Specifications

Guide to Operation - Menus
26
The input to counter T can be the internal 10 MHz
timebase (rate measurement), the signal at INPUT
2 discriminated by T discriminator (ratio or
reciprocal measurement), or the TRIGGER input
discriminated by the trigger discriminator
(constant gate aperture). The selected counter
input can be viewed at the T DISC output. The
appropriate T counter source LED is lit.
If counter B is preset, this line is inactive
(indicated by the **** on the display). If counter T
is preset, both parameters on this line are active. T
SET is the preset value of counter T from 1E0 to
9E11. If the T input is 10 MHz, then T SET is
displayed as real time = T SET cycles of 10 MHz.
ChangingT SET during a scan causes the counters
to pause; any COUNT PERIOD in progress is
terminated and ignored. A START begins the next
COUNT PERIOD with the new preset value.
N PERIODS=2000 [at 1234]
This line programs the number of COUNT
PERIODS in one scan from 1 to 2000. N
PERIODS determines the length of the internal
data buffer and the range of any scanned
parameters. The quantity in brackets is the number
of completed COUNT PERIODS in the current
scan.
Changing N PERIODS during a scan changes the
length of the current scan. Reducing N PERIODS
past the current scan position will cause an end of
scan condition.
AT N= STOP DWELL= 1E0 s
START 2E-3 s
EXTERNAL
This line sets the end of scan mode and the
DWELL time. When a scan reaches N PERIODS,
the counters may be paused or restarted. AT
N=STOP causes an end of scan pause. All scanned
parameters are held at their final values. A counter
reset is required before another scan can begin. If
N PERIODS is 1, then each START results in one
COUNT PERIOD. If N PERIODS is greater than
1, then consecutive COUNT PERIODS are
separated by the DWELL time. During the
DWELL time, counting is disabled and scanned
parameters updated. The DWELL OUTPUT is
TTL high during the DWELL time.
If AT N=START, the counters will wait one
DWELL time at the end of each scan, during
which all scanned parameters return to their start
positions, and then another scan begins. This is
used for continuous data taking with the
measurement rate determined by the COUNT
PERIOD plus the DWELL TIME.
The DWELL time may be programmed from 2E-3
s to 6E1 s (1 minute) or set to EXTERNAL. The
internal DWELL time is based on the 10 MHz
timebase and may have 200 ns of indeterminacy.
Changing the DWELL time during a scan causes
the counters to pause; any COUNT PERIOD in
progress is terminated and ignored.
Setting the DWELL time below 2E-3 s results in
an EXTERNAL dwell. In this mode, the START
key, EXT START, or remote start command starts
the COUNT PERIOD. The COUNT PERIOD lasts
until the preset condition is reached. The following
DWELL time is indefinite; the next COUNT
PERIOD begins with another START. A STOP
key, EXT STOP, or remote stop command during
the COUNT PERIOD terminates the COUNT
PERIOD. Thus by programming the preset
COUNT PERIOD much longer than required, the
COUNT PERIOD may be determined by START
and STOP. Scanning proceeds as normal.
NOTE: If AT N=STOP, the counters will pause at
the end of a scan. A reset (STOP key, EXT STOP,
or remote reset command) is required to rearm the
counters before another scan can begin. In general,
to reset the counters at any time, the STOP key is
pressed twice in succession.
D/A= A
B
A+B
A-B
The D/A output is proportional to the count data
on the top line of the LCD. When the COUNT is
A-B, A+B, or A only, the D/A output can only
follow the data display. In these modes, the cursor
is inactive and the knob does nothing. If the