15
especially if a digital storage oscilloscope is used, causing significant
measurement error. This condition normally occurs when buried metal
layer bags are tested and 5, 10 or 20 Volt sensitivity levels are selected to
obtain greater voltage differential resolution. To verify the signals, switch
out of the ADD mode and into the CHOP mode and observe the individual
CH-1 and CH-2 signals.
d. Set the trigger to NORM and CH-1 trigger source. Adjust the level for
consistent triggering.
6.0 OPERATION
6.1 Discharge Waveform Verification
6.1.1 ANSI/ESD STM11.31 Energy
ANSI/ESD STM11.31 defines the discharge waveform, but EIA 541 does
not, however, both tests utilize a similar discharge pulse. Therefore,
following the ANSI/ESD STM11.31 verification procedure will also apply
to EIA 541 testing.
However, since the Model 4431-AV does not
include the CT-1 this measurement must be performed externally.
ANSI/ESD STM11.31 requires verification of the discharge current pulse
both through a short to ground and through a 500 Ohm resistor. This
requirement is based on an assembled apparatus where the Discharge
Simulator and the electrode assemblies are separate components. The
Model 4431-EV is an integrated system where the discharge waveform at
the discharge electrode is designed to meet the specified requirement.
Prior to each test in the AUTO mode the waveform, energy and peak
current is automatically verified. For verification testing before each test
series, measurement of the waveform with the capacitive sensor through
the CT-1 and the 500 Ohm resistor is required. This measurement is
performed by simply discharging directly to the capacitive sensor without
a sample in place. This waveform is shown in Figure 6.0-1 and should
measure between 420 and 500 milliamps and have an energy of 50,000
r
3,000 nanoJoules at a 1,000 Volt discharge.
To measure the actual discharge waveform from the discharge output
without the 500 Ohm resistor and capacitive sensor a separate CT-1
current transducer is required. Place the Calibration Wire supplied
between the discharge electrode and capacitive sensor upper electrode
with the white insulator against the upper electrode. Lock in place using
the lever. Feed the bare end through the CT-1. Insert the wire into the
ground point as shown in Figure 6.0-1. The Discharge waveform per
ANSI/ESD STM 5.1 can now be measured.
