7
2.2.4.3
TEST
This momentary push button switch, when depressed, steps the
system from the
CHARGE
state to the
TEST
state. Here, the
shutter in the sensor of the Electrostatic Voltmeter is open, the
High Voltage Power Supply is turned off, the discharge relay is
closed, causing the charge on the sample to start to decrease, and
the
DECAY TIME
counter is activated allowing the sample decay
time to be measured. In the
AUTO MODE
, the
TEST
button is not
used since the unit will automatically step to the
TEST
state after
the
CHARGE
button is depressed.
2.2.5 High Voltage Control
2.2.5.1.High Voltage
ADJUST
This control is used to set the Charging Voltage level. It is
continuously variable and enables the charging voltage to be set to
any level from 0 to ±5 kV. When in either
ZERO/STBY
or
CHG
, the
high voltage level set by the
ADJUST
control is indicated by the
reading on the
CHARGING VOLTAGE
meter.
2.2.5.2 High Voltage Polarity (
+
or
-
) and
ON/OFF
select controls
This group of three interlocked, self-latching push buttons turns the
High Voltage Power Supply
ON
or
OFF
and determines the
polarity. The polarity buttons are dual function since they select the
polarity of the charging voltage and turn the High Voltage Power
Supply on. The HVPS is turned off by depressing the center
OFF
button. Since these three buttons are interlocked, depressing any
one button will release the one that was previously depressed.
Further, only one button should be depressed at a time.
2.2.6 CUTOFF Threshold Selection
2.2.6.1
Discharge
CUTOFF
select buttons
This group of three interlocked, self-latching buttons selects the
decay time measurement
CUTOFF
threshold. Three cutoff
thresholds are provided: 50% (Half Life), 10% (per NFPA 99), and
1% (per Mil-PRF-81705D, and EIA and ESD 541). These buttons
are interlocked; hence, depressing any one button will release the
one that had been previously depressed. Only one button should
be depressed at a time. If more than one button is depressed, an
error will result in the decay time measurement due to the
programming of a non-standard cutoff threshold. For those
applications where testing to CECC 00015 Section 8.2 is required,
the 50% cutoff is replaced by a 5% cutoff threshold and the full
scale
SAMPLE CHARGE
meter reading is changed to 1 kV.
