TM 11-6625-2965-14&P
5-8 TEST EQUIPMENT REQUIRED
5-9 Table 5-1 lists the test equipment required
to perform the various procedures described in this
Section.
NOTE
A satisfactory substitute for a differ-
ential voltmeter is to arrange a refer-
ence voltage source and null detector
as shown in Figure 5-3. The refer-
ence voltage source is adjusted so
that the voltage difference between
the supply being measured and the
reference voltage will have the re-
quired resolution for the measurement
being made. The voltage difference
will be a function of the null detector
that is used. Examples of satisfacto-
ry null detectors are: 419A null
detector, a dc coupled oscilloscope
utilizing differential input, or a 50mV
meter movement with a 100 division
scale. For the latter, a 2mV change in
voltage will result in a meter deflec-
tion of four divisions.
TYPE
Differential
Voltmeter
Variable
Voltage
AC Voltmeter
Oscilloscope
Oscillator
DC Voltmeter
Repetitive
Load Switch
Figure 5-3. Differential Voltmeter Substitute,
Test Setup
CAUTION
Care must be exercised when using an
electronic null detector in which one
input terminal is grounded to avoid
ground loops and circulating currents.
Table 5-1.
Test Equipment Required
REQUIRED
CHARACTERISTICS
Sensitivity: lmV full scale
(min.). Input impedance:
10 megohms (min.).
Range: 90-130 Volts
Equipped with voltmeter ac-
curate within 1 Volt.
Accuracy: 2%. Sensitivity:
lmV full scale deflection
(min.).
Sensitivity: 10µV/cm. Differ-
ential input.
Range: 5Hz to 600kHz
Accuracy: 2%
Accuracy: 1%. Input resist-
ance: 20,000 ohms/Volt (min.).
Rate: 60-400 Hz, 2µsec rise
and fall time.
USE
Measure dc voltages;
calibration procedures
Vary ac input
Measure ac voltage and
ripple
Display transient response
waveforms
Impedance Checks
Measure dc voltages
Measure transient response
RECOMMENDED
MODEL
3420 (See Note)
403 B
140 A plus
1402A plug in.
200 CD
412A
See Figure 5-6
5-2
