Extech 407750, 407750-NIST Instruction Manual

Instruction Manual

MODEL 407750

Digital Sound Level Meter

q Auto/Manual Ranging

q A/C weighting & Fast/Slow response

q Background noise absorption

q RS-232 PC Interface

q The frequency spectral curves of this high resolution

(0.1dB) meter meet ANSI and IEC-651 Type II standards

1. INTRODUCTION

Congratulations on your purchase of the Extech Model 407750 Digital Sound Level Meter.
This professional meter wilth proper care will provide years of safe reliable service.

1 407750 Ver. 1.03 6/99

2. SPECIFICATIONS

Display Backlit Super Large 3-1/2 digit (1999 count) LCD

with 0.8” digits plus analog bargraph and
multifunction displays

Display update rate Main LCD: 0.5 seconds; Bargraph: 50mS
Analog Bargraph 1dB steps with 50dB display range
Microphone Electret condensor (6mm diameter)
Measurement

31.5Hz to 8KHz

Bandwidth
Measurement Range A weighting: 30 to 130dB; C weighting: 35 to 130dB

6 ranges in 10 dB steps: 30 to 80dB, 40 to 90dB, 50
to 100dB, 60 to 110dB, 70 to 120dB, 80 to 130dB

Accuracy / Resolution ± 1.5dB / 0.1dB
Time response

Fast/Slow
selections
Analog output 0.707Vac rms at full scale; 10mVdc/dB
Power 9V Battery (006P or 6F22)
Dimensions/weight 80x256x38mm / 240g

3. METER DESCRIPTION

1. LCD Display

2. Microphone

3. ON/OFF key

4. REC (Record) key

5. MAXHLD (Max Hold) key

6. C/A Weighting Select key

7. BA (Background Absorber) key

8. F/S Fast / Slow Response select key

9. DOWN

10. Backlit (LCD backlighting) key

11. UPPER

12. AC adaptor jack

13. Calibration screw adjust

14. AC analog output jack

15. DC analog output jack

16. RS-232 output jack

17. Battery Compartment (not pictured)

18. Threaded Tripod mount access (not pictured)

4. METER OPERATION

4.1 Quick Start

1. Power the meter by pressing the ON/OFF key. 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 display after pressing the ON/KEY check the 9V battery (see section 5).

2. Place the meter on a tripod via the tripod mount on the rear of the meter or hold
the meter in hand to take noise measurements.

3. Point the microphone toward the source of the sound level to be measured and
view the reading on the meter’s LCD.

4.2 ‘A’ and ‘C’ Weighting. Select ‘A’ or ‘C’ Weighting via the C/A key. The LCD will reflect

which weighting mode is currently selected. 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 therefore it is not ‘flat’
responding). ‘A’ weighting is used for environmental measurements, OSHA regulatory
testing, law enforcement, and workplace design. Select ‘C’ weighting for flat response

2 407750 Ver. 1.03 6/99