14
Table 3.1
Cutoff Levels and Applicable Specifications
*
Nominal value. Actual cutoff is the percentage selected by the
CUTTOFF
selector. Ex: Accepted voltage is 4.5kV, cutoff is 450V.
3. With the unit in
ZERO/STBY
, set the
SAMPLE CHARGE
meter to zero by
adjusting the
ZERO
calibrate control.
4. With the High Voltage
OFF
, depress the
CHG
button and check the reading
of the
SAMPLE CHARGE
meter. It should still read precisely zero. If there is
movement of the
SAMPLE CHARGE
meter needle (approx 250V), the test
sample may have an initial charge. Refer to Section 4.0 for additional
information on test samples with an initial charge. Select the desired polarity
of the charging voltage by depressing either the
CHARGING V
or
-
polarity button.
5. Rotate the High Voltage
ADJUST
control clockwise to set the charging
voltage to the desired level. ±5kV is the most commonly used test voltage
and the system has been calibrated for testing at this level. The charging
voltage level will be indicated on the
CHARGING VOLTAGE
meter, and the
HI VOLTAGE ON
indicator will be illuminated. For those systems modified to
meet CECC 00015 requirements, the 1kV test voltage will produce a full
scale reading on the
SAMPLE CHARGE
meter.
NOTE
: There is an approximate 2 second delay after a polarity button has
been depressed before the
CHARGING VOLTAGE
meter will read. This is
normal. It allows the previously selected voltage to bleed down to zero before
switching to the opposite polarity.
6. Calibrate the
SAMPLE CHARGE
meter to either
+
or
-
5kV (full scale setting)
using the
STM-2,
or if supplied with a
STM-1,
a piece of foil or a known
sample with good dissipative characteristics having the same shape as the
samples being tested. For example, bubble material. After this full-scale
calibration the
FULL SCALE ADJUST
control
must not be changed
during
the test run.
7. Depress the
TEST
button to start the Decay Time measurement. The
electrostatic sensor shutter will close momentarily, then open to start the
decay time measurement. The HVPS will automatically turn off as indicated
by the
CHARGING VOLTAGE
meter reading dropping to zero and the
HIGH
VOLTAGE ON
indicator turning off.
NOTE:
If the
TEST
button is not depressed within approximately 3 minutes
after the
CHARGE
button is depressed, the unit will automatically switch
back to the
ZERO/STBY
state. To resume the test sequence, if this occurs,
CUTOFF
THRESHOLD
CUTOFF
VOLTAGE
*
APPLICABLE
SPECIFICATION
50%
2500
Half Life
10%
500
NFPA Code 99
1%
50
Mil-PRF-81705C, EIA & ESDA 541
