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PDF OCR Transcript: USER MANUAL Sound Level Meter Model- SLM-04 Webel Mediatronics Limited P-1 Taratala Road, Kolkata – 700088 Ph: (033) 2401 7699 / 5602 Website: webelmediatronics.in Mail to: webelmedia@gmail.com 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 A weighting : Human ear listening response C weighting : Flat response 7 Frequency 20Hz to 20KHz 8 Microphone Electronic Condenser Microphone with -34 dB Sensitivity 9 Time weighting: (Fast & Slow) Fast (t = 200ms) and Slow (t = 500ms) 10 Calibration Easy instrument (e.g., screw driver) with externally fitted calibrator 11 GPS / GSM Onboard GSM Module to have Location, Date & Time 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 Data can be recorded for a duration of 1⁄2 an hour. Data can be uploaded to a host computer through built in USB interface. 13 Printer Onboard miniature thermal printer for taking print out of the measurement data along with the Location, Date and Time information. Instant Printing through dedicated key switch. Thermal paper roll width : 2” 14 Operating condition 0 to 45°C temperature and 90% relative humidity (non- condensing) 15 Power supply Built in 7.4V Rechargeable Battery Pack. 16 Others Carrying case + Battery Charger 17 Weight 675 grams (approx)
  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 on the top which provides paper feed option which can be used when the printer is not in printing mode. GPS Module: This module helps in acquisition of GPS information like date, time, latitude and longitude. After power-up GPS module takes around 4-5 seconds for initialization. Thereafter the information gets updated at every second. For getting correct reading of data one has to stand under the open sky. USB: The USB port is located at the right side of the instrument. This can be used to upload data stored in the flash memory to PC / laptop. An USB-UART bridge driver from Cypress “CypressDriverInstaller_1.exe“ is to be installed in the PC / laptop to upload stored data from the device. The driver may be downloaded from the Cypress website or may be obtained from WML. Power Supply: A 7.4 Volt, 5200mAh Li-ion rechargeable battery is the main source of power for this instrument. The instrument will fail to latch in power-on mode if the battery is sufficiently discharged. In this condition battery needs to be charged for 3 hours only with the charger supplied. A charger socket has been provided at the left side plane of the instrument for connecting charger. Calibration Potentiometer: One trimmer is kept at the top left of the instrument for calibration of the instrument by a fine screw driver. Firmware: The firmware has been designed to have a convenient mode of operation through an access control of a main menu and submenu items. The components of main menu are explained below. a. SAM – This is a short form of “Sampling”. This menu enables user to select between 200ms (Fast) and 500ms (Slow) time weighting. b. FRQ – This is a short representation of “Frequency” weighting. This menu provides user to select between “A” and “C” frequency weighting. c. RAN – This is a short form of “Range”. This menu provides user to choose between two probable options : “Low” (40-90dB) and “High” (80-130dB). d. LEQ – This enables user to choose between dB and Leq options. A “0” indicates the menu mode is dB and any non-zero value indicates Leq time in minutes. The possible values are between 1-30. The display indicates dB / Leq value as per this setting. e. REC - This is an abbreviation form of “Recording”. This menu enables user to take print- out (PRN), recording of dataset into flash (SAV), uploading of stored data through USB port (UPL) or erasing the entire flash memory (ERA). Record menu contains four submenus such as under i. UPL – The data stored in flash memory will be uploaded from its zero location upto the last recorded address through the USB port to the PC/laptop. The maximum size of the flash is 0x200000 bytes. One data string comprises of data in the sequence of date, time, latitude, longitude and dB level. Any recording event starts with “$$” and each record is separated from the next one with the “##” string. User has to follow the setting to upload data using any standard Windows based serial communication application like “HyperTerminal”, “Tera Term” etc. Baud rate 115200 Data 8 Stop bit 1 Parity None Flow control None ii. ERA – The entire flash memory can be erased by this selection. iii. SAV – The dataset will start getting stored in seconds in the flash memory if Save is selected once. One more hitting of “Select” switch terminates the recording session. iv. PRN – The current data comprising of date, time, latitude, longitude and dB level, which is being displayed will be printed by thermal printer if this submenu is selected. All the above submenu items will come into action only if the “Select” switch is pressed. Keyboard Display I/O SPI UART UART Printer Controller A/D SPI UART Flash USB Analog Section MIC Functional Block Diagram of SLM-04 GPS Module
  3. Key Function Switches o On/Off Switch: A Tact switch is there at the bottom leftmost side of the front panel of the instrument for device On/Off. Alternate pressing & releasing of the switch makes the system On & Off respectively. o Menu Switch: The switch is provided at the bottom of the front panel to find different options under the highlighted menu such as SAM, FRQ, RAN, LEQ and REC. If you keep on pressing this switch all the submenus under the selected menu will appear one after another. o Left Arrow («) Switch: The switch is available at the bottom of the front panel to move the cursor towards left of the menu bar. When the cursor goes over a menu, the last submenu is displayed (reverse video) on the screen. o Right Arrow (») Switch: The switch is available at the bottom of the front panel to move the cursor towards right of the menu bar. When the cursor goes over a menu, the last submenu is displayed (reverse video) on the screen. o Select Switch : The highlighted setting (reverse video) is enabled by this switch. This is located at the rightmost of the front panel bottom. This switch finally brings the selected option into action.
  4. Device Operation Press On/Off switch once for power on. Pressing the same switch once again will make the device off. However, switching Off action will not happen for 4-5 seconds after power up. The device can be switched off only after splash screen “SLM-04” disappears and main window is displayed. Once the device is ready for operation, a menu bar along with measurement data is displayed at the top of the LCD screen. Go to a particular menu with the help of “Left Arrow” and “Right Arrow” switches. Now, keep on pressing “Menu” switch till the desired submenu is reached. After the desired submenu has arrived, press the “Select” button finally for the selection to be activated. A message corresponding to the selection is displayed at the top line of the display, in place of menu bar, confirms the selection. Press any switch to get back the menu bar once again.
  5. Calibration procedure Please follow the given steps for calibration : 1. Switch on the unit 2. Set Range selection in H mode i.e. 80dB – 130 dB range
  6. Set A / C weighting selection in A-weighting 4. Keep the instrument either in Slow or Fast mode 5. Insert the instrument tip into the calibrator slot & select 94dB 1KC tone in the calibrator 6. Adjust the calibration pot accessible through a small hole positioned at the left side of canopy section of the instrument, so that instrument reads (94±0.5)dB 7. Now remove the calibrator The calibration may be verified for 114dB level also (option available in calibrator). Caution The instrument contains 7.4V, 5200mAh Li-ion battery pack inside. Please be careful to note the following : ➢ Do not tamper or modify ➢ Do not drop the instrument from a height ➢ Do not make direct short between charger terminals ➢ Always use the same charger for charging the battery which is supplied along with the instrument