Extech Instruments 407744 User manual

User’s Manual
Model 407744 and 407766
Sound Level Calibrators
Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176
FAX [phone] - TestEquipmentDepot.com
99 Washington Street
Melrose, MA 02176
Phone [phone]
Toll Free 1-800-517-8431
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Page 2 Models 407744 & 407766 - Version 5.0 - May2005
Introduction
Congratulations on your purchase of Extech’s Sound Level Calibrator. Extech Calibrators
accommodate Sound Level Meters with 0.5” and 1” microphones. The Calibrator’s die-cast
aluminum housing is built for ruggedness and durability. The 407744 provides a 94dB
calibration output signal while the 407766 provides both 94dB and 114dB outputs. This
professional calibrator, with proper care, will provide years of safe reliable service.
Specifications
Output signals 407744: 94dB
407766: 94dB and 114dB
Output signal accuracy 407744: ± 0.5dB;
407766: ± 0.5dB (94dB), ±0.8dB (114dB)
Output signal frequency 1KHz sine wave
Accuracy of output signal frequency ± 5%
Compatible microphones sizes 0.5” and 1” microphones
Total Harmonic Distortion (THD) <2%@94dB, <5%@114dB (407766)
Operating temperature 32 to 122oF (0 to 50oC)
Power supply Two (2) 9V batteries
Power consumption Approx. 10mA DC
Battery check Status LED
Dimensions 2.2” diameter x 5.7” length (50 x 145mm)
Weight 0.75 lbs. (340g)

Page 3 Models 407744 & 407766 - Version 5.0 - May2005
Description
Note that only the 407766 is pictured.
1. ½” Microphone adaptor *
2. 407766: OFF-94dB-114dB switch
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.
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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Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176
FAX [phone] - TestEquipmentDepot.com