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HEWLETT-PACKARD

JOURNAL
TECHNICAL INFORMATION FROM THE -hp- LABORATORIES
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Vol. 8 No. 5

iLISHED BY THE HEWLETT-PACKARD COMPANY, 275 PAGE MILL ROAD, PALO ALTO, CALIFORNIA JANUARY, 1957




An RC Oscillator that Covers the
20 cps-20 kc Range in a Single Dial Sweep
OVER a period of time -hp- has designed expense. In such applications the response of
resistance-capacity test oscillators for interest is plotted on the face of an oscilloscope
many fields of work from the sub-audio to the or on an X - Y recorder. To facilitate using
lower r-f ranges. The usefulness of this type motor drives, the new oscillator is arranged so
of instrument has now been even further ex that an extension of the tuning dial shaft is
panded in the form of a new RC oscillator that available at the rear of the cabinet.
covers the entire 20 cps - 20 kc range in a single Automatic measurements are further facili
dial sweep. This new test oscil tated by the fact that the dial calibration of
lator thus simplifies and speeds the new oscillator is essentially logarithmic.
testing of audio circuits and This factor is especially convenient for making
devices of many kinds. The response of ampli automatic response measurements in which
fiers, transformers, speakers and circuits can the response of the device under test is re
all be checked over the entire audio range by corded or viewed on an oscilloscope.
a single dial twist. In addition to the above features the oscil
Automatic response measurements can also lator retains the basic advantages such as high
be made with the new oscillator by equipping waveform purity, constancy of output over a
it with an external motor drive. Such an ar wide range, high stability, high calibration ac
rangement has proved valuable in both pro curacy, and freedom from zero setting that have
duction and laboratory applications where always been associated with -hp- oscillators.
performance information on audio devices is Fig. 1 is typical of the response informa
desired with maximum speed and minimum tion that can be obtained in only a few minutes




Fig. 1. Oscillogram of response of quality matching trans
former at