DIGITAL SOUND METER WITH JUMBO DISPLAY USER’S MANUAL DSM8925 Please read this manual carefully and thoroughly before using this product.
TABLE OF CONTENTS Introduction . . . . . . . . . . . . . . . . . . . . . . 3 Key Features . . . . . . . . . . . . . . . . . . . . . 4 What’s in the Box . . . . . . . . . . . . . . . . . 5 Product Overview . . . . . . . . . . . . . . 5 – 7 Setup Instructions . . . . . . . . . . . . . . . . . 8 Install Batteries . . . . . . . . . . . . . . . . 8 Operating Instructions . . . . . . . . . 8 – 15 Making Basic Measurements . . 8 – 9 Autoranging vs. Manual Ranging . . . . . . . . . . .
INTRODUCTION Thank you for purchasing General Tools & Instruments’ DSM8925 Digital Sound Meter with Jumbo Display. Please read this user’s manual carefully and thoroughly before using the instrument. The DSM8925 uses an integrated condenser microphone to measure the noise level of an environment or the loudness of a machine, typically in order to comply with health and/or safety rules. The meter has a range of 30 to 130 dB and an accuracy of ±2 dB.
Physical features of the DSM8925 include an analog output jack for connecting to a data logger or chart recorder, a tripod mounting socket, and an adjustment screw for calibrating the meter to a standard 94 dB input. The DSM8925 includes a wind shield ball and is powered by four “AAA” batteries (also included).
WHAT’S IN THE BOX The DSM8925 comes fully assembled in a box along with a wind shield ball, four “AAA” batteries and this user’s manual. PRODUCT OVERVIEW Figure 1 shows all of the controls, indicators and connectors on the front and right side of the DSM8925. Familiarize yourself with their positions and functions before moving on to the setup procedure. A B C J G H I D E F FRONT K RIGHT SIDE 1. The DSM8925’s controls, indicators and connectors A. Wind shield ball B. Microphone C.
F. REC—Enters/exits Recording mode G. RNG—Selects autoranging or manual ranging H. F/S—Selects fast or slow time response I. MAX HOLD button J. Calibration adjustment screw K. Analog output jack Figure 2 shows all text and icons that could appear in the display window at various times. 2.
FAST Meter is applying fast time weighting to inputs SLOW Meter is applying slow time weighting to inputs AUTO Meter is automatically choosing measurement range with best resolution MANU Meter is using user-selected measurement range BA Reserved for future use SPL Abbreviation of sound pressure level (the parameter measured) Meter’s battery is very low on charge and should be replaced A Meter is applying “A” frequency weighting to inputs C Meter is applying “C” frequency weighting to inputs dB Sound level u
SETUP INSTRUCTIONS INSTALL FOUR BATTERIES The meter’s battery compartment is accessible from the back of the unit. Use a Philips-head screwdriver to remove the one screw holding the cover in place. Then install the four included “AAA” batteries so their + and – ends match the images stenciled inside the compartment. Finally, replace the cover and secure it with the Philips-head screw. OPERATING INSTRUCTIONS MAKING BASIC MEASUREMENTS To begin, press the button to power on the meter.
To measure the loudness of a sound source, point the microphone at it. The meter’s default settings are autoranging on (enabling measurements from 30 to 130 dB), fast time weighting and “A” frequency weighting. When the meter is powered on, AUTO will appear on the left side of the display, with FAST on the top line and A on the right side. Following are procedures for changing each of these settings to suit the application. AUTORANGING VS.
The meter can display its results more quickly because it does not have to first determine which range to use. To exit Autoranging Mode and enter Manual Ranging mode, briefly press the RNG button on the front panel. Note that when you press the button, the text MANU replaces AUTO on the left side of the display. Also note that the Range Baseline above the left end of the bar graph no longer changes in response to louder or softer sounds, as in did in Autoranging mode.
digital display will show the letters LO or HI. If this happens often, consider switching back to Autoranging mode. To exit Manual Ranging mode and return to Autoranging Mode, press and hold the RNG button until the text AUTO replaces MANU on the left side of the display. TIME AND FREQUENCY WEIGHTING OPTIONS You can choose Fast or Slow response time and “A” or “C” frequency weighting to suit different applications.
curve simulates the response of the human ear, and is therefore the better choice for measuring the sound level of an environment for the purpose of regulatory compliance, workplace design or noise-pollution control. By comparison, the “C” weighting curve is flatter, and is therefore better for measuring the sound level of a piece of machinery. In the U.S., most OSHA-mandated sound level measurements are made by instruments set for slow response and “A” frequency weighting.
session. While the digital display is showing the minimum sound value, the meter continues to measure real-time sound level inputs and to display its results on the analog bar graph. To display the maximum sound level measured since entering Recording mode, press the REC button briefly one more time. The text MAX will replace MIN on the top line of the display and the digital display will indicate the highest sound volume measured during this recording session.
However, the digital display is updated only when the meter detects a louder sound. To enter MAX HOLD mode, press the MAX HOLD button at the lower right of the front panel. To exit this mode, press the MAX HOLD button again DISABLING AUTO POWER OFF By default, the meter powers off automatically after 20 minutes to avoid discharging the batteries. However, you can disable this feature if you would like to track sound levels over a longer period of time.
CALIBRATING THE METER The DSM8925 must be calibrated before it can make accurate sound level measurements. To begin, obtain a standard acoustic calibrator with a 94 dB output, such as General Tools & Instruments’ SCAL1356. Then enter Manual Ranging mode and choose the 80 to 110 dB range using the steps outlined on p. 9. Changing the response time is unnecessary. However, make sure that “C” weighting is chosen and that that the meter is not operating in MAX HOLD mode.
SPECIFICATIONS Measurement Range Measurement Accuracy Digital Display Resolution Digital Display Refresh Period Analog Bar Graph Resolution Analog Bar Graph Refresh Period Frequency Range Display Window Size Digit Height Microphone Diameter/Type Battery Life Analog Output Operating Temperature Storage Temperature Dimensions Weight Power Source 16 40 to 130 dB over four ranges ±2 dB 0.1 dB 160 milliseconds 1 dB 40 milliseconds 31.5 Hz to 8 kHz 1.18 (W) x 1.38 (H) in. (30 x 35mm) 0.6 in. (15.2mm) 0.5 in.
MAINTENANCE TIPS When the icon appears at the upper right of the display, it’s time to replace the four AAA batteries that power the instrument (although measurements will remain valid for several hours after the icon first appears). To replace the batteries, follow the Setup Instructions on p. 8. Remove the batteries when storing the meter for an extended period of time. Do not drop or disassemble the meter or immerse it in water.
Acceptance of the exclusive repair and replacement remedies described herein is a condition of the contract for purchase of this product. In no event shall General be liable for any incidental, special, consequential or punitive damages, or for any cost, attorneys’ fees, expenses, or losses alleged to be a consequence of damage due to failure of, or defect in any product including, but not limited to, any claims for loss of profits.
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GENERAL TOOLS & INSTRUMENTS 80 White Street New York, NY 10013-3567 PHONE (212) 431-6100 FAX (212) 431-6499 TOLL FREE (800) 697-8665 e-mail: sales@generaltools.com www.generaltools.com DSM8925 User’s Manual Specifications subject to change without notice ©2011 GENERAL TOOLS & INSTRUMENTS NOTICE - WE ARE NOT RESPONSIBLE FOR TYPOGRAPHICAL ERRORS.
