Extech 407738 Operating Manual
User's Guide
Digital Sound Level Meter
Model 407738
Introduction
Congratulations on your purchase of the Extech 407738 Digital Sound Level Meter.
The 407738 measures and displays sound pressure levels in dB (decibels) from 26 to
130dB in six measurement ranges. The microphone can be removed and remotely
stationed for convenience. In addition to the LCD numerical displays, a bargraph is
included for quick and easy viewing of sound level changes. Features include selectable
Frequency Weighting (‘A’ and ‘C’), selectable Response Time (Fast and Slow), Max
Hold, and a 99 reading storage utility.
Careful use of this meter will provide years of reliable service.
With Memory
Specifications
Applicable Standards IEC61672-1: 2002 Class 2; IEC60651: 1979 Type 2; ANSI S1.4:1983 Type 2
Measurement Functions
Primary Functions Sound Pressure Level
Maximum Sound Level
Minimum Sound Level
Total range 26 to 130dB (32 to 130dB for ‘C’ weighted measurements)
Maximum level 130dB
Accuracy ± 1.5dB (under reference conditions)
Noise floor ‘A’ weighting: 26dB
‘C’ weighting: 32dB
Calibration signal 94dB at 1kHz (sinusoidal)
Range selections 26 to 80, 30 to 90, 40 to 100, 50 to 110, 60 to 120, 70 to 130
Frequency range 31.5 to 8000 Hz
Frequency weighting ‘A’ and ‘C’
Time weighting Fast (125ms) and Slow (1 second) Response
Calibration Requires external calibrator (not included)
Display update rate Bargraph display: 125ms; Numerical indication: 1 second
minimum sound level (Lmin) can be stored with elapsed timer.
Microphone 0.5” electret condensor
Display
Display features 4-digit indication of sound level with 0.1dB resolution
Bargraph indication of sound level with 1dB resolution
Elapsed time; 100 hours maximum
Store and recall readings (99 data sets max.)
Warning indicators Over-range ‘OV’; Under-range: ‘Un’
Analog Outputs AC: 0.707Vrms full scale; Output impedance: 5KΩ
DC: 10mV/1dB; Output impedance: 5KΩ
Power requirements 9V Battery; Battery life approx. 50 hours
Operating conditions 14 to 122
Storage conditions 14 to 132
Dimensions 10.4 x 2.7 x 1.1” (264 x 68 x 27mm)
Weight 9.2 oz. (260g)
Technical support: Extension 200; E-mail: support@extech.com
Repair & Returns: Extension 210; E-mail: repair@extech.com
Product specifications subject to change without notice
For the latest version of this User’s Guide, Software updates, and other
up-to-the-minute product information, visit our website: www.extech.com
Support line (781) 890-7440
o
F (-10 to 50oC); 90% relative humidity max.
o
F (-10 to 60oC); 90% relative humidity max.
Model 407738 Version 2.2 September 2005 2
Meter Description
1. Microphone: Electret condenser
2. Microphone collar: unscrew to remove microphone
3. LCD Display
4. Push-buttons:
• Power button
• A,C buttons: Sets the frequency weighting
• FAST, SLOW buttons: Sets the response time
• MAX button: Selects MAX, MIN or current measurement; also used to test the
FAST/SLOW characteristics. Press and hold the MAX button for 5 seconds
(MAX will flash on the LCD); press again to exit. For specifics, refer to relevant
sections in this manual.
• MEM button: Press to store a data set in memory
• READ button: Press to read the stored data sets
• Up and Down Arrow buttons: Used to select measurement ranges; also used to
scroll through the stored data sets in the MEM (memory) mode.
5. CAL potentiometer: For calibration. Optional calibrator required.
6. External 9VDC power adaptor
7. DC/AC analog output: Retransmission of sound level measurement for chart recorder
or other datalogger
8. Tripod Mount
9. Battery compartment
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With Memory
Model 407738 Version 2.2 September 2005 3
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