Extech Instruments 407790 User manual

[ 1 / 3 OCT ] 01 / 07 / 27 14:26:39
100 WA
L
Hz 125
30
50
31.5 500
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90
dB
FAST 75.2 dB
8k2k LW
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User Manual
Real Time Octave Band Analyzer
Model 407790
Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176
FAX [phone] - TestEquipmentDepot.com
99 Washington Street
Melrose, MA 02176
Phone [phone]
Toll Free 1-800-517-8431
Visit us at www.TestEquipmentDepot.com
Back to the Extech 407790 Product Page

Model 407790 Ver. 1.1 7/02L
2
Warranty
EXTECH INSTRUMENTS CORPORATION warrants this instrument to be free of defects in parts and
workmanship for one year from date of shipment (a six month limited warranty applies on sensors and
cables). If it should become necessary to return the instrument for service during or beyond the warranty
period, contact the Customer Service Department at [phone] ext. 210 for authorization or visit our
website at www.extech.com (click on ‘Contact Extech’ and go to ‘Service Department’ to request an RA
number). A Return Authorization (RA) number must be issuedbefore any product is returned to Extech. The
sender is responsible for shipping charges, freight, insurance and proper packaging to prevent damage in
transit. This warranty does not apply to defects resulting from action of the user such as misuse, improper
wiring, operation outside of specification, improper maintenance or repair, or unauthorized modification.
Extech specifically disclaims any implied warranties or merchantability or fitness for a specific purpose and
will not be liable for any direct, indirect, incidental or consequential damages. Extech's total liability is limited
to repair or replacement of the product. The warranty set forth above is inclusive and no other warranty,
whether written or oral, is expressed or implied.
Introduction
Congratulations on your purchase of the Extech 407790 Real Time Octave Band
Analyzer. This auto ranging Type 2 integrating sound level meter features 1/1 and 1/3
Octave Band real-time noise analysis. The 407790 offers five measurement parameters:
SPL (Sound Pressure Level), Leq (Equivalent Continuous Sound Pressure Level), LE
(Sound Exposure Level), Lmax (Maximum Sound Pressure Level), and Lmin (Minimum
Sound Pressure Level). The built-in memory stores 12,280 data records in sound level
mode and 1024 records in Octave mode. The stored data can be easily transferred to a
PC with the supplied software and RS-232 cable. This meter permits choice of ‘A’, ‘C’, or
‘Flat’ weighting and ‘Slow’ / ‘Fast’ response times. AC and DC analog output signals are
available for chart recorders and other external recording devices. Careful use of this
device will provide years of reliable service.
Specifications
Applicable Standards: IEC 60651 type2, 60804 type 2, ANSI S1.4 type2, IEC 1260 (1995)
Display: Backlit LCD (160×160 dot matrix)
Sound level meter mode:
Numeric display: 4 digits; Update rate: 0.5 seconds; Resolution: 0.1 dB
Bar graph display: 100dB range; Update rate: 0.125S; Resolution: 1dB
Frequency analysis mode:
Numeric display: 4 digits; Update rate 0.5 seconds; Resolution: 0.1dB
Bar graph display: 70dB range; Update rate: 0.125S; Resolution: 1 dB
Accuracy:
±1.5dB (ref 94dB @1kHz)
Measurement Frequency range: 25Hz to 10 kHz
Dynamic range: 100dB (Sound level meter mode); 70dB (Frequency analysis mode)
Measurement range: 30dB to 130dB
Sound Pressure Level range: SLM mode: 100dB (30 to 130dB); Frequency analysis mode:
70dB (20 to 90dB, 30 to 100dB, 40 to 110dB, 50
to 120dB, 60 to 130dB
Frequency weighting: ‘A’, ‘C’, ‘P’ (Flat)
Time weighting (Response Time): Fast and Slow
Microphone: 1/2 inch electret condenser type

Model 407790 Ver. 1.1 7/02L
3
Display warning indicators:
OVER indicator (Input signal exceeds the upper limit)
UNDER indicator (Input signal under the lower limit)
Memory capacity: See Table below (Manual/Auto storage blocks are separate)
Storage type
Mode Manual Auto
Sound level meter 1024 data sets 10000 data sets
1/1-octave analysis 1024 data sets 6140 data sets
1/3-octave analysis 1024 data sets 3070 data sets
AC output: 2 Vrms at FS (full scale); Output impedance approx. 600Ω
DC output: 10mV/dB; Output impedance approx. 100Ω
Power: Four (4) C size 1.5V alkaline batteries
External DC power supply: 6 Vdc, 1A
Battery life: Approx. 2hours
Operating Temperature/Humidity: 32 to 104oF (0 to 40℃); 10 to 90%RH
Storage Temperature/Humidity: 14 to 140oF (-10 to 60℃); 10 to 90%RH
Environment conditions: Altitude up to 2000 meters
Safety symbol
Complies with EMC
Dimensions & Weight: 13.6 (H) x 4.0 (W) x 2.4 (D)” (34.5 × 10 × 6cm); Approx.33.5 oz.
(950g) including batteries
Accessories: Four (4) C 1.5V batteries, hard-shell carrying case, CD-ROM WindowsTM
software, RS-232 cable, 9 pin to 25 pin adapter, adjustment screw driver, Windscreen,
3.5mm plug, and AC adaptor
Optional accessories: Microphone extension cable (5m or 10m), Sound level calibrator

Model 407790 Ver. 1.1 7/02L
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Meter Description
Refer to the diagram below for the following descriptions.
1. Windscreen
2. Microphone
3. Display
4. Operation keys
5. Power switch
6. Calibration adjust knob
7. 6VDC adapter jack
8. DC analog output jack
9. AC analog output jack
10. LCD contrast adjust knob
11. LCD backlight on/off switch
12. Hand strap
13. RS-232 interface connector
14. Battery compartment
15. Tripod mounting screw
FAST L
2k
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20
40
31.5Hz 500125
60
80
dB
100 A W
W8k L
65.2 dB
IEC 1260 CLASS2
OFFON
POWERCAL
IEC LR14 1.5V X 4
ACCURACY : ¡ Ó1.5dB
OFFON
DCAC
CONTRAST
OUTPUT
DC6VLIGHT
SOUND ANALYZER
IEC 651 IEC 804 TYPE 2
1/1 & 1/3 OCTAVE BAND
Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176
FAX [phone] - TestEquipmentDepot.com

Model 407790 Ver. 1.1 7/02L
5
Operation Buttons
Refer to the diagram on the next page for the following button descriptions.
MODE button
Press to display the following: Sound pressure level (L), equivalent continuous sound
pressure level (Leq), Sound exposure level (LE), maximum sound pressure level
(Lmax), and minimum sound pressure level (Lmin).
FREQ WGHT button
Selects the frequency weighting. “A” weighting (A), “C” weighting (C), and flat
frequency response (P).
TIME CONST button
Selects the response time “FAST” and “SLOW”.
LEVEL
Press to select the sound pressure level ranges in 1/1 and 1/3 octave band frequency
analysis mode. (20~90dB, 30~100dB, 40~110dB, 50~120dB and 60~130dB)
SLM/ 1/1/ 1/3 button
Press to select the operation mode: Sound level meter (SLM), 1/1-octave frequency
analysis (1/1), and 1/3-octave frequency analysis (1/3).
MEAS TIME button
Sets the Leq, LE, Lmax and Lmin measurement time :
24h1s3s10s30s1m5m8m10m15m
30m1h8h
 2nd + MEAS TIME : Enter to setting the date and time mode.
MEMORY button
 Enter to memory mode.
 2nd + MEMORY : Enter to data record interval time setting : 0 (no record)
1s 3s10s 30s1m5m8m10m15m30m1h62.5ms
ENTER button
Stores the new date and time (also starts the real-time calendar clock)
Cursorbutton
Press to move the octave frequency band marker during frequency analysis.
2nd+ Cursor: Use in recall mode to select the memory address in which to
store the measurement data.
START/STOP button
Press to start or stop the Leq, LE, Lmax and Lmin sound pressure level
measurement.
PAUSE/CONT button
Press to temporarily pause ( display) or resume (display )
2nd button: Press to change the buttons to their secondary functions.

Model 407790 Ver. 1.1 7/02L
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STORE button
In manual dataloggin mode, press to store the measurement data.
RECALL button
In manual memory mode, press to recall the stored memory data.
STORE + RECALL key (Erase memory data)
Turn off the meter, press and hold the STORE and RECALL buttons and then turn
on the meter. Release buttons when the LCD displays “All memory erased”.

Model 407790 Ver. 1.1 7/02L
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Measurement Screens
1. Sound pressure level measurement screen
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A
L
30 80
FAST dB
130
2. 1/1-octave analysis screen
The staircase shape on the display represents the 1/1-octave analysis result. From left,
the bars correspond to 31.5, 63, 125, 250, 500, 1k, 2k, 4k, 8kHz. To read the levels at
these frequencies, use the Cursorkey to move the cursor to the desired point.
The frequency and level are then shown on the upper of the screen.
68.4 dB
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50
31.5 125Hz
30 8k2k500
AL
100
dB
70
90
FAST 2k Hz
L W
40
60
80
3. 1/3-octave analysis screen
The staircase shape on the display represents the 1/3-octave analysis result. From left,
the bars correspond to 25, 31.5, 40, 50, 63, 80, 100, 125, 160, 200, 250, 315, 400, 500,
630, 800, 1k, 1.25k, 1.6k, 2k, 2.5k, 3.15k, 4k, 5k, 6.3k, 8k, 10kHz. To read the levels at
these frequencies, use the Cursorkey to move the cursor to the desired point.
The frequency and level are then shown on the upper of the screen.

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31.5Hz30
50
70
2k500125 8k L W
A
FAST
90
dB LW 75.2 dB
100
60
80
40
Calibration
Use a standard acoustic calibrator such as the Extech 407744 or
407766. Acoustic calibration if often performed on a daily basis to
compensate for any possible changes in microphone sensitivity.
1. Configure the following switch settings.
Display: SLM (LA)
Time weighting: FAST
2. Insert the microphone carefully into the insertion hole of the
calibrator.
3. Turn on the calibrator and adjust its CAL potentiometer so
that the display matches the calibrator output.
4. Note that the 407790 is fully calibrated before shipment.
5. Recommended full recalibration cycle: 1 year.
Measurement Preparation
1. Battery loading: Remove the rear battery cover and insert four 1.5V ‘C’ size batteries.
Take care to observe battery polarity.
2. Battery replacement: When the battery voltage drops below operating voltage,
3. LBATT flashes on the display.
4. AC adaptor connection: Insert the adaptor in the DC 6V jack on the side panel.
Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176
FAX [phone] - TestEquipmentDepot.com

Model 407790 Ver. 1.1 7/02L
9
Setting the Calendar Clock
Date and time information is stored with each record saved. Set the date and time as follows:
1. Press the 2nd button once and then press the MEAS TIME button to enter the date and
time mode. The display screen in the second function location will flicker.
2. Press the LEVELbutton to increment/decrement the values.
3. Use the Cursorbutton to scroll through year/month/day/hour/minute/second
setting locations (location will flash when it is ready to be programmed).
4. Press the LEVELbutton to set the value.
5. When the settings are correct, press the ENTER button to exit this mode. The calendar
clock will start running.
Note: When no changes are made to the date and time or the ENTER button is not
pressed within one minute, the date and time settings will not change and the unit
returns to normal operating mode automatically.
Sound Pressure Level
Technical notes
1. The decibel (dB)
The range over which the human ear responds to sound pressure (noise) is extremely
large; in Pascals (Pa) it is 20µPa (the threshold of hearing) to 100 Pa (the threshold of
pain). The measurement of sound pressure has been made more convenient by the
use of the decibel, which is logarithmic. However, decibels are non-linear and
therefore cannot be added together. A simple rule is that doubling the amplitude of the
noise under test causes the level to rise by 3dB.
2. SLM-sound level meter: Instantaneous sound pressure level (SPL) is used for spot
checks to establish instantaneous noise levels. SPL is defined by the logarithmic
equation:
SPL (in dB): 20 log10
0P
P
Where P = rms measured sound pressure level
P0= rms reference sound pressure level (20µPa)
3. Leq-level equivalent (continuous): Leq is used to assess the rms average noise level
over a preset period of time, often the starting point of a noise assessment. To take a
Leq measurement the period of time over which it is to be made must be selected.
The longer the period of measurement time, the more accurate the Leq reading will be,
a typical period is 8 hours (the length of a working day).
4. LE– Sound exposure level
LEmeasurements are almost identical to Leq measurements but normalised or
compressed to 1 second. This allows the total sound energy of an event, such as train
passing a platform, to be evaluated. Another event, such as the next train, which lasts
for a different amount of time, can be measured in the same way. The two readings
can be compared to assess how much total noise the passengers standing at the
platform were exposed to by each train. To make an LEmeasurement either a preset
time period must be selected on the instrument, or the PAUST/CONT key must be
used to stop and start the measurement of a specific event.

Model 407790 Ver. 1.1 7/02L
10
Instantaneous sound pressure level measurement (LA, LC, LP)
To perform a measurement, carry out the following steps.
1. Set the power switch to ON and wait until the measurement screen appears.
ID No: 00001358 Ver: 0.10
SOUND LEVEL METER
1/1 & 1/3 Octave Band
Real-Time Analyzer
Self-Testing... [ SLM ] 01 / 07 / 27 14:26:39
A
L
30 80
FAST dB
130
2. Press the SLM/ 1/1/ 1/3 button to select the desired SLM, 1/1 or 1/3 octave band
sound pressure level measurement screen.
70
500
[ 1 / 1 OCT ] 01 / 07 / 27 14:26:39
125Hz 31.5
30
50
8k L W2k
A
FAST L
90
dB 75.2 dBW
40
60
100
80
[ 1 / 3 OCT ] 01 / 07/ 27 14:26:39
31.5Hz30
50
70
2k500125 8k L W
A
FAST
90
dB LW 75.2 dB
100
60
80
40
3. Use the FREQ WGHT button to select the desired LA, LCor LPfrequency weighting
setting.
4. Use the TIME CONST button to select the desired FAST or SLOW time constant
setting. Normally, the “FAST” setting should be used.
5. Use the
LEVELbutton to select the range. Choose a setting in which the “OVER”
and “UNDER” indications do not appear. In SLM mode, the dynamic range is
30~130dB so the LEVELbutton is not used.

Model 407790 Ver. 1.1 7/02L
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[ 1 / 1 OCT ] 01 / 07 / 27 14:26:39
500
70
125Hz 31.5
60
40
30
50
A
FAST L
100
80
90
dB
WL8k2k
75.2 dBW
Leq and LEmeasurement
To perform a measurement, carry out the following steps.
1. Set the power switch to ON and wait until the measurement screen appears.
2. Press the MEAS TIME button to set the preset measurement time (known as the integral
time) after which measurement automatically stops.
There are 13 preset time settings available:
•1s •10min
•3s •15min
•10s •30min
•30s •1h
•1min •8h
•5min •24h
•8min
Note: The setting will wrap around from 24h to 1s.

L
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FAST A W 75.2 dB
100
Hz 31.5 125 500 2k WL8k
dB
90
70
50
30
60
40
80
3. Use the LM/ 1/1/ 1/3 button to select the desired SLM, 1/1 or 1/3 octave band sound
pressure level measurement screen.
4. Use the FREQ WGHT button to select the desired LA, LC or LPfrequency weighting
setting.
5. Use the TIME CONST button to select the desired FAST or SLOW time constant setting.
Normally, the “FAST” setting should be used.
6. Use the
LEVELbutton to select the level range. Choose a setting in which the
“OVER” and “UNDER” indications do not appear. In SLM mode, the dynamic range is
30~130dB, so the LEVELkey is not activated.
7. Press the START/STOP button. The “” mark appears on the display and the
equivalent continuous sound pressure level measurement begins.
8. The following status displays are used in the mode “measuring”, “ pause ” or “5
terminate”. Use the MODE button to select any parameter L, Leq, LE, Lmax or Lmin.
9. When the measurement time set in step 2 has elapsed, the measurement terminates
automatically.
10. Terminate the measurement earlier by pressing the PAUSE/CONT button, “ ” will
appear on the display. Press PAUSE/CONT to resume measuring.
11. Press the START/STOP button to stop measuring, the “ 5” mark will appear on the
display.
12. Press the MODE button to display the LAeq , LAE or other parameter value.
Note: In this measurement mode, the frequency weighting, time weighting and SLM/ 1/1/
1/3 mode cannot be changed.
Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176
FAX [phone] - TestEquipmentDepot.com

Model 407790 Ver. 1.1 7/02L
13
Datalogging
The 407790 has an automatic and a manual datalogging function. Stored measurement results
can be displayed by pressing the RECALL button.
Manual Datalogging (1024 data sets)
1. Set the power switch to ON.
2. Use the SLM/ 1/1/ 1/3 button to select the desired SLM, 1/1 or 1/3 octave band sound
pressure level measurement screen.
3. Press the MEMORY button to enter to memory mode; the display shows M [0001] which is
the first data record address number.
70
[ 1 / 1 OCT ] 01 / 07 / 27 14:26:39
31.5Hz
50
30
40
60
2k500125 8k L W
L
FAST
dB
90
80
100
WA 75.2 dB
4. Press the STORE button and one set of data will be stored in the [0001] memory
address location. The address counter is incremented by one.
5. Repeat the above steps to store additional data.
6. Press the MEMORY button again to exit the memory mode.

Model 407790 Ver. 1.1 7/02L
14
Reading from memory
1. Press the MEMORY button to access the memory mode; the display will show M
[∗∗∗∗].
2. Press the RECALL button to recall data; the display will show R [∗∗∗∗] which is the
record number and the data value in memory. If there are no data records in memory
the RECALL button will not be active.
70
[ 1 / 1 OCT ] 01 / 07 / 27 14:26:39
31.5Hz
50
30
40
60
2k500125 8k L W
L
FAST
dB
90
80
100
WA 75.2 dB
3. Press the 2nd button, the 2ND annunciator in the upper left of the screen will display.
4. Press the
Cursorkey to select the memory address of the data to be viewed.
5. In the 1/1 or 1/3 octave band screen, Press the 2nd button to remove the 2nd
annunciator, then press the Cursorbutton; the frequency and level values for the
desired data points will display.
6. Press the 2nd button to remove the 2nd annunciator.
7. Press the RECALL button to exit the recall mode.
8. Press the MEMORY button to exit the memory mode.

Model 407790 Ver. 1.1 7/02L
15
Automatic Datalogging
First set the datalogging sampling rate (how often a reading is stored). When in the auto
datalogging mode, parameter editing is disabled.
1. Setting the sampling rate: The default value is “0” indicating that datalogging is disabled.
Press the 2nd button, then press the MEMORY button to select the sampling rate from
the following list: 0sec (No recording) 1sec3sec10sec30sec1min5min
8min 10min 15min30min 1hr8h62.5ms. For example: with the rate set to 1
second, the display will read: P [00:00:01].
70
[ 1 / 1 OCT ] 01 / 07 / 27 14:26:39
31.5Hz
50
30
40
60
2k500125 8k L W
L
FAST
dB
90
80
100
WA 75.2 dB
2. Press the 2nd button, the 2ND annunciator will disappear from the screen.
3. Use the SLM/ 1/1/ 1/3 button to select the desired SLM, 1/1 or 1/3 octave band sound
pressure level measurement screen.
4. Set the preset measurement period (explained above in section X).
5. Press the MEMORY button to enter the memory mode; the upper portion of the LCD
will display “M [∗∗∗∗]”.
6. Press the START/STOP button, automatic datalogging will begin. The upper portion of
the screen will display “S Auto” and the “” annunciator.

Model 407790 Ver. 1.1 7/02L
16
70
[ 1 / 1 OCT ] 01 / 07 / 27 14:26:39
31.5Hz
50
30
40
60
2k500125 8k L W
L
FAST
dB
90
80
100
WA 75.2 dB
CAUTION: While automatic datalogging, parameter editing is disabled.
7. When the preset measurement time has elapsed (or the internal memory fills up to
maximum capacity) press the PAUSE/CONT button or press the START/STOP button,
to end the auto datalogging session.
8. To retrieve the stored data, use the PC interface utility.

Model 407790 Ver. 1.1 7/02L
17
Erase memory data
1. When the instrument memory is full, the FULL annunciator appears in the upper right
hand corner of the screen.
[ SLM ] 01 / 07 / 27 14:26:39
A
L
30 80
FAST dB
130
ID No: 00001358 Ver: 0.10
SOUND LEVEL METER
1/1 & 1/3 Octave Band
Real-Time Analyzer
Self-Testing......OK!!
ALL Memory are Erased !!
2. Turn off the meter, then press and hold down the STORE and the
RECALL buttons together. Turn on the meter and when the display shows “ALL
Memory Erased!” release the keys.
Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176
FAX [phone] - TestEquipmentDepot.com