Extech Instruments 407790 User Manual

User Manual

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Real Time Octave Band Analyzer

Model 407790

99 Washington Street
Melrose, MA 02176

Phone [phone]
Toll Free 1-800-517-8431

FAST

L

W A

dB

100

90
80
70
60
50
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30

Hz 125

31.5 500

[ 1 / 3 OCT ] 01 / 07 / 27 14:26:39

75.2 dB

8k 2k L W

Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176

FAX [phone] - TestEquipmentDepot.com

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), L
(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:

Measurement Frequency range: 25Hz

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:

Frequency weighting: ‘A’, ‘C’, ‘P’ (Flat)

Time weighting (Response Time): Fast and Slow

Microphone: 1/2 inch electret condenser type

±1.5dB (ref 94dB @1kHz)

to

10 kHz

70dB (20 to 90dB, 30 to 100dB, 40 to 110dB, 50
to 120dB, 60 to 130dB

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Model 407790 Ver. 1.1 7/02L

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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 104

Storage Temperature/Humidity: 14 to 140

o

F (0 to 40℃); 10 to 90%RH

o

F (-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 Windows
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

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Model 407790 Ver. 1.1 7/02L

TM

Meter Description

Refer to the diagram below for the following descriptions.

1. Windscreen

9. AC analog output jack

2. Microphone

3. Display

4. Operation keys

5. Power switch

6. Calibration adjust knob

7. 6VDC adapter jack

8. DC 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

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Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176

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SOUND ANALYZER
1/1 & 1/3 OCTAVE BAND
IEC 651 IEC 804 TYPE 2
IEC 1260 CLASS2
ACCURACY : ¡Ó1.5dB

IEC LR14 1.5V X 4

Model 407790 Ver. 1.1 7/02L

FAX [phone] - TestEquipmentDepot.com

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.

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Model 407790 Ver. 1.1 7/02L

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”.

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Model 407790 Ver. 1.1 7/02L

Measurement Screens

1. Sound pressure level measurement screen

FAST

L

A

30 80

dB

130

[ SLM ] 01 / 07 / 27 14:26:39

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.

FAST

AL

dB

100

90
80
70
60
50
40
30

31.5 125Hz

[ 1 / 1 OCT ] 01 / 07 / 27 14:26:39

2k Hz

68.4 dB

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L W

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.

7

Model 407790 Ver. 1.1 7/02L

FAST

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dB

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[ 1 / 3 OCT ] 01 / 07/ 27 14:26:39

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 (L

)

A

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

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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
checks to establish instantaneous noise levels. SPL is defined by the logarithmic
equation:

: Instantaneous sound pressure level (SPL) is used for spot

SPL (in dB): 20 log

P

10

0P

Where P = rms measured sound pressure level

= rms reference sound pressure level (20µ Pa)

P

0

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. L

– Sound exposure level

E

L

measurements are almost identical to Leq measurements but normalised or

E

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 L

measurement either a preset

E

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.

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Model 407790 Ver. 1.1 7/02L

Instantaneous sound pressure level measurement (L

, LC, LP)

A

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...

FAST

L

A

30 80

[ SLM ] 01 / 07 / 27 14:26:39

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.

FAST

A

L

dB

100

90
80
70
60
50
40
30

500

125Hz 31.5

75.2 dBW

8k L W2k

[ 1 / 1 OCT ] 01 / 07 / 27 14:26:39

3. Use the FREQ WGHT button to select the desired L

FAST

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[ 1 / 3 OCT ] 01 / 07/ 27 14:26:39

, LC or LP frequency weighting

A

2k500125 8k L W

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.

10

Model 407790 Ver. 1.1 7/02L

FAST

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A

L

dB

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80
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60
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30

125Hz 31.5

500

75.2 dBW

WL8k2k

[ 1 / 1 OCT ] 01 / 07 / 27 14:26:39

and LE measurement

L

eq

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

•

3s

•

10s

•

30s

•

1min

•

5min

•

8min

•

Note: The setting will wrap around from 24h to 1s.

10min

•

15min

•

30min

•

1h

•

8h

•

24h

•

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Model 407790 Ver. 1.1 7/02L

FAST

L

A W 75.2 dB

dB

100

90
80
70
60
50
40
30

Hz 31.5 125 500 2k WL8k

[ 1 / 1 OCT ] 01 / 07 / 27 14:26:39

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 L

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, L

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 L

Aeq

, L

Note: In this measurement mode, the frequency weighting, time weighting and SLM/ 1/1/

1/3 mode cannot be changed.

, LC or LP frequency weighting

A

or other parameter value.

AE

, Lmax or Lmin.

E

Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176

FAX [phone] - TestEquipmentDepot.com

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.

FAST

100

L

dB

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30

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WA 75.2 dB

2k500125 8k L W

[ 1 / 1 OCT ] 01 / 07 / 27 14:26:39

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.

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Model 407790 Ver. 1.1 7/02L

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.

FAST

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L

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30

31.5Hz

WA 75.2 dB

2k500125 8k L W

[ 1 / 1 OCT ] 01 / 07 / 27 14:26:39

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.

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Model 407790 Ver. 1.1 7/02L

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].

FAST

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L

dB

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31.5Hz

WA 75.2 dB

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[ 1 / 1 OCT ] 01 / 07 / 27 14:26:39

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.

∗∗∗∗

]”.

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Model 407790 Ver. 1.1 7/02L

FAST

L

dB

100

90
80
70
60
50
40
30

31.5Hz

WA 75.2 dB

2k500125 8k L W

[ 1 / 1 OCT ] 01 / 07 / 27 14:26:39

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.

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Model 407790 Ver. 1.1 7/02L

Erase memory data

1. When the instrument memory is full, the FULL annunciator appears in the upper right

hand corner of the screen.

ID No: 00001358 Ver: 0.10

FAST

L

A

30 80

dB

130

[ SLM ] 01 / 07 / 27 14:26:39

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.

ALL Memory are Erased !!

SOUND LEVEL METER
1/1 & 1/3 Octave Band
Real-Time Analyzer

Self-Testing......OK!!

Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176

FAX [phone] - TestEquipmentDepot.com

17

Model 407790 Ver. 1.1 7/02L