407740 Datasheet, PDF (3/4 Pages) Extech Instruments Corporation. – Digital Sound Level Meter

Meter Description
1. Microphone
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2. LCD Display
3. Calibration potentiometer
Note: Adjust pot only while using an acoustic Calibrator
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4. Selector Switches
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5. Maximum Hold reset button
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6. Analog output jack
The battery compartment and tripod mount are located
on the rear of the instrument
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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.
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Model 407740 version 1.6 8/05