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1.5 S/N Meter
The Ratio calculating method described in Section 1.3 can be used to
measure signal—to-noise ratios also.
The hold circuit in Fig.
1-2
retains the level of the signal,
which is divided by the noise level
(rms)
for direct reading of the S/N value.
The oscillator output of
the VF-7721A is suppressed during noise level measurement for use as a
signal source for S/N measurement.
The S/N indicator ranges can be switched automatically.
High—pass
filter and low-pass filters can be inserted in the circuit wherever
necessary.
The monitor output connector is used for noise component
analysis.
1.6 Pr e se tt ing
presetting is useful when specific settings are used repeatedly.
For
example, the following seven settings can be stored in register A-l and
can be recalled at a time simply by pressing keys A and 1.
(1)
Frequency
1 kHz
(2)
Output amplitude
0 dB
(3)
Measurement function
Distortion factor
(4)
Low-pass filter frequency
80 kHz
(5)
Range switching mode
Manual
(6)
Input level meter range
3V full scale
(7)
Indicator range
0.1% full scale
A maximum of sixteen similar setups can be stored and recalled.
Settings can be revised after they are recalled.
The additional sixteen
registers are provided for expansion up to 32 in remote-control
operation.
1.7 Remote Control
The VP-7721A has a remote control connector on the rear panel.
The
function includes a maximum of 32 front panel setups to be recalled,
modification with a rotary encoder, digital display selection,
and
■ H PF/LPF
on/off control.
■iM
O
CM
O
i
cn
oo
CD
1-4
rr
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