Frequency Meters - Special Applications - Racal Instruments 9901 Maintenance Manual

The
maximum
overshoot
that will
occur
is
given by:-
-3
Counting Rate
x
4
x 10
counts.
It
is
advisable to use the Print
Command
as
a
'data valid' signal in
such
systems.
Frequency Meters
-
Special Applications
17. In
some applications
it is
not possible
to
use the interface in the
manner
described
in
Para 12. For
example,
in
control systems,
where the output
of the interface
is
used
as
feedback
to
the
device on
the input of the counter,
problems
arise
because the
next gate
time has already
started
before the information
becomes
available from the previous
one.
Therefore,
even
if
the
feedback correction
is
made
almost
instantly,
the
reading at the
end
of the
next gate time
will
be
incorrect.
Alternatively,
if
the correction process takes
more
than one
gate time, the
end
of gate time immediately following the process
will
also
give
incorrect
results.
These problems
may
be
overcome by applying a Hold
signal to
the Print
Hold input (pin 49)
for
the length of time
that the
correction takes, plus
an additional time
to
ensure that the
gate time from
which
the
next data
is
to
be
taken cannot
start
until the
correction process has
been completed,
as
shown
in Fig.
A3.
Fig.
A3
Section
4
:
99
Series
Appendix
1
.
Page App.
6.