CMA Dishmachines SOUND SENSOR BT80i User Manual

SOUND%SENSOR!!

BT80i!

USER’S!GUIDE!

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CENTRE FOR MICROCOMPUTER APPLICATIONS

http://www.cma-science.nl

2!|!BT80i!Sound!Sensor!User’s!Guide!!

Short!description!

The! Sound! Sensor! BT80i! is! a! microphone! followed! by! an! internal! amplifier.! This!
microphone! is! mounted! at! one! end! of! the! box.! The! sensor! measures! variations! in! air!
pressure! caused! by! a! sound! wave.! Because! of! the! high! sensitivity,! the! sensor! is! very!
much!suited!to! detect!short!pressure! pulses.! This!offers!the! possibility!to!measure! the!
speed!of!sound.!

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The! sound! sources! that! can! be! used! with! the! microphone! are! tuning! forks,! electronic!
keyboards,! and ! musical! instruments.! You! may! also! investigate! a! human! voice! or! a!
whistle.! When! you! use! the! sound! sensor! make! sure! the! sound! level! is! in! the! correct!
range!to!produce!good!wave!patterns.!If!the!sound!is! to o!loud,!the!wave!pattern!will!be!
“clipped!off”! at! the!top! or! bottom.!In! such! a! case!move! the! microphone!further! from!
the!sound!source,!or!turn!down!the!volume!of!the!sound.!

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By! default! the! sensor! measure! air! pressure! in! the! range! between! -45! ..! 45! Pa.!
Additionally,! by! using! the! calibration! provided! in! the! Coach! software! the! sensor! can!
measure!Sound!Level!in!dB,!in!the!range!between!50!..!110!dB.!

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The! Sound! sensor! can! be! directly! connected! to! the! analog! BT! inputs! of! the! CMA!
interfaces.!The!sensor!cable!BT!-!IEEE1394!needed!to!connect!the!sensor!to!an!interface!
is! not! supplied! with! the! sensor! and! has! to! be! purchased! separately! (CMA! Article!
BTsc_1).!!

Sensor!recognition!

The! Sound! sensor! BT80i! has! a! memory! chip! (EEPROM)! with! information! about! th e!
sensor:! its! name,! measured! quantity,! unit! and! calibration.! Through! a! simple! protocol!
this! information! is! read! by! the! CMA! interfaces! and! the! sensor! is! automatically!
recognized! when! it! i s! connected! to! these! interfaces.! ! If! your! Sound! sensor! is! not!
automatically! detected! by! an! interface! you! have! to! manually! set! up! your! sensor! by!
selecting!it!from!the!Coach!Sensor!Library.!!

Calibration!!

The!CMA! Sound!sensor! BT80i!is! supplied! calibrated.!The! output! of! the! sensor!is! linear!
with!respect!to!the!measured!air!pressure:!

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p(Pa)!=!4.5!*!V

out

!(V).!!

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Additionally! Coach! offers! the! sensor! calibration! in! dB.!This! calibration! is! based! on! the!
procedure! of! determining! the! average! sound! pressure! p! (root! mean! square! average)!
and!calculating!the!sound!pressure!level!in!decibels!from:!

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Lp=20!log!(p/p0)!where!p0=!2.5x!10-5!Pa.!

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The! Coach! software! allows! selecting! the! calibration! supplied! by! the! sensor! memory!
(EEPROM)!or!one!of!calibrations!stored!in!the!Coach!Sensor!Library.!For!better!accuracy!
the!pre-defined!calibration!can!be!shifted.!!

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