HP 4262A Operating And Service Manual page 40

Model 4262A
3-19. D/Q Blanking Function
{Switch selectable function inside cabinet).
3-20. The D/Q blanking function permits deac-
tivating the D/Q measurement as desired. If op-
erator has no need of D/Q measurement data, and
alternatively desires to make higher speed LCR
measurements, the switch for this function may be
set. When the D/Q function is deactivated, meas-
urement time is shortened to approximately 220 to
250 milliseconds (at 120Hz) and to 80 to 110
milliseconds (at 1kHz and 10kHz) as compared to
standard measuring times (which includes a D/Q
measurement). The D/Q deactivating switch is
located on the A23 board assembly. To select this
function, change setting of the switch as follows:
a. Remove top cover.
b. Take out A23 board (red and orange colored
extractors).
¢. The selection switch is mounted near left
edge of the A23 board.
d. Change position of the switch as illustrated
below.
e. Reinstall the A23 board in its normal position,
f. Replace top cover.
normal D/Q blanking
HPIB | fir_—1- HPIB | m—-
cMmp |, I~ CMP | 1~
BCD
|7 M«
BCD
|7 @M«
LCR | - LCR l C_1m -~
3-21. General Component Measurement.
3-22. Figure 3-7 shows the operating procedures
for measuring an L, C or R (inductance, capaci-
tance or resistance) circuit component. Almost all
discrete circuit components (inductors, capacitors
or resistors )except for components having special
shapes or dimensions can be measured with this
setup. Special components may be measured by
using Test Leads 16062A or 16063A or by
specially designed user built fixtures instead of
16061A Test Fixture.
Section III
Paragraphs 3-19 to 3-29
3-23. Semiconductor Device Measurement.
3-24. The procedures for using the 4262A semi-
conductor device measurement capabilities are des-
cribed in Figure 3-8. For example, the junction
(interterminal) capacitance of diodes, collector
output capacitance of transistors, etc., can easily
and accurately be measured (with and without dc
bias).
3-25. External DC Bias.
3-26. A special biasing circuit using external volt-
age or current bias, as needed for capacitor or in-
ductor measurements, is illustrated in Figure 3-9.
The figure shows sample circuitry appropriate to
4262A applications. Biasing circuits must avoid
permitting dc current to flow into the 4262A as dc
current increases the measurement error and
the excess current sometimes may cause damage to
the instrument. When applying a dc voltage to
capacitors, be sure applied voltage does not exceed
maximum working voltage and that you are observ-
ing polarity of capacitor. Note that the external
bias voltage is present at Hcur and Heor terminals.
3-27. Bias Voltage Settling Time. When a meas-
urement with dc bias voltage superposed is per-
formed, it takes some time for voltage across
sample to reach a certain percentage of applied
(desired) voltage. Figure 3-9 shows time for dc
bias voltage to reach more than 99% of applied
voltage and for 4262A to display a stable value. If
the bias voltage across sample is not given suffi-
cient time to settle, the displayed value may
fluctuate or O-F may be displayed. Read measured
value after display settles.
3-28. External Triggering.
3-29. For triggering the 4262A externally, connect
an external triggering device to the rear panel EXT
TRIGGER connector (BNC type) and press EXT
TRIGGER button. The 4262A can be triggered by
a TTL level signal that changes from low (0V) to
high level (+5V). Triggering can be also done by
alternately shorting and opening the center con-
ductor of the EXT TRIGGER connector to ground
(chassis).
Note
The center conductor of the EXT
TRIGGER connector is normally at
high level (no input).
3-9