Uct's Using Print Hold Mode; Uct's Using Holcj/Reset Mode; Special Applications; Remote Display-Special Applications - Racal Instruments 9901 Maintenance Manual

Universal
Counter
Timers (UCT's) -
Basic
Hold Requirements
13.
The measurement cycle of the
99
series
of
UCT's
has
tv/o
distinct
phases; the
Gate Time
during
which
the
measurement
is
made, and the
Display
Time
during
which
the
results
are displayed.
If
the hold time required by
the
equipment
to
which
the interface
is
connected
is
less
than the display time, the remainder of the display
time
is
effectively wasted.
The
interface
can be
used
to
shorten the display time, but
in so
doing the
counter
display
is
reset,
which
may
not
be convenient.
For
this
reason the interface
can be used with
UCT's
in
two
modes, the Print
Hold and
the Hol4/Reset modes,
as
described
in
paras
14
and
15.
It
should
be noted that,
with
UCT's,
the interface
will
not
produce a data
change
or Print
Command
signal
from the operation of a
front
panel
RESET
control.
U
CT's Using Print
Hold
Mo
de
14.
In
the
Hold/Reset
mode
the Hold
signal
extends
the display time indefinitely the
next
gate time
commencing when
the Hold
is
released or
when
the
normal display period has
ended, whichever
period
is
the longer.
The Hold
signal
must be applied within the display
time period
in order to
halt the
measurement
cycle.
The required pin connections
on
the
50
way
connector
are
as
follows:-
Pin
No. Required
Connection
Pin 19
Connected
to Pin
50
(or to
5V
via 180C^
Pin
49
Connected
to
the
Hold
signal
source
Pin
24
To be open
circuit
or
connected
to
O/
UCT's
Using Hold/Reset
Mode
15.
In
the
Hold/Reset
mode
the
Hold
signal
(minimum width 5
ms)
extends the display time
indefinitely, but
when
it is
released the counter display
resets
and
a
new
measurement
commences.
This
result in
a more
rapid
measurement sequence, again
the
Hold
signal
must
be applied within the display time period
in
order
to
halt the
measurement cycle.
The
required pin
connections on
the
50-way
connector are
as follows:-
Pin
No.
Required
Connection
Pin 19
Connected
to
pin 50
(or to
5V
via 180C^
Pin
24 Connected
to
the
Hold
signal
source
Pin
49 To be open
circuit or
connected
to
OV
SPECIAL
APPLICATION
S
Remote
Display-Special Applications
16.
When
used
in the
unlatched
mode
with certain types of
equipment
other than remote
displays
(for
example a
digital
comparator) there
is
a limit to
the
maximum
possible
counting
rate.
Therefore
the reading
for
which
the
comparator
is
looking could
be
missed,
i
.e.
there
is
a
maximum
update
rate for
the option of
3-4
ms. This corresponds
to
an
input
frequency
of
200
Hz
(N=l) on
Totalize
mode
and
a
maximum
resolution
of
10ms on Time
Interval
mode.
The
counting
rate
can be
increased
if
a degree of overshoot can be
tolerated.
Section
4
:
99
Series
Appendix
1
.
Page App. 5