Svantek SV 35A User Manual - page 3
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SV 35A User Manual
1. Introduction
One of the fundamental questions that are most frequently asked while taking
a measurement is whether its result is accurate. Proceeding with a measurement without
having a positive answer to this question may result in obtaining data of
no practical use and wasting our time. However, we may easily obtain the answer
by performing a calibration of the sound level meter together with the microphone and its
preamplifier. Calibration of the measurement device may be done in two ways: by comparing
the calibrated device with a reference device of known parameters; or using a template of the
measured quantity to perform a reference measurement. Acoustic devices are usually
calibrated in the latter fashion with so-called, acoustic calibrators. Acoustic calibrator is a
device, which produces acoustic pressure of defined level and frequency. In other words, such
calibrator is a reference of acoustic pressure. With help of such a reference we can check the
accuracy of the measurements performed with the sound level meter and/or calibrate it if the
error occurs.
2. Acoustic calibrator SV 35A
2.1. General description
The SV 35A acoustic calibrator is a small, portable dual-range Class 1 device (sound
source), see Picture 1. Powered by two LR03/AAA batteries, it contains
a loudspeaker producing acoustic pressure, reference microphone for monitoring generated
level, pressure and temperature sensors for measurements of atmospheric conditions and a
microprocessor system controlling the operation of the calibrator. Sinusoidal waveform of
1 kHz frequency is digitally generated and feeds the loudspeaker. Sampled signal from the
reference microphone indicates the level of currently generated signal in a feedback loop. On
the basis of information about the level of the signal, actual values of pressure and
temperature, microprocessor adjusts amplification of the loudspeaker signal in order to
produce appropriate sound pressure level in the calibrator’s chamber.
Due to the feedback regulation loop the SV 35A calibrator does not require adjusting and
operates in a wide range of temperatures and humidity (see SV 35A Datasheet).
Picture 1. Acoustic calibrator SV 35A