Iso-Tech SLM 52N Instruction Manual

Instruction Manual

SLM 52N

Sound Level Meter

FREN

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CONTENTS

Title Page

1. INSTRUMENT CARE.....................................................................................1

2. FEATURES.....................................................................................................2

3. MEASUREMENT PARAMETERS..................................................................2

4. SPECIFICATIONS..........................................................................................2

5. CONTROLS AND FUNCTIONS.....................................................................9

6. DISPLAY DESCRIPTION............................................................................. 11

7. PREPARATION FOR USE...........................................................................12

8. CALIBRATION PROCEDURE.....................................................................14

9. MEASUREMENT PROCEDURE..................................................................14

10. STORE OPERATIONS...............................................................................15

11. OUTPUT CONNECTORS...........................................................................16

12. ADJUSTMENT DATA FOR CALIBRATOR (B&K TYPE 4226 PRESSURE

MODE)........................................................................................................16

13. TYPICAL INSTRUMENT FREQUENCY RESPONSE AT 0° INCIDENCE.16

14. TYPICAL FREQUENCY RESPONSE DUE TO CASE REFLECTIONS AT 0°

INCIDENCE.................................................................................................17

15. TYPICAL FREQUENCY RESPONSE OF 65mm WINDSCREEN AT 0°

INCIDENCE ................................................................................................17

16. DIRECTIONAL CHARACTERISTICS OF THE COMPLETE INSTRUMENT

..........................................................................................................................18

17. APPENDIX A FREQUENCY WEIGHTING NETWORK.............................20

18. APPENDIX B RMS DETECTION CIRCUIT AND TIME WEIGHTING.......21

19. APPENDIX C INFLUENCE OF BACKGROUND NOISE ..........................23

EN-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 sulphur content, gases and stored

chemicals, as this may damage the delicate microphone and sensitive electronics.

 Always turn the instrument off after use. Remove the batteries from the instrument if

it is not to be used for a long 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 any solvents, alcohol or cleaning
agents.

EN-2

2. FEATURES

The ISO-TECH SLM 52N Sound Level Meter complies with the requirements of
IEC 61672-1: 2002 standard for a Class 2 instrument.

The instrument contains several features which permit sound level measurements
under a variety of conditions.

Features include:

 Ease of use.
 Easy to read large display.
 Five measurement ranges.
 Fast and Slow time weightings.
 A and C frequency weightings.
 Both AC and DC signal outputs are available from a single standard 3.5mm

coaxial socket suitable for use with a frequency analyzer, level recorder, FFT
analyzer, graphic recorder, etc.

3. MEASUREMENT PARAMETERS

The following parameters are used on the instrument.

 LA → “A” frequency weighting sound pressure level
 LC→ “C” frequency weighting sound pressure level
 FAST→Fast time weighting
 SLOW→Slow time weighting
 max → Maximum time-weighted sound pressure level

The various settings depend on the condition the instrument was in before it was last
turned off.

4. SPECIFICATIONS

 Specifications apply to Model SLM 52N fitted with Microphone model MC-21 and

Microphone Preamplifier model AP-21



Applicable standards:

IEC61672-1: 2002 Class 2

IEC60651: 1979 Type 2
ANSI S1.4: 1983 Type 2

EN-3



Measurement functions:

•

Main processing functions

Sound level: Current time-weighted sound pressure level A or current time­weighted sound pressure level C

Maximum time-weighted sound pressure level A or Maximum time-weighted
sound pressure level C

•

Total range

: 30 to 130dB A & C weighted

•

Max. measurement level

: 130dB

•

Self-generated noise level:

Typical values at 23℃ using the nominal microphone equivalent capacitance of 27pF

(30-90dB range)

Weighting Electrical Total

“A” 22.7dB 26.1dB
“C” 21.8dB 29.5dB

Linearity operating range

: A-weighted, 1000Hz, 60dB dynamic range.

Total linear operating range:

In accordance with IEC 61672-1, A-weighted, 1000Hz: 30dB to 130dB.

Level range selection

:

5 ranges in 10dB steps 30 to 90dB , 40 to 100dB

50 to 110dB , 60 to 120dB
70 to 130dB

LINEAR OPERATING RANGES (L.O.R.)
RANGE: 30 – 90 dB. Test starting point 64 dB for all weightings and frequencies except

31.5Hz A-weighted, for which the starting point is 44 dB.

FREQUENCY
Hz

WEIGHTING L.O.R.

dB

WEIGHTING

L.O.R.

dB

31.5 A 36.1 – 50.6 C 39.5 – 87.0
1000 A 36.1– 90.0 C 39.5 – 90.0
4000 A 36.1 – 90.0 C 39.5 – 89.2
8000 A 36.1 – 88.9 C 39.5 – 87.0

RANGE: 40 – 100 dB. Test starting point 74 dB for all weightings and frequencies except

31.5Hz A-weighted, for which the starting point is 54 dB.

FREQUENCY
Hz

WEIGHTING L.O.R.,

dB

WEIGHTING

L.O.R

dB

31.5 A 40.0 – 60.6 C 40.0 – 97.0
1000 A 40.0 – 100.0 C 40.0 – 100.0
4000 A 40.0 – 100.0 C 40.0 – 99.2
8000 A 40.0 – 98.9 C 40.0 – 97.0

EN-4

RANGE: 50 – 110 dB. Test starting point 84 dB for all weightings and frequencies except

31.5Hz A-weighted, for which the starting point is 64 dB.

FREQUENCY
Hz

WEIGHTING

L.O.R

dB

WEIGHTING

L.O.R

dB

31.5 A 50.0 – 70.6 C 50.0 – 107.0
1000 A 50.0 – 110.0 C 50.0 – 110.0
4000 A 50.0 – 110.0 C 50.0 – 109.2
8000 A 50.0 – 108.9 C 50.0 – 107.0

RANGE: 60 – 120 dB. Test starting point 94 dB for all weightings and frequencies except

31.5Hz A-weighted, for which the starting point is 74 dB.

FREQUENCY
Hz

WEIGHTING

L.O.R.

dB

WEIGHTING

L.O.R.

dB

31.5 A 60.0 – 80.6 C 60.0 – 117.0
1000 A 60.0 – 120.0 C 60.0 – 120.0
4000 A 60.0 – 120.0 C 60.0 – 119.2
8000 A 60.0 – 118.9 C 60.0 – 117.0

RANGE: 70 – 130 dB. Test starting point 104 dB for all weightings and frequencies
except 31.5Hz A-weighted, for which the starting point is 84 dB.

FREQUENCY
Hz

WEIGHTING

L.O.R.

dB

WEIGHTING

L.O.R.

dB

31.5 A 70.0 – 90.6 C 70.0 – 127.0
1000 A 70.0 – 130.0 C 70.0 – 130.0
4000 A 70.0 – 130.0 C 70.0 – 129.2
8000 A 70.0 – 128.9 C 70.0 – 127.0

Frequency range

:

Overall characteristics including microphone: 31.5 to 8000Hz

Frequency weighting: A,

meets the requirement of IEC 61672-1 for class 2

“A” weighting.

C,

meets the requirement of IEC 61672-1 for class 2

“C” weighting.

Time weighting (RMS detection): Fast

, according to IEC 61672-1 class 2.

Slow

, according to IEC 61672-1 class 2.

EN-5

•

Reference conditions:

Type of the acoustic field:

Free

Reference sound pressure level:

94.0dB (related to 20µPa)

Reference level range:

60 to 120dB

Reference frequency:

1000Hz

Reference temperature:

+23

℃

Reference relative humidity:

50%RH

Reference static pressure:

101.325 kPa

Reference incidence direction:

Perpendicular to the front of the microphone

diaphragm.

•

Calibration:

Acoustic using calibrator ISO-TECH SLC 1356, B&K 4231 or equivalent.

Calibration check frequency is 1000Hz.

Nominal calibration level for the free field:

94.1dB

Nominal calibration level for the diffuse field:

94.0dB

•

Frequency for acoustic testing:

8000Hz

.

•

Warm-up time:

≦

2min

•

Sampling interval:

Bar graph indication → 125 ms approx.
Numeric indication → 1 sec approx.

•

Microphone equivalent electrical impedance (electrical input device) :

Replace

the microphone capsule with a series capacitance of 27pF +/- 3pF



Microphone:

•

Model:

MC-21

•

Nominal diameter:

1/2 inch electret condenser type

•

Sensitivity:

-37dB (0dB = 1V/Pa)

•

Frequency response:

31.5Hz to 8000Hz

•

Capacitance:

27pF

•

Reference direction and position:

Perpendicular to the front of the microphone

diaphragm at its geometric centre.

•

Maximum input sound level:

131dB at microphone for no damage.

•

Operating temperature:

-10°C to +50°C

•

Temperature coefficient:

Approx. 0.008dB/°C at 1000Hz

•

Dimensions:

13.2dia x 14mm

EN-6

Frequency Response

+5

-5

20 50 100 200 500 1000 2000 5000 10000 20000 (Hz)

(

dB)

0

Freq

units

31.5
Hz

63

Hz

125

Hz

250

Hz

500

Hz

1000Hz2000Hz4000Hz8000

Hz

dB +0.6 +0.8 +0.2 +0.0 0.0 0.0 +0.8 +1.3 +3.0

Typical free-field response 0°°°° incidence

2

0

-

2

0

-10

0

1

0

2

0

(

d

B

)

5

0

1

0

0

2

0

0

5

0

0

1

0

0

0

2

0

0

0

5

0

0

0

1

0

0

0

0

2

0

0

0

0

(

H

z

)

Freq

units

31.5
Hz

63

Hz

125

Hz

250

Hz

500

Hz

1000Hz2000Hz4000Hz8000

Hz

dB +0.1 +0.4 0.0 +0.5 -0.2 0.0 +0.2 0.0 -0.5

Typical diffuse-field response for random incidence



Preamplifier:

•

Model:

AP-21

•

Input impedance:

470MΩ

•

Output impedance:

550Ω at 1000Hz

•

Maximum input voltage:

2.828V peak-to-peak at electrical input for no damage.

•

Measuring input (viewed from top of instrument):

A: ground
B: ground
C: +10V
D: signal input
E: N.C.