Extech Instruments SL120 User manual

User's Manual

Sound Level Monitor

Model SL120

Meets ANSI and IEC Type 2 Sound Level Meter Standards

Settable High Limit with large OVER indication and Alarm Output

Wall or Desk mountable

Extra large LCD display with bargraph

Maximum level display with time stamp

Optional alarm kit drives remote over limit indicators.

Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176 - FAX 781.665.0780 - TestEquipmentDepot.com

Version 1.2 9/05

Introduction

Congratulations on your purchase of the Extech SL120 Sound Level Monitor. Designed for

wall mount, desk, tripod mount or hand held operation, this meter meets ANSI and IEC

Type 2 Sound Level Meter standards. Included is a High Limit Set Point with a large OVER

indication when the set level is exceeded. An Alarm Output can be used in conjunction with

the optional Alarm Module Kit to power a larger or a remote indicating device such as a

“QUIET” sign. Professional features include programmable A/C Weighting and Fast/Slow

Response time, Max Memory with time stamp, and a Clock display. The microphone can

be rotated 180 degrees to accommodate any meter location or it can be placed at a remote

location using the optional Remote Microphone Cable. A programmable ON/OFF time

extends battery life to 30 days when programmed 8 hours per day. Careful use of this

meter will provide years of reliable service.

Specifications

Applicable standards Meets IEC 60651-1979 and ANSI S1.4 1983 Type 2

SLM standards

Display 4.6” x 3.125” multifunction LCD

Frequency bandwidth 31.5 Hz to 8 KHz

Microphone 0.5” Electret Condensor Microphone (remoteable)

Measurement ranges 30 to 80dB, 60 to 110dB, 80 to 130dB

Frequency weighting ‘A’ and ‘C’ (Programmable)

Response time Fast (125ms) / Slow (1s) (Programmable)

Resolution 0.1dB

Max Hold Maximum reading is displayed with time

Alarm output 3.5mm Mono Phone Plug, Maximum: 3.4mA @ 5 Vdc,

Minimum Output Voltage: 2.5 Vdc

Limit range 30 to 130dB

Under range indication “- - -“

Over range indication “OL”

Power 8 AA Batteries; optional AC adaptor (9V@350ma)

Battery life 240hrs continuous (approx); 30 days @ 8hrs/day

Operating temperature 32 to 122oF (0 to 50oC)

Operating humidity Less than 80% RH

Dimensions / Weight 8.75x7.1x1.25" / 0.63 lbs. (22x18x3.2mm / 285g)

Version 1.2 9/05

30-80

LIMIT

80-130

60-110

123456

Meter Description

1. Microphone

2. Over Limit Display

3. Bargraph

4. dB display

5. OFF/ON/AUTO switch

6. Clock display

7. Max level display with time stamp

8. Set limit

9. MAX RESET button

Rear Panel

1. Range select switch

2. Time set buttons

3. Limit set buttons

4. Calibration adjustment

5. A/C select button

6. F/S select button

Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176 - FAX 781.665.0780 - TestEquipmentDepot.com

Version 1.2 9/05

Sound Level Monitor Operation

Initial Configuration

1. Install 8 AA batteries

2. Setting the TIME

a) Press and Hold the Time SET button until the hours display

begins to flash.

b) Press the Time up arrow button until the hour is set.

c) Press the SET button. The minutes display will flash. Adjust as needed.

d) Press the SET button to step through and the arrow button to adjust;

Time of day Hour

Time of day Minutes

Time of day AM / PM / 24 Hour

Year

Month

Day

Auto ON Hour

Auto ON Minutes

Auto OFF Hour

Auto OFF Minute

A/C Frequency Weighting

Change the Frequency Weighting by pressing the 'A/C' button. The 'A' or 'C' icon will

appear on the display.

With ‘A’ weighting selected, the frequency response of the meter is similar to the response

of the human ear. ‘A’ weighting is commonly used for environmental or hearing

conservation programs such as OSHA regulatory testing and noise ordinance law

enforcement. ‘C’ weighting is a much flatter response and is suitable for the sound level

analysis of machines, engines, etc.

Most noise measurements are performed using 'A' Weighting and SLOW Response.

Slow/ Fast Response

Press the button to select Fast or Slow response as desired. F or S will appear in the

bottom of the LCD display.

Select FAST to capture noise peaks and noises that occur very quickly. Select the SLOW

response to monitor a sound source that has a consistent noise level or to average quickly

changing levels.

Select Slow response for most applications.

Range Selection

Slide the Range switch to the 30-80, 60-110 or the 80-130 position.

The selected range will be indicated on the LCD bargraph. If the

measured dB level exceeds the range selected “OL” will be

displayed. If the measured dB level is below the selected range “- - -“ will be

displayed.

Normally, select the range in which the upper dB level is greater than any

expected sound pressure level. The 60 to 110dB range is the most commonly

used range. Use the 30 to 80dB range in quieter areas such as offices and classrooms.

Note: When the range is changed the Max display may indicate an overload “OL”. Press

the MAX RESET button to clear the MAX display.

Version 1.2 9/05

Over Limit Set

Press the up or down LIMIT arrow buttons to set the OVER limit

level as displayed on the LCD. If the measured dB level exceeds

the set limit, the indication will appear in the display and the

over limit signal will appear at the alarm output connector. The

display indication and output signal will remain active as long as the

sound pressure level exceeds the set limit.

MAX Hold

The MAX display indicates and holds the highest dB level measured

since the meter was turned on or since the Max Reset button was

pressed. The time and date of the max reading is also displayed.

To clear the display and start a new measurement session, press the

front panel MAX RESET button. If the measured level exceeds the maximum for the range

selected the MAX display will indicate “OL” (overload).

Programmable OFF/ON/AUTO time

The meter is powered by 8 AA batteries or via an AC adaptor for permanent installations.

Continuous battery life is approximately 240 hours (10 days). By programming the ON/OFF

time, the battery life can be greatly extended (30 days assuming an 8 hour day). The ON

and OFF times are programmed as described in the initial configuration

paragraph. The meter will operate continuously with the power switch in

the ON position. The ON/OFF time will be controlled by the meter when

the power switch is set to the AUTO position.

Calibration

The sound level meter should be calibrated on a regular basis to assure that the meter’s

performance and microphone sensitivity has not change. Some operational directives

require daily calibration checks (OSHA). Extech offers several acoustic calibrators to

perform the calibration.

1. Set the meter to the 60 to 110dB or 80 to 130dB range.

2. Place the external calibrator over the Sound Level

Monitor's microphone and turn the Calibrator on.

3. The meter should read close to the calibrator's dB output

level. Typical Calibrator output levels are 94dB and 114dB.

4. If the meter is within ± 0.2 dB of the calibrator’s output, no

adjustment is necessary.

5. Adjust the calibration pot on the rear of the meter to the

proper level.

Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176 - FAX 781.665.0780 - TestEquipmentDepot.com

Version 1.2 9/05

Meter Placement

The meter can be used Handheld, Wall mounted, Desk mounted or Tripod mounted. For

wall mount operation, orient the microphone perpendicular to the wall to minimize the

affect of acoustic reflections. For desk mounting, extend the rear legs and lock in place

with the hinged locks. The tripod mounting nut is located on the bottom of the unit.

Remote Microphone (optional)

The optional 15’ remote microphone cable can be used to place the microphone in one

location while viewing the dB levels and/or generating a high limit alarm at another

location. To remove the microphone, unscrew the holding collar and lift the microphone off

the connector. The extension cable can then be plugged into the matching connectors.

Calibration should be performed after the cable is installed.

Alarm Output (optional)

The alarm output drives the optional Remote Alarm Relay Module (cable and relay) when

the LIMIT set point is exceeded. The relay module can be used to power external warning

signs, “QUIET” signs or other indicating devices when the sound level is higher than the

programmed limit. Refer to the manual supplied with the module for connection

information.

HEARING

PROTECTION

REQUIRED

AC or DC Power

Relay Module

Indicating Device

Note: For up-to date information on this product, optional accessories and literature, call

or go to www.extech.com.

Version 1.2 9/05

20 50 100 2k1k 5k 10k 20k

200 500

-20

-30

-40

-50

-10

Frequency (Hz)

Weighting Response Curves

Measurement Considerations

1. Use a windscreen (not included) to cover the microphone in windy conditions.

2. Calibrate the meter often, especially if the meter has been idle for a long period of time.

3. Do not store/operate the meter in areas of high temperature or humidity.

4. Keep the meter and the microphone dry.

5. Avoid severe vibration when using the meter.

6. Remove the battery when the meter will be stored for long periods of time.

Frequency Weighting curves

OSHA permissible levels Permissible Noise Exposure Limits

Duration per Day (hours) Sound Level db(A) Slow response

16 85

8 90

6 92

4 95

3 97

2 100

1-1/2 102

1 105

1/2 110

¼ or less 115

Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176 - FAX 781.665.0780 - TestEquipmentDepot.com

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