407764 Datasheet, PDF (4/12 Pages) Extech Instruments Corporation. – Datalogging Sound Level Meter

Measurement Preparation
• Read the following safety information before attempting to operate the meter
• Use the meter only as specified or the meter's built-in protection may be impaired.
Maintenance & Cleaning
• Service not covered in this manual should be performed by qualified personnel
• Periodically wipe the case with a dry cloth. Do not use abrasives or solvents.
Battery Replacement
When the battery voltage drops to a critical level, the symbol appears on the LCD. Replace
batteries as soon as possible after the battery symbol appears. The batteries (4 AA) are located
in the rear battery compartment. Remove the single Philips head screw (center rear) for access
to the batteries.
Measurements
Default Configuration
1. The meter's default configuration is as follows: 40 to 90dB, 'A' Frequency Weighting, and
'FAST' Response Time
2. The LCD will reflect the meter's configuration.
Measurement Considerations
1. Use a windscreen to cover the microphone in windy conditions.
2. Calibrate the meter often, especially if the meter has not been used for a long time.
3. Do not store/operate the meter in high temperature/humidity for long periods of time.
4. Keep the meter and the microphone dry.
5. Avoid severe vibration when using the meter.
6. Remove the battery when the meter will be stored for long periods of time.
Frequency Weighting
Change the Frequency Weighting by pressing the 'A/C' button. The 'A' or 'C' icon will display on
the right-hand area of the LCD.
Note: With ‘A’ weighting selected, the meter responds like the human ear (boosting and cutting
the noise amplitude over the frequency spectrum - see Appendix). ‘A’ weighting is used for
environmental measurements, OSHA regulatory testing, law enforcement, and workplace
design. Select ‘C’ weighting for flat response measurements (no boost or cut). ‘C’ weighting is
suitable for the sound level analysis of machines, engines, etc. Most OSHA related testing is
performed using 'A' Weighting and SLOW Response Time settings.
Response Time
Change the Response Time by pressing the 'FAST/SLOW' button. The 'FAST' or 'SLOW' icon
will display on the upper area of the LCD.
Note: Select FAST to capture noise peaks and noises that occur very quickly. In FAST mode,
the meter responds in 200ms. Select the SLOW Mode (meter responds in 500ms) to monitor a
sound source that has a reasonably consistent noise level or to average quickly changing
levels. Selection of Fast or Slow is determined by the application and any directives or
standards related to that application.
Auto/Manual Range
Press the LEVEL button up arrow to scroll through the following ranges: 30-80dB, 40-90,
50-100dB, 60-110, 70-120, 80-130 and 30-130dB (auto). The display will reflect the range for
each button press.
Notes: Use Auto Range when the noise source is relatively steady. Use one of the Manual
ranges may be required if the dB levels are changing over a wide range.
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Model 407764 Version 2.1 9/07