Extech Extech 407736-NIST Manual

99 Washington Street
Melrose, MA 02176

Phone [phone]
Toll Free 1-800-517-8431

Digital Sound Level Meter

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• 1.5 dB accuracy meets ANSI and IEC 651
Type II standards

• A/C weighting & Fast/Slow response

• Built-in calibration check

• 0.1dB resolution

INTRODUCTION

Congratulations on your purchase of the Extech Model 407736 Digital Sound Level Meter.
This professional meter, with proper care, will provide years of safe reliable service.

Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176

FAX [phone] - TestEquipmentDepot.com

SPECIFICATIONS

Display 3-1/2 digit (2000 count) LCD

Display update rate 0.5 seconds

Microphone 0.5” Electret condensor

Measurement Bandwidth 31.5Hz to 8KHz

Dynamic range 55dB

Measurement Range 35 to 130dB (Low: 35 to 90; High: 75 to 130dB)

Frequency weighting ‘A’ and ‘C’ (selectable)

Applicable standards IEC-651 & ANSI S1.4 Type 2

Accuracy / Resolution ± 1.5dB / 0.1dB

Maximum Hold decay time <1dB / 3min

Response time Fast: 125 milliseconds / Slow: 1 second

Built-in calibration check 1KHz internal sine wave @ 94dB

AC Analog output

DC Analog output

0.65VAC rms (full scale); 600Ω output impedance

10mVDC / dB; 100Ω output impedance (approx).

Power 9V Battery

Battery life 50 hours (typical); Low battery indicator alerts user

Operating temperature 32 to 104oF (0 to 40oC)

Operating humidity 10 to 90% RH

Dimensions/weight 9.45 x 2.68 x 1” (240 x 68 x 25mm) / 6.75oz (210g)

METER DESCRIPTION

1. Microphone

2. LCD display

3. POWER OFF & RANGE select switch

4. RESPONSE & HOLD select switch

5. A/C weighting and Calibration switch

6. Calibration adjust screw for 94dB

7. Reset key (resets max hold reading)

8. AC/DC analog output 3.5mm phone jack

9. Battery compartment and Tripod mount are located
on back of meter

MEASUREMENT CONSIDERATIONS

1. Wind blowing across the microphone adds extraneous noise to the measurement.
Use the supplied windscreen to cover the microphone when applicable.

2. Calibrate the instrument before each use if possible. Especially if the meter has not
been used for a long period of time.

3. Do not store or operate the instrument in areas of high temperature or humidity.

4. Keep meter and microphone dry.

5. Avoid severe vibration when using the meter.

6. Remove the battery when the meter is to be stored for long periods of time.

407736 Ver. 1.4 January 2002

2

METER OPERATION

Quick Start

1. Power the meter by moving the RANGE switch to the LO or HI position. The meter will
begin displaying sound levels. If the LCD does not display, check that the battery is
good.

2. Place the meter on a tripod or hold the meter in hand facing the microphone toward the
source of the sound to be measured. Note that the tripod mount is on the back of meter.

3. View the measurement on the meter’s LCD. An indication of ‘OVER’ means that the
measurement is out of range. Select another measurement range in the event of an
over-range condition.

‘A’ and ‘C’ Frequency Weighting

Use the FUNCT (function) switch to select ‘A’ or ‘C’ frequency weighting. Use ‘A’ weighting
to have the meter simulate the response of the human ear (the human ear boosts and cuts
sound levels at specific points over the frequency spectrum). ‘A’ weighting is used for
environmental measurements, OSHA regulatory testing, law enforcement, and workplace
design. Select ‘C’ weighting for flat response measurements (no boosting or dampening
across the frequency spectrum). ‘C’ weighting is suitable for the operational maintenance
and analysis of machinery, motors, pumps, engines, etc.

FAST/SLOW Response Time

Use the RESPONSE switch to select FAST (125 ms) or SLOW (1 second) response time.
The application at hand (and any directives or standards) will dictate which response to
select. For example, most hearing conservation or OSHA related testing is done using
SLOW mode and ‘A’ weighting.

MAX HOLD

In this mode, the meter only updates the LCD when a higher reading than the one
presently on the display is detected. Select MAX HOLD using the RESPONSE switch. The
LCD shows ‘MAX HOLD’ in this mode. Press RESET to reset the MAX HOLD reading.

Analog Outputs

The meter includes an AC and a DC analog output for use with chart recorders,
dataloggers, etc. The AC output is 0.65V rms full scale and the DC output is 10mV per dB.
The 3.5mm output jack is located on the right side of the instrument. Use a stereo mini­plug as shown in the diagram below to connect the meter to a datalogger or other recorder.

Stereo plug

Tip: AC Output
Ring: DC Output
Sleeve: Ground

BATTERY REPLACEMENT

When the low battery message appears on the LCD replace the 9V battery as soon as
possible. The battery compartment cover resides at the bottom, rear of the meter. Slide
the battery compartment cover off, change the battery, and replace the compartment
cover.

CALIBRATION CHECK

This meter provides a built-in calibration adjustment. The calibration adjustment
potentiometer is located on the front panel beneath the FUNCT switch. Put the FUNCT
switch to the CAL 94dB position and adjust the potentiometer for a display of exactly
94dB. For calibration with an external sound level calibrator, refer to the instructions
accompanying the calibrator.

407736 Ver. 1.4 January 2002

3

TYPICAL ‘A’ WEIGHTED SOUND PRESSURE LEVELS

dBA

50HP Siren (100')

Jet takeoff (200')

Riveting machine

Subway (20')

Pneumat ic d r ill (50' )

Vacuum cleaner (10')

Large s t ore

Small off ic e

Night residential area

Whisper (5'0)

Threshold of hearing

© 2002 Extech Instruments Corp. All rights reservedincluding the right of reproduction in whol e or in part in any form.

140

130

120

110

100

Chain saw

90

Boiler room

80

Freight train (100' )

70

Speech (1')

60

Large Office

50

Residence

40

30

Sound studio

20

10

0

Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176

FAX [phone] - TestEquipmentDepot.com