Extech Instruments 407740 User manual

User's Guide

Digital Sound Level Meter

Model 407740

Introduction

Congratulations on your purchase of the Extech 407740 Digital Sound Level Meter. This

device measures sound in decibels (dB). Useful features include A/C Weighting,

Fast/Slow Response Time, and Maximum Reading HOLD. Careful use of this meter will

provide years of reliable service.

Model 407740 version 1.6 8/05



Support Hotline (781) 890-7440

Tech support: Ext. 200; Email: [email protected]

Repair/Returns: Ext. 210; Email: repair@extech.com

Website: www.extech.com

Warranty

EXTECH INSTRUMENTS CORPORATION warrants this instrument to be free of defects

in parts and workmanship for one year from date of shipment (a six month limited

warranty applies on sensors and cables). If it should become necessary to return the

instrument for service during or beyond the warranty period, contact the Customer

Service Department at (781) 890-7440 ext. 210 for authorization or visit our website at

www.extech.com (click on ‘Contact Extech’ and go to ‘Service Department’ to request an

RA number). A Return Authorization (RA) number must be issued before any product is

returned to Extech. The sender is responsible for shipping charges, freight, insurance

and proper packaging to prevent damage in transit. This warranty does not apply to

defects resulting from action of the user such as misuse, improper wiring, operation

outside of specification, improper maintenance or repair, or unauthorized modification.

Extech specifically disclaims any implied warranties or merchantability or fitness for a

specific purpose and will not be liable for any direct, indirect, incidental or consequential

damages. Extech's total liability is limited to repair or replacement of the product. The

warranty set forth above is inclusive and no other warranty, whether written or oral, is

expressed or implied.

Specifications

Display 2000 count multi-function LCD

Input Signal Range ‘A’ Weighting: 30 to 130dB

‘C’ Weighting: 30 to 130dB

Response Time Fast: Response = 125ms; Slow: Response = 1s

Resolution 0.1 dB

Standards Compliance ANSI and IEC Type 2

Accuracy (at 23o± 5 o C) ±1.5dB at 1KHz (94dB)

Frequency 31.5 to 8,000Hz

Microphone Electric condenser microphone, 0.5" (12.7mm)

Range Selector Switch 30 to 80dB, 50 to 100dB, 80 to 130dB

External Calibrator Use Extech model 407744 or 407766

Analog Output Signal AC: 0.5Vrms (full scale of selected range)

DC: 0.3 to 1.3VDC, 10mV/dB

Analog output impedance 600 ohms

Analog Output Terminal 3.5mm phone jack

Operating Temperature 32 °F to 122 °F (0 °C to 50 °C)

Operating Humidity Max. 90% RH (0° to 35°C)

Power Supply 9V battery

Dimensions / Weight 10 x 2.8 x 1.1” (255 x 70 x 28mm) / 10 oz. (280 g)

Model 407740 version 1.6 8/05

Meter Description

1. Microphone

2. LCD Display

3. Calibration potentiometer

Note: Adjust pot only while using an acoustic Calibrator

4. Selector Switches

5. Maximum Hold reset button

6. Analog output jack

The battery compartment and tripod mount are located

on the rear of the instrument

Operation

Powering the Meter and Configuring the Analog Output

Slide the POWER switch to the ON (DC) or ON (AC) position. The (AC) or (DC) determines

the type of signal present at the analog output jack.

Basic Measurements

Point the microphone toward the source of the sound to be measured. The meter can be

held in hand or mounted on a tripod (tripod mount on rear of instrument). The meter will

now display the sound level in dB.

Selecting ‘A’ or ‘C’ Weighting

Use the Weighting selector 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 (the readout does

not boost or dampen the measurement across the frequency spectrum). ‘C’ weighting is

suitable for the operational maintenance and analysis of machinery, motors, pumps,

engines, etc.

Selecting FAST or SLOW response

Use the RESPONSE switch to select Fast or Slow. The setting is determined by the

application and any directives or standards related to the application. For example, most

hearing conservation or OSHA related testing is done using the SLOW setting (with ‘A’

weighting). To capture quick sound peaks, however, use the FAST setting.

Selecting the Measurement Range

Select the measuring range using the ‘dB’ selector switch. If the high (▲) or low (▼)

indicators appear on the display, select a lower range (for ▲) or higher range (for ▼).

Maximum Hold Function

Select MAX HOLD using the RESPONSE selector switch to capture the maximum dB

level. The meter response will be set to FAST. The display will only display the highest

reading in this mode. To reset the Maximum Hold display, press the black reset button on

the bottom of the meter next to the analog output jack.

Calibration

Frequent calibration using an acoustic calibrator is recommended. Follow the instruction

provided with the calibrator.

Model 407740 version 1.6 8/05

Battery Replacement

The low battery indication (BAT) appears on the LCD when the 9V battery is nearing

depletion. Reliable readings can be obtained for several hours after the first appearance of

the low battery indication. To replace the battery, slide the battery compartment cover off

the rear of the instrument and replace the 9V battery. Secure the cover before use.

Reference Information

Frequency Weighting Characteristics

Frequency (Hz) A Weighting C Weighting Tolerance (IEC 651 Type 2)

31.5 -39.4dB -3dB ±3dB

63 -26.2dB -0.8dB ±2dB

125 -16.1dB -0.2dB ±1.5dB

250 -8.6dB 0dB ±1.5dB

500 -3.2dB 0dB ±1.5dB

1 k 0dB 0dB ±1.5dB

2 k +1.2dB -0.2dB ±2dB

4 k +1dB -0.8dB ±3dB

8 k -1.1dB -3dB ±5dB

Typical A-Weighted Sound Levels

Calibration and Repair Services

Extech offers repair and calibration services for the products we sell. Extech also provides

NIST certification for most products. Call the Customer Service Department for information

on calibration services available for this product. Extech recommends that annual

calibrations be performed to verify meter performance and accuracy.

50HP Siren (100')

130

120

110

100

140

Jet takeoff (200')

Riveting machine

Chain saw

Subway (20') Boiler room

Pneumatic drill (50') Freight train (100')

Vacuum cleaner (10') Speech (1')

Large store Large Office

Small office Residence

Night residential area

Whisper (5'0) Sound studio

Threshold of hearing

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