Scientific 5000 Series, Manual, Page: 243 / 360

APPENDIX A
MODEL 5000 SERIES MANUAL
Version 1.23
13-3
Appendix A
Oscilloscope
Guidelines
A scope can be used to observe applied device voltage waveforms. In general, a
scope probe can be attached to any of the three device leads (A, G or K) since the
return current monitor from the Hi Source Board flows through the emitter to the
monitor resistor bank. Never attach the scope ground to the emitter or any of the
other device leads.
Anode Monitor
Attach the scope probe to A
S
. Either leave the scope ungrounded or attach the
scope ground to the front panel jack labeled GND. Attaching the probe will not affect
test measurements.
A
S
to K
S
Monitor
For breakdown, leakage, h
FE
and other tests where a voltage of several volts or more
is applied to the anode, observation at the anode is representative of the voltage
from A
S
to K
S
because the voltage at the K
S
terminal is usually less than one volt.
For high current on-state tests where the expected A
S
to K
S
voltage is low, accurate
observation of the waveform can be obtained by using two scope probes and
subtracting the two traces to produce a differential display.
G
S
Monitor
The G
S
terminal can be similarly monitored. Be aware, however, that measurements
can be affected when the probe is attached because the gate is monitored ahead of
application to the gate. If, for example, 10 volts is applied to the gate and a 10 M
Ω
scope probe is attached, an error of approximately 1
μA will result.
Caution: Do not attach the scope ground to A, A
S
, G,
G
S
, K or K
S
terminals, the preferred location is chassis
ground.