User's Guide Digital Sound Level Meter Model 407740 Introduction Congratulations on your purchase of the Extech 407740 Digital Sound Level Meter. This device measures sound in decibels (dB). Useful features include A/C Weighting, Fast/Slow Response Time, and Maximum Reading HOLD. Careful use of this meter will provide years of reliable service. 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 (781) 890-7440 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 issued before 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. Specifications Display 2000 count multi-function LCD Input Signal Range ‘A’ Weighting: 30 to 130dB ‘C’ Weighting: 30 to 130dB Response Time Fast: Response = 125ms; Slow: Response = 1s Resolution 0.1 dB Standards Compliance o o Accuracy (at 23 ± 5 C) ANSI and IEC Type 2 ±1.5dB at 1KHz (94dB) Frequency 31.5 to 8,000Hz Microphone Electric condenser microphone, 0.5" (12.7mm) Range Selector Switch 30 to 80dB, 50 to 100dB, 80 to 130dB External Calibrator Use Extech model 407744 or 407766 Analog Output Signal AC: 0.5Vrms (full scale of selected range) DC: 0.3 to 1.3VDC, 10mV/dB Analog output impedance 600 ohms Analog Output Terminal 3.5mm phone jack Operating Temperature 32 °F to 122 °F (0 °C to 50 °C) Operating Humidity Max. 90% RH (0° to 35°C) Power Supply 9V battery Dimensions / Weight 10 x 2.8 x 1.1” (255 x 70 x 28mm) / 10 oz. (280 g) Support Hotline (781) 890-7440 Tech support: Ext. 200; Email: [email protected] Repair/Returns: Ext. 210; Email: [email protected] Website: www.extech.com 2 Model 407740 version 1.6 8/05 Meter Description 1. Microphone 2. LCD Display 3. Calibration potentiometer 1 Note: Adjust pot only while using an acoustic Calibrator 2 4. Selector Switches 3 5. Maximum Hold reset button 4 6. Analog output jack The battery compartment and tripod mount are located on the rear of the instrument 5 6 Operation Powering the Meter and Configuring the Analog Output Slide the POWER switch to the ON (DC) or ON (AC) position. The (AC) or (DC) determines the type of signal present at the analog output jack. Basic Measurements Point the microphone toward the source of the sound to be measured. The meter can be held in hand or mounted on a tripod (tripod mount on rear of instrument). The meter will now display the sound level in dB. Selecting ‘A’ or ‘C’ Weighting Use the Weighting selector switch to select ‘A’ or ‘C’ frequency weighting. Use ‘A’ weighting to have the meter simulate the response of the human ear (the human ear boosts and cuts sound levels at specific points over the frequency spectrum). ‘A’ weighting is used for environmental measurements, OSHA regulatory testing, law enforcement, and workplace design. Select ‘C’ weighting for flat response measurements (the readout does not boost or dampen the measurement across the frequency spectrum). ‘C’ weighting is suitable for the operational maintenance and analysis of machinery, motors, pumps, engines, etc. Selecting FAST or SLOW response Use the RESPONSE switch to select Fast or Slow. The setting is determined by the application and any directives or standards related to the application. For example, most hearing conservation or OSHA related testing is done using the SLOW setting (with ‘A’ weighting). To capture quick sound peaks, however, use the FAST setting. Selecting the Measurement Range Select the measuring range using the ‘dB’ selector switch. If the high (▲) or low (▼) indicators appear on the display, select a lower range (for ▲) or higher range (for ▼). Maximum Hold Function Select MAX HOLD using the RESPONSE selector switch to capture the maximum dB level. The meter response will be set to FAST. The display will only display the highest reading in this mode. To reset the Maximum Hold display, press the black reset button on the bottom of the meter next to the analog output jack. Calibration Frequent calibration using an acoustic calibrator is recommended. Follow the instruction provided with the calibrator. 3 Model 407740 version 1.6 8/05 Battery Replacement The low battery indication (BAT) appears on the LCD when the 9V battery is nearing depletion. Reliable readings can be obtained for several hours after the first appearance of the low battery indication. To replace the battery, slide the battery compartment cover off the rear of the instrument and replace the 9V battery. Secure the cover before use. Reference Information Frequency Weighting Characteristics Frequency (Hz) A Weighting C Weighting Tolerance (IEC 651 Type 2) 31.5 -39.4dB -3dB ±3dB 63 -26.2dB -0.8dB ±2dB 125 -16.1dB -0.2dB ±1.5dB 250 -8.6dB 0dB ±1.5dB 500 -3.2dB 0dB ±1.5dB 1k 0dB 0dB ±1.5dB 2k +1.2dB -0.2dB ±2dB 4k +1dB -0.8dB ±3dB 8k -1.1dB -3dB ±5dB Typical A-Weighted Sound Levels dB 140 50HP Siren (100') 130 Jet takeoff (200') 120 110 Riveting machine 100 Subway (20') 90 Pneumatic drill (50') 80 Vacuum cleaner (10') 70 Large store 60 Small office 50 Night residential area 40 Whisper (5'0) 30 20 Chain saw Boiler room Freight train (100') Speech (1') Large Office Residence Sound studio 10 0 Threshold of hearing Calibration and Repair Services Extech offers repair and calibration services for the products we sell. Extech also provides NIST certification for most products. Call the Customer Service Department for information on calibration services available for this product. Extech recommends that annual calibrations be performed to verify meter performance and accuracy. Copyright © 2003 Extech Instruments Corporation All rights reserved including the right of reproduction in whole or in part in any form. 4 Model 407740 version 1.6 8/05