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HEWLETT-PACKARD


JOURNAL
T E C H N I C A L

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I N F O R M A T I O N F R O M T H E - h p - L A B O R A T O R I E S Vol.6 No. 11

DISHED BY THE HEWLETT-PACKARD COMPANY, 275 PAGE MILL ROAD, PALO ALTO, CALIFORNIA JULY, 1955



A New 120 KC Industrial Counter for Measuring
RPM, Velocity, Quantity, Flow, Etc.
REQUENC Y counters are being used fixed sampling times. In addition, a panel
more and more for making the precision jack is provided to permit the sampling time
measurements important in industrial work. to be controlled by an external switch or
Such measurements include the rpm of all relay.
sorts of rotating devices, measurements of The new counter makes two types of meas
velocity, length, pressure, etc. urements. First it will count externally-ap
A compact new frequency counter has plied electrical events for an interval of
been developed especially for such industrial 1/10 or 1 second as desired. The quantity it
applications. This new instrument counts displays is thus equal to events per tenth sec
frequencies or electrical events up to a maxi ond or per second. Second, if the manual
mum rate of 120,000 per second. It is thus start-stop (gate) switch is used, the counter
capable of counting the rpm of even the fast will totalize indefinitely as determined by
est rotating devices. It is provided with a dis the switch instead of for a fixed interval. Or,
play capacity of 9,999 counts and with sam if the panel jack is used with suitable exter
pling times of 1/10 or 1 second which are nal contacts, the counter can be used, for ex
selectable by the operator. A panel switch ample, to count the number of drum revolu
further adds to the flexibility of the instru tions for a given rise in brake temperature
ment by enabling the operator to start and under various load conditions, or for many
stop a measurement manually in place of the other applications where rotation as a func
tion of some dependent quantity is desired.
CIRCUIT
The basic arrangement of the counter is
shown in Fig. 2. The frequency to be meas
ured is applied to a gate circuit whose open
ing and closing is controlled either by an in
ternal time base circuit or externally. When
the gate is open, the signal passes through
and drives a series of four decade counters
which totalize the number of cycles applied
to them. A display time circuit enables the
operator to adjust the time that the count is
displayed after the measurement is made
from 1 10 to 15 seconds before the counter
automatically makes the next measurement.
Fig. 1. New -hp- Model 52! A Industrial Electronic Coun Display time can also be held indefinitely if
ter measures frequencies up to 1 20,000 cycles per second.
Internal time base system can be operated from power desired.
line frequency, from optional precision oscillator, or from
existing standard frequencies. If it is desired to operate the opening and

P R I N T E D I N U S . A . C O P Y R I G H T 1 9 5 5 H E W L E T T - P A C K A R D C O .