Ratio; Ratio Measurement - Racal Instruments 9901 Maintenance Manual

RATIO
3.13
The
principle of
operation
is
very similar to
frequency measurement, except
that
the time base output
is
not
derived from the frequency standard.
Instead,
the
lower of the
frequencies to
be compared
is
applied to
the
'B'
Input
and divided
in
the time
base.
The
higher frequency
is
applied
to
the
'A'
Input
and fed via the
main
gate to the
counter.
A
waveform
from the
time base
decades
(derived from the
'B'
Input)
is
selected to
gate
the
'A'
channel signal
by
depressing
an appropriate
Range
('n')
push-button.
Since
the
time base output
is
a divided version of the
'B'
signal,
the readout gives
a count
which
corresponds to the ratio
of the
two
input frequencies, multiplied
by the factor
'n'
.
The
particular
'n'
factor
used
is
that
shown
adjacent to
the selected push-button.
SHAPER
Ratio
Measurement
Fig.
3.
5
3-6
9901 Vol.
2