HP 400E Operating And Service Manual page 30

Section V Model 400E/EL
Paragraph 5-19 to 5-21
5-19. INPUT IMPEDANCE CHECK.
5-20. Input Resistance Check.
a. Connect the 50 Q output of the test oscillator to the input of the
400E/EL.
b. Set the test oscillator and the 400E/EL to the 3 volt range. Set
the oscillator output to 40 cps (Hz) and adjust the output for a full
scale indication as shown.
c. Connect a 100 K Q resistor between the test oscillator output and
the 400E/EL input as shown in Figure 5-2.
hp 400E/EL
TEST OSCILLATOR
AC VOLTMETER
hp 651A
1OOKN £19
O-< & On
400 /EL-8-0474 thee — 6|
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Figure 5-2. Input Impedance Check
d. The 400E/EL indication should not drop more than one small
scale division from full scale. This verifies an input resistance
of 10 M 2.
5-21. Input Capacity Check (Option 01, 02, and Standard 400E/EL).
a. Connect a test oscillator, a 100 K © resistor, and the 400E/EL
as shown in Figure 5-2.
b. With the 400E/EL on the 3 volt range, adjust the test oscillator
for a full scale reading on the 400E/EL at 400 cps (Hz).
c. Increase the test oscillator frequency until the 400E/EL indication
drops to 2.12 volts. This should occur at a frequency of 105 Kc
(KHz) or greater, verifying an input capacity of 9 pf or less on the
3 volt range.
d. Repeat steps a and b with the 400E/EL on the 1 volt range.
e. Increase the test oscillator frequency until the 400E/EL indication
drops to 0.707 volts. This should occur at a frequency of 55 Kc
(KHz) or greater, verifying an input capacity of 24 pf or less on
the 1 volt range.
5-8