Webel Mediatronics SLM-04 User Manual

USER MANUAL

Sound Level Meter

Model- SLM-04

Webel Mediatronics Limited

P-1 Taratala Road, Kolkata – 700088

Ph: [phone] / 5602

Website: webelmediatronics.in

Mail to: [e-mail]

Introduction

Sound Level Meter (SLM-04) is designed according to the specification outlined by West Bengal
Pollution Control Board. This is a type-2 sound level measuring instrument useful for
measurement of sound / noise level at public place, factories, workspace etc.

It is a battery operated handheld instrument having a suitable carrying case. The instrument
provides 500ms and 200ms time weighted reading of sound level which is selectable through
front panel switches. Leq measurement can be done for a fixed time interval of 1-30 minutes,
with one minute resolution. A Graphic LCD display shows the readings. Active filters are used
for implementation of A & C weighting frequency characterization. Two selectable
measurement ranges are available: Low (40dB - 90dB) and High (80dB - 130dB).

1. Specification of Sound Level Meter Model No : SLM-04

Sl. No. Item Specification

1 Display LCD Graphic Display
2 Measurement a) NOISE LEVEL

dB (A & C frequency weighting)
Time weighting (Fast = 200ms / Slow = 500ms) Output in dB

b) LEVEL EQUIVALENT (Leq)
Energy-averaged noise level, over programmable time
duration with 1minute resolution,
Maximum upto 30 Min.

3 Measurement range 40 to 130 dB (only input) in two slots

Low : 40 – 90 dB

High : 80 – 130 dB
4 Resolution 0.1 dB
5 Accuracy (23 ± 5⁰C) Calibrating at 94dB with IEC 651 type 2,

accuracy = ±1.5dB at 1KHz) F.W.
6 Frequency

weighting network
7 Frequency 20Hz to 20KHz
8 Microphone Electronic Condenser Microphone with -34 dB Sensitivity
9 Time weighting:

(Fast & Slow)
10 Calibration Easy instrument (e.g., screw driver) with externally fitted

11 GPS / GSM Onboard GSM Module to have Location, Date & Time

A weighting : Human ear listening response
C weighting : Flat response

Fast (t = 200ms) and Slow (t = 500ms)

calibrator

information of the place of measurement.
Location : in Latitude & Longitude up to second ( “ ) precision
Date : DD:MM:YYYY format

Time: HH:MM:SS format

12 Recording & Data

uploading
13 Printer Onboard miniature thermal printer for taking print out of the

14 Operating condition 0 to 45°C temperature and 90% relative humidity (non-

15 Power supply Built in 7.4V Rechargeable Battery Pack.
16 Others Carrying case + Battery Charger
17 Weight 675 grams (approx)

Data can be recorded for a duration of ½ an hour. Data can be
uploaded to a host computer through built in USB interface.

measurement data along with the Location, Date and Time
information. Instant Printing through dedicated key switch.
Thermal paper roll width : 2”

condensing)

2. Functional Description

Controller Chip: The instrument has been designed around PSoC from Cypress Semiconductor.

This is a versatile state of art mixed signal Processor having configurable components like
multiplexers, ADC, DAC, logic gates etc. The firmware resides in the 64KB flash memory within
the chip. It implements analog data acquisition, mathematical computations as well as handles
display & keyboard functions as a central processing unit for the instrument.

The design implements an external SPI flash memory of 2MByte size for recording of data.

Analog Processing Section: The condenser microphone sensitivity is typically -34dB. Suitable
gain adjustment is done at Mic pre-amplifier circuit. Bipolar instrumentation amplifiers from
Analog Devices are used for implementation of A-weighting and C-weighting frequency
characterization.

LCD Display: A 4x22 character graphic LCD display shows the measured level of sound / noise in
dB with 0.1dB resolution along with GPS information. At the top line of the display a menu is
displayed for selecting various options under different categories. The display provides suitable
means for selection of different options available under each menu. It consumes a maximum of
60mA current at 3.3V.

Printer: A miniature thermal printer is housed in the instrument to take the print-out of the last
updated dB level along with date, time, latitude and longitude information. The printer
consumes a peak current of 1.5A at startup. This has got a separate regulated power supply
section and has an UART interface with the controller. The printer gets ready for printing
instantly after the instrument gets ready on power up. There is a red LED located on printer
panel, which keeps flashing if there is no paper in the printer. This also carries a built-in switch