Extech Instruments 407735 User manual

User's Guide
Digital Sound Level Meter
Model 407735
Introduction
Congratulations on your purchase of the Extech Model 407735 Digital Sound Level Meter.
This professional meter, with proper care, will provide years of safe reliable service.

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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 65dB
Measurement Range 35 to 130dB (Low: 35 to 90; High: 65 to 130dB)
Frequency weighting ‘A’ and ‘C’ (selectable)
Accuracy / Resolution ± 2.0dB @1kHz / 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 0.65VAC rms (full scale); 600Ωoutput impedance
DC Analog output 10mVDC / dB; 100Ωoutput 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.

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Operation
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 mini-
plug as shown in the diagram below to connect the meter to a datalogger or other recorder.
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.
Tip: AC Output
Ring: DC Output
Sleeve: Ground
Stereo plug

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Support Hotline [phone]
Tech support: Ext. 200; Email: [email protected]
Repair/Returns: Ext. 210; Email: [e-mail]
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 [phone] 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.
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.
Typical “A” Weighted Sound Pressure Levels
Copyright ©2003 Extech Instruments Corporation
All rights reserved including the right of reproduction in whole or in part in any form.
50HP Siren (100')
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90
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40
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10
140
0
Jet takeoff (200')
dBA
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