Page 3 - 1961 , Volume v.12 n.9 , Issue May-1961

NEON OR IN-LINE INDICATORS

0 1 2 3 ) ( 4 H 5 ) ( 6 ) ( 7 K 8 H 9

INPUT

NPuHt Fig. 5. Counter assembly corresponding to circuit
shown in Fig. 4. Photoconductive matrix on small plate
in front fits inside assembly and greatly simplifies circuitry
Fig. 4. Basic circuit arrangement used to obtain con
tinuous readout feature. needed to achieve decoding and other circuit features.
average position, however, 2.5 x It is important to note that the gates to storage flip-flops which, in
106 counts are taken in 2% seconds, time base oscillators of the new turn, control the displayed readout
and measurement resolution is sev counters achieve this high stability through the decoding matrix. When
eral hundred times greater than in without the use of an oven. Besides a count is completed, the transfer
the direct frequency mode where the significant savings in terms of gate opens and the information pres
the longest gate time of 10 seconds space and power requirements for ent in the count flip-flops is trans
permits a total of only 4000 counts. the instruments, the following func ferred to the display, where it is
In addition to storage and mul tional advantages result: stored until the completion of the
tiple-period average, other unusual First, no warmup time is required. next count. In the meantime, the
features which add to the versatility The first readings obtained on the transfer gate has closed, allowing
of these instruments are binary- counter after turn-on meet the full the counting flip-flops to accumu
coded decimal output, wide operat specified accuracy. Secondly, high late new information without dis
ing emperature ange, and ad long-term stability is achieved. The turbing the displayed reading. Dis
r
t
vanced mechanical construction. aging rate of a crystal at or near play storage is thus achieved and
Four-line BCD output, suitable for room temperature is considerably reading changes occur only when the
systems use or direct measurement less than that of a crystal at the usual storage flip-flops are presented with
recording, is a standard feature on elevated oven temperature. See Fig. information different from the pre
the new counters. The code is 1-2-2-4. 3. Close control over the angle of vious count.
It is available through a rear con cut of quartz crystals results in a
PHOTOCONDUCTIVE
nector along with print-command minimum frequency change over a D E C O D I N G M A T R I X
and hold-off circuit access. wide temperature range. These crys The fact that it has been possible
The operating ambient tempera tals are a product of the Hewlett- to incorporate such features as dis
ture range over which counter per Packard Precision Components play storage without excessive cost
formance is specified is — 20°C to Division. or circuit complexity arises from the
-)-65°C. Over this range the time development and use of decoding
base frequency remains constant DISPLAY STORAGE matrices composed of simple photo-
within ±100 parts in 106 for the The functional block diagram of conductive elements. Each display
lower-frequency counter and within Fig. 4 illustrates how display storage decade includes an hermetically-
±20 parts in 106 for the higher-fre is accomplished. The counting flip- sealed unit containing special neon
quency counter. Over narrower tem flops are driven in the ordinary man lamps and a matrix composed of a
perature ranges, of course, the time ner by pulses from the trigger unit. photoconductive film in a suitable
bases remain within much narrower The outputs of these flip-flops are pattern. This unit replaces many
limits than these. then coupled through diode transfer semiconductor elements otherwise

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