Extech Instruments 407790A User manual

User Manual
Real Time Octave Band Analyzer
Model 407790A
Additional User Manual Translations available at www.extech.com

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Table of Contents
TABLE OF CONTENTS ..........................................................................................2
1. INTRODUCTION................................................................................................3
1.1 Instrument Care ............................................................................................4
1.2 Features........................................................................................................5
2. DESCRIPTIONS ................................................................................................6
2.1 Meter Description..........................................................................................6
2.2 Operation Buttons.........................................................................................8
2.3 Display Screen............................................................................................10
2.4 Analysis screen...........................................................................................12
2.5 Numeric Display screen..............................................................................13
3. MEASUREMENT PREPARATION AND SETUP ............................................15
3.1 Setting the Date and Time ..........................................................................15
3.2 SD Memory Card ........................................................................................17
3.3 Setting the Backlight Auto Off time .............................................................17
3.4 Sub Channel Settings.................................................................................18
3.5 Selecting the Lmax/Lmin type ....................................................................19
3.6 Comparator Output Operation ....................................................................20
3.7 Trigger Mode Setup and Operation ............................................................23
4. MEASUREMENTS...........................................................................................27
4.1 Sound Level Measurements.......................................................................27
4.2 SEL, Leq, Lmax, Lmin, LN Measurements.................................................28
4.3 Sound Level and Octave Band Analysis Measurement .............................30
4.4 Sound Band - Leq, SEL, Lmax, Lmin and LN Analysis Measurement .......32
5. STORING DATA TO MEMORY .......................................................................34
5.1 Manual Memory Storage ............................................................................34
5.2 Recalling Manually Stored Data .................................................................37
5.3 Erasing Manually Stored Data....................................................................39
5.4 Auto 1 Memory Storage..............................................................................40
5.5 Auto 2 Memory Storage..............................................................................44
5.6 Erasing Auto Stored Data ...........................................................................45
6. SOFTWARE DOWNLOAD AND INSTALLATION ..........................................47
7. SOUND PRESSURE LEVEL - TECHNICAL NOTES .....................................48
8. CALIBRATION.................................................................................................49
9. SPECIFICATIONS ...........................................................................................50
10. TWO-YEAR WARRANTY................................................................................53

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1. Introduction
Congratulations on your purchase of the Extech 407790A 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 analyses. The 407790A offers five measurement
parameters: SPL (Sound Pressure Level), Leq (Equivalent Continuous Sound Pressure
Level), SEL (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 407790A software and USB cable. This meter permits
choice of ‘A’, ‘C’, or Flat ’Z’ weighting and Slow / Fast /impulse 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.

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1.1 Instrument Care
Do not attempt to remove the mesh cover from the microphone as this will cause damage
and affect the accuracy of the instrument.
Protect the instrument from impact. Do not drop it or subject it to rough handling.
Transport it in the supplied carrying case.
Protect the instrument from water, dust, extreme temperatures, high humidity and direct
sunlight during storage and use.
Protect the instrument from air with high salt or sulfur content, gases and stored chemicals,
as this may damage the delicate microphone and sensitive electronics.
Always switch the instrument off after use. Remove the batteries from the instrument if it
is not to be used for a long period of time. Do not leave exhausted batteries in the
instrument, as they may leak and cause damage.
Clean the instrument only by wiping it with a soft, dry cloth or, when necessary, with a cloth
lightly moistened with water. Do not use solvents, abrasives, alcohol or cleaning agents

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1.2 Features
The Sound Level Meter complies with the requirements of IEC 61672-1:2003 standard for a
Class 2 instrument. See specifications section for more applicable standards that apply to this
meter.
1/1 octave band analysis from 31.5Hz to 8kHz
1/3 octave band analysis from 25Hz to 10kHZ
Can perform 1/1 and 1/3 octave band analysis simultaneously
4GB Micro SD card
USB interface
Datalogging function
AC/DC signal output available for level and graphic recorder
Comparator output function
External trigger input function
Real time clock with calendar
Main channel (sound meter, analyzer mode)
Sub Channel (sound level meter mode)
The 407790A allows the following quantity measurements.
Simultaneous measurements of all items with selected time weighting and frequency
characteristics.
Sound level Lp
Equivalent continuous sound Leg
Sound exposure level SEL
Maximum sound level Lmax
Minimum sound level Lmin
Percentile sound level LN (L05, L50, L90, L95) calculated from Lp
Frequency rating A, C, Z
Time weighting
Main Channel Fast, Slow, 10ms, impulse
Sub Channel Fast, Slow, 10ms, impulse
Safety Symbol: Complies with EMC

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2. Descriptions
2.1 Meter Description
Refer to the diagram below for the following descriptions.
1. Windscreen
2. Microphone
3. Display
4. Operation keys
5. 6VDC adapter jack
6. DC analog output jack
7. AC analog output jack
8. Comparator output jack
9. Trig IN jack
10. Micro SD card slot
11. Power switch
12. Hand strap
13. USB port
14. Battery compartment
15. Tripod mounting screw

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2.2 Operation Buttons
START/STOP button
Press to start or stop for recording the sound pressure measurement.
PAUSE/CONT button
Press to temporarily pause ( ) a measurement) or resume () measurement.
M button
Press to scroll through and select different processing modes.
LEVEL 
Press to select the level range for measurement. The following five settings are available.
20 to 90 dB, 20 to 100 dB, 20 to 110 dB, 30 to 120 dB, 40 to 130 dB.
GRP/ NUM button
Press to switch between graph and numeric display for Octave measurements.
SLM 1/1 1/3 button
Press to switch to select the sound level meter display and analysis screen.
(SLM, 1/1, 1/3, 1/1&1/3)
MENU
Press to enter menu screen to setup various menu parameters. Press again to close the
menu.
R button
Start or stop the auto Record process or press to manually store the measurement data

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into memory.
/ 
Press to move the octave frequency band marker during frequency analysis.

+
/

-
Press to select and set items in various menu screens. Holding the buttons down will cause
faster scrolling.
FREQ WEIGHT TIME button
The FREQ WEIGHT selects the frequency weighting for the main channel. “A” weighting (A),
“C” weighting (C), and flat frequency response (Z).
The TIME WEIGHT selects the time weighting function for the main channel. (F, S, 10ms, I)
Fast: 125ms; Slow: 1000ms; 10ms; Impulse: 35ms
Note: The frequency and time weighting for the sub channel can be selected by accessing
the menu screen.
button (Backlight/Enter)
Backlight powers on the display backlight. Press the button again to turn backlight off.
When automatic Backlight Off function is selected from the menu screen, the backlight will
turn itself off automatically after the preset time.
Enter button will finalize a setting of an item in a menu or any other setting.

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2.3 Display Screen
1. Mode of analysis: Indicates the condition of the display screen.
SLM: Sound level meter display
1/1 OCT: Octave band analysis screen
1/3 OCT: 1/3 Octave band analysis screen
1/1 and 1/3 OCT: Simultaneous octave and 1/3 octave band analysis screen
2. Measurement in progress: When a measurement recording is in progress or during auto store
the symbol flashes. During measurement pause the symbol is displayed on the screen.
3. USB Link Status: Shows if the USB is enabled or disabled.
4. Trigger Mode: Controls the measurement and memory auto store start behavior. Available
modes are: Level 1 (LV1), Level 2 (LV2), EXT (EXT), and time (TIME).
5. Elapsed Time: Displays the elapsed time in seconds during processing and storing memory.
6. Memory: Displays the selected memory for storing data.
FL: The data will be stored in the internal memory of the meter.
Sd: The data will be stored on the micro SD card
Mode of analysis
Measurement in progress symbol
USB link status
Trigger mode
Elapsed time
Memory
Store mode
Address
Level range
Overloadindication
Subchannelleveldisplay
Sub channel
Time weighting
Frequencyweighting
Current time
Current date
Comparator ON
Auto store full indication
Manual store full indication
Power
status
Mainchannellevel
display
Time weighting
Main channel
Frequencyweighting
Underrangeindication
Bar graph

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7. Store mode: Displays the selected mode for storing data in memory
M: Manual store
A: Auto store
8. Address: Displays current number of data surveys stored in memory.
9. Bar graph: Displays the sound level as a bar graph. (The display is updated every 100ms)
10. Level range: Displays the upper and lower limit of the bar graph. Can be changed with the
LEVEL button.
11. Under-range indication: When a signal is under-range the UN symbol will appear on the
screen. Use the LEVEL button to decrease the level range setting. If processed data is
under-range the UN indication will remain on the screen until the next processing
measurement is started.
12. Overload indication: When a signal overload is detected, the screen will display OV for at
least 1 second. Use the LEVEL button to increase the level range setting. If processed
data is over range the OV indication will remain on the screen until the next processing
measurement is started.
13. Main channel frequency weighting: Indicates the main channel frequency characteristic. A:
A-weighting, C: C-weighting, Z: Z-weighting (flat response)
14. Main channel time weighting: Indicates the main channel time weighting characteristic.
F: Fast (125ms), S: Slow (1000ms), τ: (10ms), I: Impulse (35ms)
15. Main channel level display: Displays the measured sound level in the main channel.
(The display is updated every second).
16. Sub channel frequency weighting: Indicates the sub channel frequency weighting
characteristic. A: A-weighting, C: C-weighting, Z: Z-weighting (Flat response).
The sub channel frequency weighting can be set from the menu screen.
17. Sub channel time weighting: Indicates the sub channel time weighting characteristic.
F: Fast (125ms), S: Slow (1000ms), τ: (10ms), I: Impulse (35ms)
18. Sub channel level display: Shows the measured sound level in the sub channel.
(The display is updated every second)
19. Power status: When operating the meter on battery power the yellow segments will
decrease as the battery power drains. When the segment starts to flash, replace batteries.
20. Manual store full: When the manual stored memory is full, the MFul symbol is displayed.
The manual data store capacity is 250 sets.
21. Auto store full: When the auto store memory is full, the AFul symbol is displayed. The auto
store capacity is 250 blocks.
22. Comparator ON: When the comparator function has been set to ON and a signal exceeds
the comparator output jack, the indicator Cmp will appear on the display. A signal will
output from the comparator output jack on the side panel (open collector).
23. Current date: Displays the current date
24. Current time: Displays the current time

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2.4 Analysis screen
An example for the 1/1 & 1/3 OCT analysis screen is shown below.
Use the and buttons to move the cursor to the target frequency band.
1/1 and 1/3 analysis screen

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2.5 Numeric Display screen
Example for 1/1 OCT, 1/3 OCT, and 1/1 & 1/3 OCT analysis screen are shown below.
Use the and buttons to view a frequency that is not displayed.

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3. Measurement Preparation and Setup
1. Battery installation: Remove the rear battery cover as shown below and insert (4) 1.5V ‘C’
size alkaline batteries. Take care to observe battery polarity. Replace the battery cover.
2. Battery replacement: When the battery voltage drops below operating voltage,
battery symbol flashes on the display.
3. AC adaptor connection: Insert the adaptor in the DC 6V jack on the side panel. When the AC
adapter is connected, the meter will be powered from the adapter even if batteries are
installed.
Notes:
To prevent the risk of damage, use only the factory supplied AC adapter.
To prevent the risk of battery leakage, remove the batteries from the meter when the meter is
not in use.
3.1 Setting the Date and Time
Date and time information is stored with each record saved. Set the date and time as follows:
1. Press power switch ON and wait until the measurement screen appears.
2. Press the MENU button. The menu list screen will display.
3. Press the

+
/

-
button to select “D) Date setting (Y/M/D)”and then press the enter 
button.
4. Press the

+
/

-
button to set the value. Press button to confirm.
5. Continue pressing the above buttons to scroll through and set each option for date and time.
The meter will continue to scroll through setup for date Y/M/D and then the time settings
h/m/s.
6. When the settings are correct, press the button to exit the setting mode. The clock will
start running with the new settings.
7. Press MENU button to return to the measurement screen.
Note: The clock has an error of about 1 minute per month. Before taking measurement, be sure
to check and set the time if required.
Date

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Time

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3.2 SD Memory Card
Measurement data can be stored on a removable SD memory card for later use.
Note: Power OFF the meter before inserting or removing the memory card.
Use only a 4GB micro SD card. Removing SD card or powering the meter off while data is storing
to the card can cause internal data to be destroyed.
1. Insert the card taking care to observe the correct orientation. Push the card in carefully,
until it is properly sealed.
2. To remove, push the card. The SD card with pop out and can be removed.
3.3 Setting the Backlight Auto Off time
1. Press the to turn the backlight on or off.
2. Press the MENU key to bring up the menu list screen.
3. Use the

+
/

-
key to select “Backlight Auto Off” then press the key.
4. Use the

+
/

-
key to select the automatic turn off time then press the key. Options
are: 30 seconds, 1 minute, 3 minutes or OFF (without automatic turn - off function).
5. Press MENU key to return to the measurement screen.
To turn the backlight off before the automatic turn - off time, press the key.

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3.4 Sub Channel Settings
To access the sub menu setting press the following buttons.
1. Press the MENU button to enter the menu list screen.
2. Use the

+
/

-
buttons to select “G). Sub Time Weight” then press button.
3. Use the

+
/

-
button to select the desired time weighting
F, S, τ(10ms) or I (Impulse 35ms), then press button.
4. Press the

+
/

-
buttons to select “H). Sub Freq Weight” then press button.
5. Press the

+
/

-
buttons to select the desired frequency weighting A, C or Z, then press 
button.
6. Press MENU button to return to the measurement screen.
Note: There is no frequency analysis function for the sub channel. Only the all - pass value is
measured.

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3.5 Selecting the Lmax/Lmin type
Band - (Band maximum/band minimum):
The analysis result applies to the point where the level for each frequency band was maximum
or minimum within the sampling period.
AP - (All-pass maximum/all-pass minimum):
The analysis result applies to the sub channel all-pass and band-pass level values taken at the
point where the all-pass level in the main channel was maximum/minimum within the
sampling period.
AP (S) - (All-pass maximum/all-pass minimum):
The analysis result applies to the band-pass level values (excluding the sub channel all-pass
levels) taken at the point where the all-pass level in the main channel was
maximum/minimum within the sampling period. The sub channel all-pass level is taken at
the maximum/minimum point within the sampling period, independently of the main
channel level.
1. Press the MENU button to enter the menu list screen.
2. Use the

+
/

-
buttons to select “I).Lmax/Lmin Type” then press button.
3. Use the

+
/

-
buttons to select the desired Band, AP or AP (S) type then press button.
4. Press MENU button to return to the measurement screen.
This setting is effective in SLM mode and Octave band analyzer mode.

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3.6 Comparator Output Operation
The comparator output is an open collector output that can be used to control external
equipment.
1. Press the MENU button to enter the menu list screen.
2. Use the

+
/

-
buttons to select “J). Comparator” then press button to display the
ON/OFF setting.
3. Press the

+
/

-
buttons to select “ON” then press button.
4. Press the

+
/

-
buttons again to select “1). Comparator Level”. Set the desired level
then press button. (Setting range 25 to 130dB, 1 - dB steps)
5. Follow the above steps to select “2). Comparator Band”. Set the band to desired level then
press button. (MAIN AP/31.5Hz/63Hz/…8kHz or 1/3 octave bands).
6. Press the MENU button to return to the measurement screen.
AP
AP