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HEWLETT-PACKARD
JOURNAL
TECHNICAL INFORMATION FROM THE -hp- LABORATORIES
Vol. 5 No. 3-4
1LISHED BY THE HEWLETT-PACKARD COMPANY, 395 PAGE MILL ROAD, PALO ALTO, CALIFORNIA NOV.-DEC, 1953
A New 60 -Cycle Per Revolution Generator
for Precision Tachometry Measurements
'"T~1HE new -hp- Model 5 08 A Tachometer in one of its major applications: quick pro
_L Generator is designed to be used with duction-line checking of slip in electric mo
the -hp- Model 522 Electronic Counter to tors. The generator output terminal is con
make rapid, high-precision measurements nected to the 522 counter, which is set for a
of rotary speeds. For each revolution of its 1 -second frequency measurement1. The gen
driving shaft, the generator provides 60 erator shaft is connected to the shaft of the
cycles of output voltage. This speed multi production motor, either directly or through
plication feature enables a test load or similar arrangement. The
SEE ALSO:
"Time-Frequency the combination of counter then automatically displays in digi
Transform Table"
on inside pages
counter and generator to tal form the rpm of the motor. A panel con
make in 1 second preci- trol on the counter allows the operator to
sion tachometry measurements that are di select the length of time that the counter
rect-reading in revolutions per minute. The displays its measurement. At the end of this
speed and accuracy obtainable with the gen time the counter automatically repeats its
erator and counter also make them valuable measurement which requires 1 second. Meas
for a number of other studies of mechanical urements can thus be made as often as de
motion besides simple measurements of rpm. sired.
Fig. 2 indicates how the generator is used Rpm measurements made with the gener
ator and counter are made to a high order of
accuracy: within ±1 rpm2. If higher accu
racy is desired, the measurement can be
made for a 10-second instead of 1 -second in
terval, in which case an accuracy of ±0.1
rpm ±0.001% is obtained. These accuracies
are achieved even by non-technical person
nel, because the -hp- 522 presents the meas
ured speed in digital form and because no
operating adjustments are necessary.
Basically, the generator consists of an al-
nico magnet arranged in a closed magnetic
loop which is interrupted when the genera
tor shaft is turned. A pick-up coil couples
the induced voltage to a coaxial type output
connector. The closed-loop design enables
(Continued on back page)
Fig. 1. New -hp- Model 508A Tachometer Generator 'The the 522 Electronic Counter measures frequency by counting the
number of cycles of the signal voltage that occur in an accurately-
produces 60 cycles of railage for each revolution of its determined time interval such as 0.1, 1, or 10 seconds. See Hewlett-
shaft. When used with the -hp- 522 Electronic Counter, Packard Journal, Vol. 4, No. 3, and Vol. 5, No. 1-2. Copies avail
precision rpm measurements can be made in 1 second. able on request.
2This neglects the 522 gate-time inaccuracy which is insignificant at
A 100-cycle model is also available. all but the highest rpm's.
P R I N T E D I N U . S . A . C O P Y R I G H T 1 9 5 3 H E W L E T T - P A C K A R D C O .