Racal Instruments 9916 - Page 82

Universal Counter Timers (UCTl
s
)
:- Basic Hold Requirements
13. The measurement cycle of the 99 series of UCT's has two distinct phasesi the Cate 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 ~he 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 Hold/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. .
UCT1s Using Print Hold Mode
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.
Pin 19
Pin 49
Pin
24
Regui red Connection
Connected to Pin 50 (or to 5V via 1800)
Connected ro the Hol d si gnal source
To be open circuir or connected to 0/
UCT's Using Hold/Reset Mode
15. In the Hold/Reset mode the Hold signal (r.1inimum 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 os follows:-
Pin No.
Pin 19
Pin
24
Pin 49
Required Connection
Connected to pi n 50 (or to 5V vi a 1800)
Connected to the Hold signal source
To be open ci rcui t or connected to OV
,
"
SPECIAL APPLICATIONS
Remote Display-Special Appl ications
16. When used in the unlakhed mode with certain types of equipment other ~han remote
displays (for example a digital comparator) rhere 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 op~ion 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