Extech 407768 Operating Manual

User's Manual

Digital Sound Level Meter

Model 407768

Introduction

Congratulations on your purchase of the Extech 407768 Sound Level Meter. This Auto
Range Sound Level Meter meets ANSI and IEC Type II accuracy standards. Professional
features include programmable Frequency Weighting and Time Response, Min/Max
Memory, Max Hold, Analog output, and RS-232 PC Interface. Careful use of this meter will
provide years of reliable service.

Specifications

Display 5 Digit LCD with overload, low battery and multifunction

Frequency bandwidth 31.5 Hz to 8 KHz
Microphone 0.5” Electret Condensor Microphone
Output terminals Optically isolated RS-232 port and AC output
Measurement ranges Auto Range: 30 to 130dB

Frequency weighting ‘A’ and ‘C’ (Programmable)
Applicable standards ANSI / IEC Type 2
Resolution 0.1dB
Maximum/Minimum record Highest and lowest readings are stored for later recall
Data Hold Displayed reading is held when HOLD key is pressed
Max Hold Highest reading displayed only
Response time Fast: 125ms / Slow:1s (Programmable)
AC Analog output
Power 9V Battery; Consumption: 6mADC approx.
Operating temperature 32 to 122oF (0 to 50oC)
Operating humidity Less than 80% RH
Dimensions / Weight 10.6 x 2.7 x 1.1" / 0.63 lbs. (268 x 68 x 29mm / 285g)

indication

Manual Ranges: 30 to 80dB, 50 to 100dB, 80 to 130dB

0.5VAC rms full scale (600Ω output impedance)

Meter Description

1. Microphone

2. LCD Display

3. Power, Hold, and Min/Max buttons

4. Max, Weighting, Response Time, & Range buttons

5. AC output jack

6. Calibration potentiometer

7. RS-232 PC interface jack

8. Battery compartment, tilt stand,
and tripod mount on rear

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407768 Version 2.0 06/06

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Sound Level Meter Operation

Meter Power

1. The meter is powered by a 9V battery. The battery compartment is located on the rear
of the meter and the compartment cover is secured by one Phillips screw. When the
battery icon appears on the top left corner of the meter's display, replace the battery.

2. Press the POWER button to turn the meter on. Note that the Meter is equipped with an
Auto Power Off feature that shuts the meter off after 10 minutes. To defeat Auto Power
Off, put the meter in Record mode by pressing the REC MAX/MIN button.

3. Press the POWER button to turn the meter off.

Default Configuration

1. The meter's default configuration is as follows: Auto Range, 'A' Frequency Weighting,
and 'FAST' Response Time

2. The lower portion of the LCD will reflect the meter's configuration, i.e., 'A', 'Fast', 'Auto'.

Measurement Considerations

1. Use a windscreen (not included) to cover the microphone in windy conditions.

2. Calibrate the meter often, especially if the meter has been idle for a long period of time.

3. Do not store/operate the meter in areas of high temperature or humidity.

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 lower left-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 lower left-hand 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 RANGE button to scroll through the following ranges: Auto, 30-80dB, 50-100dB,
and 80-130dB. The display will reflect the range for each button press.

Calibration

The Sound Level meter should be calibrated before each use; an external sound level
meter calibrator is required. Set the meter to the Manual range (50-100dB), FAST
response and ‘A’ weighting before starting.

1. Place the external calibrator over the Sound Level Meter's microphone and turn the
Calibrator on.

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407768 Version 2.0 06/06