Delta OHM HD2024, Руководство по эксплуатации

Страница: 7 / 14

HD2024
- 7 -
V1.0
5 CONSTRUCTION AND FUNCTIONING
Calibrator mechanical construction (section)
The figure schematizes the HD2024 calibrator structure (in section). The battery com-
partment is on the right side of the case. The printed circuits with the electronics are
over and under the battery compartment. The electro-acoustic transduction system is
on the left and it consists of a wide cavity with a piezoceramic generator and a feed-
back sensor. The system emits the signal through the 1/2” microphone cavity. An
outer capillary hole balances the chamber static pressure protecting microphones from
overpressure due to their insertion.
The electronics consist mainly of an oscillator combining high stability and low distor-
tion, as well as an RMS converter, the automatic gain control (AGC), the driver for the
ceramic resonator and the electronics for conditioning the signal from the feedback
sensor.
The RMS level of the signal provided by the sensor is compared with the factory set
reference level; the difference adjusts the width, through the automatic gain control,
of the signal generated by the oscillator and thus the acoustic signal generated by the
piezoelectric transducer.
The signal provided by the sensor has minimal changes with the ambient temperature
and the static pressure; the frequency of the signal provided by the oscillator is also
stable in relation to ambient parameters.