407738 Datasheet, PDF (6/8 Pages) Extech Instruments Corporation. – Digital Sound Level Meter

Measurement Considerations
1. Wind blowing across the microphone increases the noise 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. Protect the meter from impact. Do not drop it. Transport the
meter in the supplied case.
6. Remove the battery when the meter is to be stored for long periods of time.
Notes on ‘A’ and ‘C’ Frequency Weighting
Use the ‘A’ and ‘C’ buttons to select ‘A’ or ‘C’ frequency weighting. With ‘A’ weighting
selected, the frequency response of the meter is similar to the response of the human ear.
‘A’ weighting is commonly used for environmental or hearing conservation programs such
as OSHA regulatory testing and noise ordinance law enforcement. ‘C’ weighting is a much
flatter response and is suitable for the sound level analysis of machines, engines, etc.
Most noise measurements are performed using 'A' Weighting and SLOW Response.
Notes on ‘FAST’ and ‘SLOW’ Response Time
Use the FAST and SLOW buttons to select a FAST (125 ms) or a SLOW (1 second)
response time. Select FAST to capture noise peaks and noises that occur very quickly.
Select the SLOW response to monitor a sound source that has a consistent noise level or
to average quickly changing levels. Select SLOW response for most applications.
Storing and Recalling Readings
Storing readings
Press the MEM button momentarily to store a reading. The meter will store the current
measurement, the current MAX & MIN values, and the elapsed time. The display icon ‘M’
will appear briefly when the MEM button is pressed along with the storage location (01
through 99). The ‘FULL’ display icon will appear when the meter’s internal memory has
reached capacity (99 readings).
Recalling readings
1. Press the READ button to enter the recall mode (the ‘R’ display icon will appear on the
LCD).
2. Use the arrow keys to scroll through the stored reading list. The memory location
number displays for each stored reading (01 through 99).
3. Use the MAX button to scroll through the MAX, MIN, and Elapsed Time data stored at
the current location.
4. Press the READ button again to exit the recall mode.
Clearing Stored readings
1. Turn the meter OFF.
2. Press and hold the MEM button while turning the meter ON.
3. When the ‘CLr’ (clear) display icon appears, release the MEM button.
4. All of the readings that were stored in memory are now erased.
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Model 407738 Version 2.2 September 2005