User's Guide
Digital Sound Level Meter
Model 407738
With Memory
Introduction
Congratulations on your purchase of the Extech 407738 Digital Sound Level Meter.
The 407738 measures and displays sound pressure levels in dB (decibels) from 26 to
130dB in six measurement ranges. The microphone can be removed and remotely
stationed for convenience. In addition to the LCD numerical displays, a bargraph is
included for quick and easy viewing of sound level changes. Features include selectable
Frequency Weighting (‘A’ and ‘C’), selectable Response Time (Fast and Slow), Max
Hold, and a 99 reading storage utility.
Careful use of this meter will provide years of reliable service.
Specifications
Applicable Standards
Measurement Functions
Primary Functions
IEC61672-1: 2002 Class 2; IEC60651: 1979 Type 2; ANSI S1.4:1983 Type 2
Sound Pressure Level
Maximum Sound Level
Minimum Sound Level
26 to 130dB (32 to 130dB for ‘C’ weighted measurements)
130dB
± 1.5dB (under reference conditions)
‘A’ weighting: 26dB
‘C’ weighting: 32dB
94dB at 1kHz (sinusoidal)
26 to 80, 30 to 90, 40 to 100, 50 to 110, 60 to 120, 70 to 130
31.5 to 8000 Hz
‘A’ and ‘C’
Fast (125ms) and Slow (1 second) Response
Requires external calibrator (not included)
Bargraph display: 125ms; Numerical indication: 1 second
99 data sets (max.) for sound level (L), maximum sound level (Lmax), and
minimum sound level (Lmin) can be stored with elapsed timer.
0.5” electret condensor
4-digit indication of sound level with 0.1dB resolution
Bargraph indication of sound level with 1dB resolution
Elapsed time; 100 hours maximum
Store and recall readings (99 data sets max.)
Over-range ‘OV’; Under-range: ‘Un’
AC: 0.707Vrms full scale; Output impedance: 5KΩ
DC: 10mV/1dB; Output impedance: 5KΩ
9V Battery; Battery life approx. 50 hours
14 to 122
o
F (-10 to 50
o
C); 90% relative humidity max.
14 to 132
o
F (-10 to 60
o
C); 90% relative humidity max.
10.4 x 2.7 x 1.1” (264 x 68 x 27mm)
9.2 oz. (260g)
Total range
Maximum level
Accuracy
Noise floor
Calibration signal
Range selections
Frequency range
Frequency weighting
Time weighting
Calibration
Display update rate
Data memory
Microphone
Display
Display features
Warning indicators
Analog Outputs
Power requirements
Operating conditions
Storage conditions
Dimensions
Weight
Support line (781) 890-7440
Technical support: Extension 200; E-mail: support@extech.com
Repair & Returns: Extension 210; E-mail: repair@extech.com
Product specifications subject to change without notice
For the latest version of this User’s Guide, Software updates, and other
up-to-the-minute product information, visit our website: www.extech.com
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Model 407738 Version 2.2 September 2005
Meter Description
1. Microphone: Electret condenser
2. Microphone collar: unscrew to remove microphone
3. LCD Display
4. Push-buttons:
•
•
•
•
Power button
A,C buttons: Sets the frequency weighting
FAST, SLOW buttons: Sets the response time
MAX button: Selects MAX, MIN or current measurement; also used to test the
FAST/SLOW characteristics. Press and hold the MAX button for 5 seconds
(MAX will flash on the LCD); press again to exit. For specifics, refer to relevant
sections in this manual.
MEM button: Press to store a data set in memory
READ button: Press to read the stored data sets
Up and Down Arrow buttons: Used to select measurement ranges; also used to
scroll through the stored data sets in the MEM (memory) mode.
•
•
•
5. CAL potentiometer: For calibration. Optional calibrator required.
6. External 9VDC power adaptor
7. DC/AC analog output: Retransmission of sound level measurement for chart recorder
or other datalogger
8. Tripod Mount
9. Battery compartment
1
2
3
4
5
6
7
With Memory
8
9
3
Model 407738 Version 2.2 September 2005
Display Description
3 4
1
2
19
8
5 6 7
00
Un
Un
18.8.8
FAST SLOW
L
0
180
Ov
Ov
min
max
18
17
16
15
1dB
88:88:88
11
FULL
00
MR
9 10
1.
2.
3.
4.
5.
6.
7.
8.
9.
Sound Level Range
Bargraph indication
12 13 14
Under-range indicator for current reading
Under-range indicator for reading in memory
Frequency weighting
Over-range indicator for reading in memory
Over-range indicator for current reading
Battery status indicator
FAST response time setting
10. SLOW response time setting
11. Elapsed time indicator (100 hours max.)
12. Memory FULL indicator
13. Memory indicator
14. READ memory indicator
15. Address for stored reading
16. Sound level unit of measure (decibel)
17. Maximum sound level reading
18. Minimum sound level reading
19. Sound pressure level
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Model 407738 Version 2.2 September 2005
Power Supply
The meter can be powered by one 9V battery or by the specified optional AC power
adaptor. Before inserting or replacing the battery and before connecting the AC adaptor,
be sure to turn off the meter.
Battery Installation
Remove the battery compartment cover (lower back of the meter) and install or replace the
9V battery.
Fully charged
Battery Capacity Indicator
The battery status indicator on the meter’s display (see diagram)
informs the user of the battery’s condition. The number of segments in
the display icon decreases as the battery weakens. When all segments
switch off and the icon flashes, the meter is about to lose power.
AC Voltage Adaptor
Insert the AC adaptor into the DC 9V jack on the side of the meter.
Connect the other end of the adaptor to an AC source. With a battery
installed and the AC adaptor in use, the AC adaptor has priority.
Partially charged
Replace battery
Measurements
1. Turn the meter ON by pressing the
button. The default settings are: ‘A’ frequency
response; ‘FAST’ response time; and 70 to 130dB range
2. Select the frequency weighting ‘A’ or ‘C” as desired using the ‘A’ or the ‘C’ buttons.
Typical sound level measurements use ‘A’ weighting.
3. Press the ‘FAST’ or ‘SLOW’ button to select the desired response time. Normally the
‘SLOW’ setting is used.
4. Use the up and down buttons to select the appropriate range. The range is shown at the
top left corner (low end of range) and top right corner (high end of range) of the LCD.
Use a range that puts the sound level reading in the center of the bargraph. If the OV
(over-range) or UN (under-range) icons appear with dashes on the main display area,
select a new range. Refer to the Specifications page for the list of available ranges.
5. The numeric and bargraph displays indicate the sound level measurement. The
numerical reading updates every second while the bargraph updates every 125ms.
MAX / MIN Operation
The Model 407738 stores the highest (MAX) and lowest (MIN) readings in its memory. The
stored MAX and MIN values are continually updated as new MAX and MIN values are
encountered. The user can recall these stored readings using the MAX button as
described in the steps below. Before starting, select an appropriate range as described
previously, otherwise the stored MIN/MAX readings may indicate all dashes (out of range).
1. Press the MAX button and the MAX icon will appear on the LCD. The reading shown is
the highest reading encountered since the meter was last reset. Note that the elapsed
timer display shows the time at which the MAX reading was recorded.
2. Press the MAX button again. The MIN icon will appear on the LCD and the reading
shown represents the lowest reading encountered since the meter’s memory was last
reset. The elapsed timer display shows the time at which the MIN reading was recorded.
3. Press the MAX button again to exit the MAX / MIN display mode (the MAX and MIN
display icons switch off when this mode is exited).
4. To clear the MAX / MIN memory, simply press the up or down arrow to change range.
Note that the elapsed timer starts when the meter is switched ON and continues running
until the meter is shut off or until 100 hours is reached.
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Model 407738 Version 2.2 September 2005
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