Norsonic nor1256, Instruction Manual

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1 Nor1256
Instruction Manual
Introduction
The Sound Calibrator Nor1256 is a small, battery
operated sound source for the calibration and check
of sound measuring instruments. The specifications
conform to the requirements in IEC 60942 for a class
1 sound calibrator. The combination of two different
levels and two different frequencies allows both level
linearity and frequency linearity to be verified. In addi-
tion the Sound calibrator measures the environmental
conditions: air pressure, temperature and humidity.
The sound calibrator may be used for calibration
and check of most laboratory and working standard
microphones with diameter not larger than 1” (LS1/
WS1).
The microphone of the sound level meter shall
be placed in the acoustic coupler of the calibrator
before the calibrator is switched ON. After start up the
calibrator will produces a regulated sinusoidal sound
pressure signal at 1 kHz with a sound pressure level
of 94,0 dB. The sound is generated by a small loud-
speaker integrated in the acoustic coupler. The level is
measured with an internal reference microphone and
is automatically adjusted until the level is correct. This
is indicated by the LED on the front turning from red
to green. The feedback ensures that the sound level is
nearly independent of the acoustic load volume of the
microphone.
By pressing the dB button, the sound pressure level
may be switched between 94 dB 114 dB.
By pressing the Hz button, the frequency of the
sound may be switched between 1 kHz and 250 Hz.
Due to the principle of operation, the calibration level
is virtually independent of ambient conditions like tem-
perature, atmospheric pressure and humidity within
the specified range of operation.
The calibrator has been designed to serve one-
inch and smaller microphones and sound level
meters equipped with such microphones. One-inch
microphones fit directly in the calibrator coupler, while
half-inch and smaller microphones are served by
application of a suitable adaptor. Adaptor for half-inch
microphones is included, while adaptors for other
microphone sizes must be ordered separately.
The calibrator is powered from two type LR03
alkaline batteries (AAA-size, also classified as 24A by
ANSI/NEDA). If the voltage is too low to ensure proper
operation, the calibrator will switch off or not switch on.
Remove the batteries as soon as they are discharged
or if the sound calibrator is stored for a prolonged
period of time. Leakage from the battery may other-
wise destroy the electronic components.