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3.
Description
The calibrator is based on a 1000 Hz stabilized oscillator which drives a
piezoelectric bender. This bender is coupled to a membrane which produces
a sound pressure in the coupler volume. As the system is adjusted to reso-
Fig.
3. 1.
Operation of 4230.
nate at 1000 Hz and is driven at this frequency, the equivalent volume is
very high. In order to avoid influence on the stiffness of the volume behind
the diaphragm caused by change in static pressure, a Helmholz-resonator
construction is made. (Fig.3.2)
A built-in temperature compensation ensures accurate calibration over the
whole temperature range of the calibrator.(Fig.3.3)
A
hold circuit is included to facilitate operation. This circuit holds the signal
8
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