407744 Datasheet, PDF (3/4 Pages) Extech Instruments Corporation. – Sound Level Calibrators

Description
Note that only the 407766 is pictured.
1. ½” Microphone adaptor *
2. 407766: OFF-94dB-114dB switch
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407744: OFF-BATTERY TEST-94dB switch
3. 407766: POWER-ON / LOW-BATTERY status LED
407744: BATTERY OK LED
4. Battery compartment cap
* To remove the ½” adaptor, pull straight down
as shown in diagram below.
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Operation
Theory of Operation
The 407744 sound level calibrator generates a 94dB sine wave at 1 KHz. The 407766
generates a 94dB and a 114dB sine wave at 1kHz. When a microphone from a sound level
meter is inserted into the calibrator, the sound level meter picks up the signal and displays
the signal in dB (decibel) units. The sound level meter should be adjusted (if necessary) to
match the calibrator’s output signal as closely as possible (see diagram).
Procedure
1. Insert the microphone into the calibrator’s microphone cavity as shown; ensure that it is
fully inserted. Use the ½” microphone adaptor (supplied attached to
the calibrator) for ½” microphones. Remove the adaptor (remove as
shown in the Description section) for 1” microphones.
2. On the 407744, slide the function switch to the ‘I’ (Power On) position.
As soon as the unit is powered, the calibration tone is generated. On
the 407766, slide the function switch to the 94dB or the 114dB
position as desired. The calibrator generates its signal as soon as the
switch is set.
3. Read the sound level meter’s display. The sound level meter should
read 94dB or 114dB depending on the calibrator’s setting. If the sound
level meter does not match the calibrator’s signal (within
specification), adjust it as explained in the Operation section (typically
a front or side-panel pot adjustment). Refer to diagram at right.
4. Slide function switch to the OFF position, and remove the microphone.
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Models 407744 & 407766 - Version 5.0 - May 2005