407750 Datasheet, PDF (4/8 Pages) Extech Instruments Corporation. – Digital Sound Level Meter

Operation
Quick Start
1. Power the meter by pressing the ON/OFF key.
2. The meter’s LCD will count down to zero (99.9, 88.8, 77.7, etc.) and then begin
measuring sound levels. If the LCD does not switch on after pressing the ON/KEY
check the 9V battery.
3. Point the microphone toward the source of the sound level to be measured and view
the reading on the meter’s LCD.
‘A’ and ‘C’ Frequency Weighting
Select ‘A’ or ‘C’ weighting via the C/A key. The LCD will reflect the currently selected
frequency weighting. Use ‘A’ weighting to have the meter respond as the human ear would
with regard to frequency response (the human ear boosts and cuts amplitude over the
frequency spectrum). ‘A’ weighting is used for environmental measurements, OSHA
regulatory testing, law enforcement, and workplace design. Select ‘C’ weighting for flat
responding measurements (less amplitude boost or cut across the frequency spectrum).
‘C’ weighting is used in applications where hearing conservation is not an issue; for
example, in the diagnosis of malfunctions in electrical, electronic and mechanical devices.
FAST/SLOW Response Time
Select either FAST (125ms response) or SLOW (1 second response) measurements by
pressing the F/S key. The LCD will reflect the currently selected mode. Selection of ‘Fast’
or ‘Slow’ is determined by the application and any directives or standards related to that
application. For example, most hearing conservation or OSHA related testing is done using
SLOW and A weighting.
MAX HOLD
The meter is capable of taking continuous measurements and only updating the LCD when
a higher reading (than the one presently on the display) is detected. The bargraph display
continues to change while the main LCD waits for a higher reading. Press the MAXHLD
key to activate the MAX HOLD mode. The LCD will reflect the MAX HOLD function. Press
the MAXHLD key again to return to normal operation.
Record (REC) Function
To Record the Maximum and Minimum sound level measurements over a programmable
period of time, press the REC key. The REC indicator will appear on the LCD. Once the
REC key is pressed, the meter begins tracking the highest (MAX) and lowest (MIN)
readings. Press the REC again and the MIN indicator will appear on the LCD along with
the lowest sound level reading since the REC key was pressed. Press the REC again and
the MAX indicator will appear along with the highest reading the meter has encountered
since the REC key was first pressed. Press and hold the REC until the REC indicator
extinguishes to exit the RECORD mode.
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Model 407750 Version 2.1 February 2004