Page 2 - 1961 , Volume v.12 n.9 , Issue May-1961

FREQUENCY was previously equal to the gate
COUNTING time, the interval between gate
10 SEC times in the new counters can be
G A T E x G A T E A P E R - 1 0 P E R C O O P E R
considerably shorter. Thus, for the
longer count times of 1 and 10 sec
onds, the new counters can operate
at nearly double the previous maxi
mum sampling rates if the minimum
display time is used. The between-
count interval can be adjusted by a
panel control up to 5 seconds, and an
infinite display position is also pro
vided.
INCREASED-ACCURACY
PERIOD MEASUREMENTS
Each of the new counters is cap
10 KC - 1 MC able of making multiple-period
FREQUENCY average measurements up to 10s
Fig. 2. 1.2-mega- relating period- and frequency-measuring accuracy of new 1.2-mega- periods. For low and mid-range fre
cycle counter. Frequencies for which counter will give better accuracy on period
measurements than on direct-frequency measurements is shown by solid portion of quencies the periods-average tech
curves. Curves assume time base error of 1 X 10~6 and trigger error of 03%/number nique can greatly increase measure
of periods averaged. Using external time base, accuracies of 1 X. 10~s can be achieved ment resolution and accuracy over
with 1 0s period measurements.
that possible with direct-frequency
in a storage flip-flop to control the Since the time available for read counting. Consider, for example,
display. This feature together with out with storage includes the gate measuring a 400-cps sine wave, first
the code conversion from binary- time, sample rate is no longer lim by direct frequency -counting and
coded decimal to decimal output at ited by the need to provide enough then by period and multiple-period
the high voltage required for indi time between counts for a readable average measurement with the new
cator tubes is achieved by the use of display. Thus more readings per sec 1.2-megacycle counter. Since in the
a special photoconductor matrix de ond can be obtained. period measurement modes he
t
veloped at -hp-. In decoding alone Another improvement has to do counter is gating a 1-mc count fre
this single solid-state matrix replaces with the interval between counting quency, each period of the 400-cps
many semiconductor elements per times— usually called "display time". input signal results in 2500 counts
decade. Where the minimum display time being registered. In the 1000-period

4 6 8 1 0 1 2 1 4 1 6 1 8
D A Y S
Fig. operating Long-term accuracy curve measured of achieved by operating time-base crystal near room
time base in 1.2-megacycle counter. Excellent long- temperature. Short-term variations in curve are
term stability for a counter of this class has been largely due to ambient temperature variations.

1 4 1 6 28
DAYS
Fig. 300-kilocycle Long-term accuracy curve measured of time-base in 300-kilocycle counter.

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