ACCEPTANCE TESTING
5-20
AF input tests
Audio frequency meter
This test confirms the accuracy of the audio counter hardware. Overall accuracy is governed by
the instrument reference frequency. The reference is checked independently elsewhere. Note: If
the LF generator is not available then the Audio generator frequency check will confirm that the
audio frequency meter is functional.
Specification
Frequency range:
20 Hz to 20 kHz
Resolution:
0.1 Hz, less than 10 kHz
1 Hz, at 10 kHz and above.
Accuracy:
As frequency standard ± digit ± resolution
Sensitivity:
50 mV
Test equipment
Description Minimum specification Example
LF generator 20 Hz to 20 kHz frequency external standard
In/Out
HP 3325B
DVM 1 % accuracy 20 Hz to 20 kHz Solatron 7150+
(1) Refer to Results table 5-25 on page 5-45. Connect the equipment as shown in Fig. 5-12
connecting to the UUT AF input socket. The frequency standards of the UUT and LF
generator should be locked together. The 50 Ω load is in circuit because the LF generator
used indicates level across 50 Ω.
(2) Press [HELP/SETUP], [Setup], [AF Filters], [Factory Preset], [Return], [Return], [Return].
Set the UUT to [AF TEST]. Press [AF Filter], [50kHz LP] to set the Audio Input filter to
50 kHz Low-pass.
(3) Set the DVM to monitor Volts AC.
(4) Set the LF generator to the first frequency shown in the Results table 5-25, and adjust the
level for an indication of 50 mV RMS on the DVM. Check that the frequency indicated on
the UUT audio counter is within the limits shown. Repeat for the remaining frequencies in
the table.
LF generator
C6049
DVM
AF INPUT
VOLTMETER
INPUT
TERMINALS
50
UUT
Fig. 5-12 Audio frequency meter check
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