Interlock System which is designed to prevent the Control Unit
from producing a high voltage output under certain conditions. The
Interlock System operates automatically whenever the cover of the
Faraday Cage is raised by preventing the Control Unit from producing
a high voltage output at the
HIGH VOLTAGE
output connector. The
Interlock System, when activated, does not turn off the High Voltage
Power Supply in the Control Unit, thus, ±5kV may still be present
within the Control Unit when the Faraday Cage cover is up. It causes
the CHARGE relay to open and the GROUND relay to close.
It should be emphasized again that the Interlock System is a safety
feature and should not be used as a High Voltage
ON/OFF
switch.
The
HIGH VOLTAGE OFF
button should be depressed whenever the
Faraday Cage cover is lifted or when tests are not being conducted.
3.3.4 STM System Performance Check
To check the performance of the Model 406D Static Decay Meter, the
STM
System Test Module is mounted in the Faraday Cage in place of a
normal test sample.
3.3.4.1
STM-1 (Systems prior to Serial #878)
For the
STM-1
the banana plug is inserted into the calibration jack
on the base of the Faraday Cage as shown in Figure 3.2-1. It is
important to insure that the banana plug is fully seated in the jack.
The calibration check may be performed in either the
MANUAL
or
the
AUTOMATIC
mode. Select the appropriate test mode and
follow the test procedure outlined in Section 3.2 for the
MANUAL
mode or Section 3.3 for the
AUTOMATIC
mode. In either mode,
the
CUTOFF
threshold should be set to 10% to obtain the proper
calibrated mode decay time reading. When setting the
SAMPLE
CHARGE
meter to full scale in the
CHARGE
state (5.0kV), it will
be necessary to turn the
FULL SCALE ADJUST CONTROL
to
the
STM-1
position. If a 5.0kV reading cannot be obtained, loosen
the thumbscrew securing the electrostatic sensor in the test cage
and either push it in slightly or rotate it so the viewing port is lined
up in the 12:00 o’clock position until a full scale reading on the
SAMPLE CHARGE
meter is obtained. Retighten the screw. If the
sensor viewing port is already in the 12:00 o’clock position, make
