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:!
!
!
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:!
!
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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BT80i!Sound!Sensor!User’s!Guide! |!3!
Suggested!experiments!!
The!Sound!sensor!can!be!used!in!a!variety!of!experiments!with!sound!waves!such!as:!!
• measure!sound!waveforms!(sound!frequency!and!amplitude),!
• demonstrate!beat!patterns,!
• compare!waveforms!from!various!musical!instruments,!
• measure!the!speed!of!sound!through!air!and!other!materials,!
• display!the!frequency!spectrum!e.g.!Fourier!transform!of!a!sound!signal.!
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4!|!BT80i!Sound!Sensor!User’s!Guide!!
Technical!Specifications!
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Sensor'kind'
Analog,!generates!an!output!voltage!!
between!-10 .. 10 V
Note:!When!no!sound!is!detected!the!output!is!0!V.!
Measurement'ranges'
Air'pressure''
Sound'level''
-45 .. 45 Pa (0.45 mbar )
50 .. 110 dB
Resolution'using''
12'bit'AD'converter'
22!mPa!(0.22!µbar)!
!
Frequency'range!
50!Hz!-!12000!Hz!
Calibration'function'
p!(Pa)!=!4.5!*!V
out
!(V)!
Current!requirement'
<!5!mA!
Connection!
IEEE1394!connector!for!BT-IEEE1394!sensor!cable.!!
Sensor!cable!not!delivered!with!the!sensor.!!
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Warranty:!!
The! Sound! sensor! BT80i! is! warranted! to! be! free! from! defects! in! materials! and!
workmanship!for!a!period!of! 24!months!from!the!date!of!purchase!provided! th at!it!has!
been! used! under! normal! laboratory! conditions.! This! warranty! does! not! apply! if! the!
sensor!has!been!damaged!by!accident!or!misuse.!!
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Note:!This'product'is'to'be'used'for'educational'purposes'only.'It'is'not'appropriate'for'
industrial,'medical,'research,'or'commercial'applications.'' ' ' ' '
Rev. 05/03/2018
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