14. Class 1 high pressure Pistonphone - 42AC

The 42AC is an extremely stable laboratory standard sound source which can also be used for field calibrations – it retains its high accuracy even under hostile environmental conditions. 

More details

Typical applications and use

- Reference sound source

- Precision microphone calibrations

- Microphone comparisons

- Precision hydrophone calibrations

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Design

With a microphone placed in the coupler of the pistonphone, the calibration level is:

-134 dB 1 re. 20 μPa
-125.4 dBA re. 20 μPa (with A-weighting applied)

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The 42AC is an extremely stable laboratory standard sound source which can also be used for field calibrations – it retains its high accuracy even under hostile environmental conditions. At a static ambient pressure of 101.3 kPa, no further correction factors need be applied.

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The 42AC complies with all the requirements of IEC Standard 942 (1988) Sound Calibrators Class 1 when corrected with barometer ZC0003K (included). The 42AC is delivered with a ½" coupler (RA0048) for calibrating ½" microphones directly. The 42AC-S2 is a version of the 42AC that is delivered with a 1" coupler (RA0023) for calibrating 1" microphones directly.

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The pistonphone works on the principle of four reciprocating pistons actuated by a precision machined cam with a sinusoidal profile. The rotation speed of the cam is controlled to within 0.5% via a tachometer signal in a feed-back loop.

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The 42AC has a dual-colour LED above the ON/OFF switch to indicate both battery condition and stable operation. When the pistonphone is operating properly, the LED shows green, indicating that the speed of the cam is correctly locked to give 250 Hz. If it shows red while the pistonphone is switched on, the speed is incorrect; most likely because of low batteries.

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The Pistonphone 42AC is compatible with G.R.A.S. ½", ¼", and ⅛" microphones and all other microphones having the same standard diameters. Adapters are included for calibrating ¼" and ⅛" microphones. Where applicable, the coupler RA0023 is also available for calibrating 1" microphones.

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Sound Pressure level : 134dB

Frequency : 250Hz

ANSI:  S1.40

IEC: 60942

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