Tugas Elins Journal-CONVERT2

8/12/2019 Tugas Elins Journal-CONVERT2

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Sensors and Actuators A 202 (2013) 147154

Contents lists available at ScienceDirect

Sensors and Actuators A: P!sical

" o u r n a l o # e $ a % e : & & & ' e l s e v i e r ' c o # l o c a t e s n a

ulti*sensor s!ste# &it +luetoot connectivit! ,or non*invasive

#easure#ents o, u#an bod! $!sical $ara#eters

A' De$ari- A' .la##ini- S' /inaldi- A' eoli

De$art#ent o, n,or#ation n%ineerin%- niversit! o, +rescia- ia +rane 3- 25123 +rescia- tal!

a r t i c l e i n , o

Article istor!:

/eceived 27 6ctober 2012

/eceived in revised ,or# 30A$ril 2013 Acce$ted 1 a!

2013

Available online 1 a! 2013

e!&ords:

Poto$let!s#o%ra$ic

sensor 8issue

i#$edance

#easure#ent 9ireless

sensor

Portable s#art

sensor on*

invasive

#easure#ent

a b s t r a c t

n te last ,e& !ears- te availabilit! o, $o&er,ul $ersonal co#$utin% devices- li;e

s#art$ones- as o$ened ne& scenarios to te so called $eri#ental caracteriation o, te $rotot!$e- $er,or#ed b!

usin% a s$eci,icall! desi%ned a$$lication ,or Android s#art$one s!ste#s- as

de#onstrated te validit! o, te $ro$osed a$$roac'

B 2013 lsevier +'' All ri%ts reserved'

1. Introduction

onitorin% $!sical data- $articularl! durin% s$ort

activities- can $rovide atletes &it use,ul in,or#ationabout te bod! res$onse to ,ati%ue' , te in,or#ation

&as %iven in real*ti#e- te atlete could i##ediatel!

reco%nie $otential serious aards ,or is ealt- ,or

e>a#$le due to overstrain- tus reducin% or inter*ru$tin%

te activit!' oreover- trainin% $ro%ra#s tailored to te

atlete caracteristics #a! ta;e advanta%e o, te real*

ti#e in,or*#ation- b! su%%estin% i# o& to ad"ust te

activit! in order to i#$rove is $er,or#ance' A s!ste#

able to ac@uire suc data ,ro# te u#an bod! #ust be

co#$act- li%t and $ortable- non*invasive and lo&*$o&er-

in order to be batter!*o$erated durin% outdoor use'

Several devices are toda! available on te #ar;et ,or

suc $ur*$oses ,or instance eart rate belts are used to

collect in,or#ation

; Corres$ondin% autor' 8el': 3 0303715 ,a>:3 03030014' *#ail address:alessandro'de$ariEin%'unibs'it (A' De$ari)'

024*4247F see ,ront #atter B 2013 lsevier +'' All

ri%ts reserved'

tt$:d>'doi'or%10'101G"'sna'2013'05'001
http://www.sciencedirect.com/science/journal/09244247mailto:[email protected]:[email protected]:[email protected]:[email protected]://var/www/apps/conversion/tmp/scratch_2/C:%5C%5CUsers%5C%5CSAMSUNG%5C%5CDownloads%5C%5Cdx.doi.org%5C%5C10.1016%5C%5Cj.sna.2013.05.001http://var/www/apps/conversion/tmp/scratch_2/C:%5C%5CUsers%5C%5CSAMSUNG%5C%5CDownloads%5C%5Cdx.doi.org%5C%5C10.1016%5C%5Cj.sna.2013.05.001mailto:[email protected]:[email protected]://var/www/apps/conversion/tmp/scratch_2/C:%5C%5CUsers%5C%5CSAMSUNG%5C%5CDownloads%5C%5Cdx.doi.org%5C%5C10.1016%5C%5Cj.sna.2013.05.001http://var/www/apps/conversion/tmp/scratch_2/C:%5C%5CUsers%5C%5CSAMSUNG%5C%5CDownloads%5C%5Cdx.doi.org%5C%5C10.1016%5C%5Cj.sna.2013.05.001http://www.sciencedirect.com/science/journal/09244247


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,ro# atlete bod! and to trans#it data to s#art$ones or

dedi*cated devices' ?o&ever- suc s!ste#s are usuall!

rater invasive and re@uire a care,ul $ositionin% o, te

sensitive ele#ents- in order to $rovide #eanin%,ul

results' n addition- te connection o, tese sensin%

devices to a s#art$one ,or data visualiation re@uires

te use o, e>ternal don%le- since t!$icall! teir

co##unication $ro*tocol is not nativel! su$$orted' n H1I-

a ne& a$$roac as been $ro$osed to i#$rove teco#,ort and te @ualit! o, te $rovided eart rate

#easure#ents' 8e sensor is $laced on te user earlobe

and te ac@uired data are trans#itted &it &ireless

tecnolo%! to an end*device ,or data $rocessin% and

visualiation' 8ere,ore- te co#$le>it! and te cost o,

te sensor a$$aratus can be #aintained lo&- &ereas

te $o&er consu#$tion is co#$arable to te one o, te

&ireless trans#ission unit' 8e $ur$ose o, te $resent

is to i#$rove te s!ste# in H1I- in order to collect

additional $!s*ical in,or#ation ,ro# te atleteJs bod! in

$articular- beside te $oto$let!s#o%ra$ic (PPK)

sensor o, H1I- te #easure#ent o, te earlobe tissue

i#$edance as been considered H2I' Data ,ro# botsensors are trans#itted b! te sa#e audio +luetoot

inter,ace-


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14 A' De$ari et al' Sensors and Actuators A 202 (2013) 147154

&itout te need ,or additional $rocessin% unit'

8e ai# is to use te audio si%nal to code-

tan;s to si#$le %lue lo%ic- t&o biolo%ical

si%nals' Since data collected ,ro# te sensors

ave not $articularl! $rivac! issues- codin%

and $rotection o, trans#itted data (li;e ,or

instance in H3I) ave not been considered'

8e PPK sensor is used to #onitor

#odi,ications in blood vol*u#e in te arteries-#easurin% te variation o, te li%t trou% te

tissues H4I' 8e ,re@uenc! o, te si%nal

$rovided b! te sen*sor is used to esti#ate

te eart beat rate and to %ater additional

in,or#ation ,ro# te caracteristics o, te

cardiac si%nal' .or e>a#*$le- b! anal!in% te

eart beat variabilit! H5-GI- it is $ossible to

detect events tat can seriousl! in"ure

atletes- suc as arr!t*#ias or arterial

stenosis and occlusions' 8e use o, a second

sensor- o$eratin% &it a di,,erent &avelen%t

or- si#ilarl!- a sin%le sen*sor e#$lo!in% t&o

di,,erent &avelen%ts- &ould #a;e $ossible

te esti#ation o, te o>!%en saturation inblood as &ell H7-I' 6n te oter andte bio*

i#$edance #easure#ent is &ell*;no&n in lit*

erature HIto #onitor te can%es o, biolo%ical

tissue $ro$erties- li;e ,or e>a#$le ions

concentration due to $!sical e,,ort' 8e #on*

itorin% o, suc $ro$erties #a! el$ te atlete

to understand te bod! res$onse to te

current activit! and- in accordance- to ad"ust

is $!sical e,,ort' n te $resent - te

#easure#ent o, te earlobe tissue i#$edance

is acieved b! enca$sulatin% t&o elec*trodes

in te cli$ su$$ort o, te PPK sensor' +! doin%

tis- te sie and &ei%t o, te sensor unit

a$$lied on te atlete earlobe are not

substantiall! increased'

Data trans#ission ta;es advanta%e o, te

&ell*;no&n and &ides$read +luetoot &ireless

tecnolo%!- &ic is alread! used in several

a$$lications ,or collectin% sensor data H10-11I'

n ,act- +luetoot is nativel! available in al#ost

all $ortable devices- suc as s#art$ones and

tablets- &ic- in addition- are te best can*

didates ,or te data elaboration and

visualiation- tan;s to te $resence o,

relativel! i% co#$utational resources and o,

a touc screen ,or te user interaction' 6ter

co##unication tecnolo%ies t!$icall! ado$ted

to collect data ,ro# sensors- li;e 9i*.i H12Iand 02'15'4 H13I- $resent li#itations

re%ardin% te $o&er con*su#$tions (9i*.i)

and te su$$ort b! s#art$ones (

02'15'4)' 6ter interestin% a$$roaces- li;e

te one $ro$osed in H14I- are not suitable ,or

te $ro$osed a$$lication- since te sensors

are con*nected e>ternall! to te earlobe'

Latel!- +luetoot as been ado$ted ,or

data trans#ission also in sensor s!ste#s ,or

s$ort activities- tus #a;in% $ossible a direct

co##unication lin; &it te user s#art$one'

?o&ever- co#$at*ibilit! issues arise ,ro# tis

a$$roac in ,act- +luetoot standard de,ines a

broad set o, co##unication $ro,iles- oriented,or data as &ell as audio (strea#in%)

trans#ission- di,,erentl! su$$orted b! te #ost

&ides$read devices on te #ar;et (Android-

i6S- 9in*do&s Pone ter#inals)' Currentl!-

te onl! $ro,ile i#$le#ented b! all te devices

is te ?ands*.ree Pro,ile (?.P)- #ainl! used

,or co#*#unication &it co##ercial eadsets'

8e ?.P solution as been cosen ,or data

co##unication- to assure te ,ull co#$atibilit!

o, te $ro$osed sensor s!ste#s &it te #ost

available end*devices' 8is led to te need o,i#$le#entin% an e,,ective ,irst conditionin%

electronics ,or sensor data- &ic &ill be

dee$l! described in te ,ollo&in%'

.or de#onstrative $ur$oses- a data

ac@uisition and user inter*,ace $ro%ra##e as

been i#$le#ented in Android environ#ent'

?o&ever- bein% te $ro$osed solution

inde$endent o, te used end*device- te

develo$#ent o, a$$lications ,or oter ter#inals

e@ui$$ed &it di,,erent o$eratin% s!ste#s is

,acilitated H1I'

2. The proposed system

8e $ro$osed s!ste# is co#$osed o, tree

units- as illustrated in .i%' 1' 8e Sensor unit

includes te sensors a$$lied on te user


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Fig. 1. +loc; sce#e o, te overall s!ste# te circled

$art is te $ro$osed solution ,or data #easure#ent and

trans#ission'

earlobe ,or te $!sical data #easure#ent'

8e analo% ,ront*end $rovides $ro$er sensor

e>citation si%nals and i#$le#ents te ,irst

conditionin% electronics o, sensor data'

oreover- as detailed in te ,ollo&in%- it,urnises data to trans#it to te 8rans#ission

unit in a suitable ,or#at' 8e latter is devoted

to te +luetoot trans#ission o, data to s$eed

u$ te desi%n $rocess- a co##ercial

+luetoot ear$one- able to trans#it audio

data- as been used ,or tis $ur*$ose' 8e

batter! o, te ear$one is used to $o&er also

te oter t&o units o, te s!ste#'

8rans#itted data can be ac@uired b! an!

device &it +luetoot ca$abilities' n order to

de#onstrate te validit! o, te $ro$osed

sensor s!ste#- a s#art$one e@ui$$ed &it

Android as been used as te end*device' A

suitable so,t&are (A$$) as been develo$ed toso& te ac@uired data and to save te# as

an audio ,ile ,or ,ur*ter o,,*line anal!sis' n te

,ollo&in%- te tree units o, te sensor s!ste#

&ill be detailed- &ereas te s#art$one A$$

descri$tion &ill be included in Section 3'

2'1' Sensor unit

8e sensor unit consists o, an o$tical PPK

sensor and t&o elec*trodes ,or te i#$edance

#easure#ent' 8e utilied PPK sensor ado$ts

te trans#issive tecni@ue and tus it is

co#$osed o, a $ototransistor and a

$otodiode to be $laced ,ace*to*,ace- &it te

tar%et tissue in te #iddle' 8e $otodiodee#its an in,rared bea# &ic is detected b!

te $ototransistor once te li%t as crossed

te tar%et tissue' An increase o, blood volu#e

in te tissue deter#ines a decrease o, te li%t

received b! te $ototransistor tere,ore- an

electric si%nal ,ollo&in% te beaviour o, te

blood volu#e can be ac@uired' Several details

can be obtained b! usin% te

$oto$let!s#o%ra$ic &ave,or#' A sin%le

$eriod is co#$osed o, t&o $ea;s se$arated b!

a s#all di$- called Dicrotic otc it re$resents

te closure o, te aorta &it te end o, s!stole-

,ol*lo&ed b! te be%innin% o, te diastole' 8e

co#$lete cardiac c!cle can be used ,or te

eart beat rate esti#ation' oreover- recent

s H5-GI illustrate tat is $ossible to

evaluate te occurrence o, arr!t#ias or

arterial stenosis and occlusions ,ro# te eart

rate variabilit!' 8e t&o sensor co#$onents o,

te PPK- tat is te $ototransistor or

$otodiode- ave been $laced in te #iddle o,

t&o co$$er rin%s actin% as electrodes ,or te

i#$edance #easure*#ent' ac electrode as

te ,or# o, a circular rin% &it 1 ## tic;ness'

8e dia#eters o, te outer and inner

circu#,erences o, te rin%s are 10 ## and 5

##- res$ectivel!' lectrical connections o, te

PPK sensor are assured b! #eans o, suitable

ollo&s in te #etallic rin%s' 8e attraction,orce o, t&o #a%nets as been used to ;ee$

te rin%s in contact &it te t&o sides o, te

earlobe and to


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A' De$ari et al' Sensors and Actuators A202 (2013) 147154

Vcc

RD RC

PPG

(a)

RST

Ct

(Ctot) CSTFig. 2. 8e i#$le#ented $rotot!$e o, te Sensor unit'

(b)%uarantee a %ood ali%n#ent bet&een te t&o sensor co#$onents' Fig. 4. (a) 8e $olariation and ,irst conditionin% electronics ,or te PPK sensor' (b)8&o c!lindrical #a%nets &it circu#,erence e@ual to te electrode 8e i#$edance #easure#ent and #odulation circuits'outer one and tic;ness o, 2 ## ave been %lued to te rear o,

eac electrode te #a%net $ole orientation as been suitabl! co* analo% ,ront*end' 8e PPK sensor- as illustrated be,ore- is co#$osedsen to #a;e te rin%s attractin% eac oters &en te t&o PPKo, a $otodiode and a $ototransistor a si#$le $olariation circuitco#$onents are ,ace*to*,ace' A $icture o, te realied sensor unitis realied b! #eans o, te t&o resistors /Dand /C- as in .i%' 4(a)'$rotot!$e is so&n in .i%' 2' Co#$ared to te solution ado$ted

in H1I- &ere a cli$ as been used to sustain te PPK- te #a%* 8e eart beat &ave,or# C ,ro# te o$tical sensor as ver! lo&

net a$$roac #a;es te ali%n#ent o, te PPK sensor co#$onents a#$litude and it is rater nois!' 8e #a>i#u# a#$litude o, Cis

sli%tl! #ore critical neverteless- it %uarantees a #ore e,,ective on te order o, ,e& #illivolts and it as a DC o,,set' A ,ilterin% sta%e-

co#$osed o, a ,irst order i%*$ass ,ilter (/?P and C?P) is used toelectrode contact &it te tissue' asiness o, a$$lication on te

tar%et (e'%'- earlobe) and re#oval are o&ever assured' re#ove te DC o,,set- &ereas an a#$li,!in% sta%e- co#$osed o,

an active ,irst order lo&*$ass ,ilter (6A- /LP1- /LP1- and CLP- cut ,re*t sould be noticed tat te electrodes are in direct contact &it

te s;in and tere,ore an electric current can ,lo& trou% te tis* @uenc! o, about 5 ?)- as been used to $re$rocess C- obtainin%

sue' ?o&ever- bein% te s!ste# lo&*volta%e and batter!*o$erated- te PPKsi%nal'

tis does not re$resent a ris; ,or te u#an tar%et' .or i#$roved 8e circuit dedicated to te tissue i#$edance esti#ation- b!#eans o, te i#$le#ented electrodes- ta;es advanta%e o, te ,actsa,et!- te electrodes can be covered &it an insulatin% ,il#: t&otat te earlobe i#$edance can be a$$ro>i#ated as a $ure ca$ac*ca$acitive co#$onents 2Ci- due to te insulator- are introduced initive co#$onent- &en te o$eratin% ,re@uenc! is over a certainseries to te tissue i#$edance Mt- as so&n in .i%' 3' 8e overallvalue (about 20 ;?)' 8is consideration &ill be better detailede,,ect is a ca$acitive co#$onent Ciin series &it Mt- &ic #a;esin Section 3' 8ere,ore- te #easure#ent o, Mt (or Mtot- in case o,

te #easured i#$edance Mtotto be as described in (1)' insulatin% ,il#) #erel! beco#es te esti#ation o, te ca$acitive1 1

N /e(Mt) " #(Mt) O (1)co#$onent Ct(Ctot)- tus a si#$le ,irst conditionin% electronics can

MtotN Mt "2_,C 2_,C

i i be i#$le#ented' As stated be,ore- a co##ercial +luetoot device

Also in te case &en te insulator ,il# is a$$lied- te in,or#a* able to trans#it an audio si%nal &ill be used' .or tat reason- a

sin%le si%nal in te voice band&idt carr!in% bot te in,or#a*tion about te tissue i#$edance Mt can be neverteless obtainedtion related to te PPK and i#$edance sensor need to be $rovided

,ro# te esti#ation o, Mtotand te ;no&led%e o, Ci' to te 8rans#ission unit' n H1I- a si#$le #etod based on si%nal

2'2' Analo% ,ront*end#odulation &it a constant*,re@uenc! and s@uare &ave,or# car*rier as been used to si,t te PPK si%nal in te audio band&idt-

8e sensors need to be $ro$erl! e>cited and sensor out$ut si%* tus #a;in% it suitable ,or trans#ission &it te ado$ted +lue*

toot device' n tis - a si#ilar a$$roac as been ,ollo&ednals ave to be suitabl! conditioned be,ore trans#ission tesein ,actin,or#ation about te tissue ca$acitance as been coded in

tas;s are $er,or#ed b! te electronic circuits i#$le#ented in te te #odulatin% carrier ,re@uenc!' n tis &a!- a sort o, co#bina*

tion bet&een a $ulse*,re@uenc! #odulation and $ulse*a#$litude

#odulation is obtained and in,or#ation related to bot sensors is

co#bined to create a sin%le audio si%nal'

An oscillator circuit based on a Sc#idt 8ri%%er lo%ic %ate is

used to %enerate te tissue*ca$acitance*de$endent s@uare &ave*

,or# S8- as so&n in .i%' 4(b)' 8e oscillator o$erates at a ,re@uenc!

%reater tan 20 ;?- in order to consider valid te a,ore#entioned

a$$ro>i#ation o, tar%et i#$edance as a $ure ca$acitive co#$o*

nent tis ,re@uenc! value is o&ever out o, te use,ul audio

band&idt' 8us- S8 is not a$$ro$riate to be directl! used as te

#odulation carrier- but it needs to be $rocessed b! a Prescaler- to

Fig. 3. 8e e@uivalent #odel o, te i#$edance sensor &en te electrodes are reduce te ,re@uenc! into te audio band' ventuall!- te PPK si%nal


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covered &it insulatin% ,il#s' #odulation is $er,or#ed b! #eans o, a co$$er circuit- consistin%


7/14


o, te 6S transistor controlled b! te

s@uare &ave,or# Car ' /esu#in%- te

obtained sin%le si%nal +8 - &ic is in te

audio band and tus can be directl! ac@uiredb! te 8rans#ission unit- carries tein,or#ation about te PPK sensor in tea#$litude and data related to te tar%etca$acitance in te ,re@uenc!'

2'3' 8rans#ission unit

odern $ersonal devices- li;e

s#art$ones and tablets- are usu*all!

e@ui$$ed &it di,,erent co##unication

inter,aces- ,or instance S+- 9i*.i- and

+luetoot' n co#$arison &it oter

tecnolo%ies- +luetoot as several

advanta%es- suc as si#$le co##unication

stac;- sa,e co##unication cannel- and

availabilit! o, lo&*cost and lo&*$o&er devices

H1I' .or tese reasons- +luetoot is t!$*icall!

e#$lo!ed to $rovide co##unication &it add*

on devices- li;e ear$ones- eadsets- %a#edevices and #an! #ore' Latel!- a ne& release

o, +luetoot standard is available- te so

called +lue*toot Lo& ner%! (+L) H15I-

&ic is also ;no&n &it te na#e +luetoot

S#art' 8!$icall! tis $rotocol is ado$ted ,or te

devel*o$#ent o, sensors net H1GI- &ere

te $o&er consu#$tion is one o, te #ain

desi%n $ara#eters- li;e in #edical and ,itness

a$$liances H17I' everteless- des$ite its lo&

$o&er consu#$tion- co#$arable to oter ver!

lo& $o&er tecnolo%! li;e 02'15'a H1I-

tis solution cannot be e#$lo!ed in te

$ro$osed a$$roac- since a $ro,ile ,or te

continuous trans#ission o, data strea# is notavailable' n addition- onl! i%*end devices

are e@ui$$ed &it +L at $resent ti#e- li#itin%

its co#$atibilit!- &ic is one o, te #ain

advanta%es o, te $ro$osed a$$roac'

8ere are several +luetoot $ro,iles

available ,or data as &ell as audio

co##unication o&ever- not all o, te# are

i#$le#ented b! te o$eratin% s!ste#s

ado$ted in s#art$ones and tablets' .or

instance- Android su$$orts so#e o, te

$ro,iles (data and audio) $rovided b! te

standard- &ereas i6S i#$le#ents oter

$ro,iles (?.P 1'5- P+AP- A2DP- A/CP- PA-

?D) not co#$atible &it te $revious ones'

8e audio ?ands*.ree Pro,ile (?.P) as

been selected ,or te trans#ission o, te

sensor si%nal- because it is su$$orted b! te

#ost o, te devices on te #ar;et (included

Android- i6S s!s*te#s and 9indo&s Pone )

and due to te eas! recover! o, te

trans#itted sensor data at a$$lication level'

8e ?ands*.ree Pro,ile de,ines o& a eadset

(


8/14

(a)5'00302

3'7502

Mag 2'5002

1'2502

0'0000

0 4000 000 12000

Frequency !z"

(b) 0

#hase *40

*0

0 4000 000 12000

Frequency !z"

Fig. $. 8e #a%nitude (a) and $ase (b) o, te earlobe

i#$edance Mt #easured &it te $ro$osed sensor

(&itout insulatin% ,il#) and ac@uired &it an i#$edance

anal!ser'

$ase o, te earlobe i#$edance #easured

&it te sensor a$$lied to a $erson in nor#alconditions are so&n' n tis case- te elec*trodes ave been a$$lied &itout teinsulatin% ,il#- tere,ore te %ra$s are related

to te actual tissue i#$edance Mt' t sould benoticed tat &en te ,re@uenc! increases- te

i#$edance $ase decreases to&ards O0Q -

tus indicatin% tat a ca$acitive co#$o*nent Ctis beco#in% #ore and #ore si%ni,icant' , te#easure#ent is $er,or#ed &it a ,re@uenc!%reater tan about 20 ;?- te tis*suei#$edance can be #odelled b! usin% onl! tei#a%inar! $art or- e@uivalentl!- b! utiliin% a

ca$acitive co#$onent Ct- as described in (2)'

MtN /e(Mt) "(#(Mt)) R "(#(Mt)) N O"

1

(2)2_,CtSi#ilarl!- &en te insulatin% ,il# is used

bet&een te tissue and te electrodes- tetotal i#$edance Mtotcan be #odelled b! usin%onl! te i#a%inar! $art- &ic is related to aca$acitive co#*$onent Ctot- de$endin% on Ctand Cias in (3) and (4)'

Mtot R "(#(Mtot)) N " #(Mt) O

1

2_,Ci1 1 1

N O" N O" (3)2_,Ct 2_,Ci 2_,Ctot

1 1 1 (4)

N Ctot Ct Ci

n .i%' G- te ac@uisition o, Mtot$er,or#ed&it te i#$edance anal!ser is so&n' t is&ort notin% tat te beaviour starts to besubstantiall! ca$acitive at o$eratin%,re@uencies lo&er tan in te $revious casetis is due to te $redo#inance o, te

ca$acitive e,,ect Cio, te insulator'n order not to lose sensitivit! in te

#easure#ent o, te tar%et i#$edance- it isi#$ortant to accuratel! select te #aterial ,orte insulator ,il# in $articular- esti#atedvalues &it te realied sen*sor $rotot!$e are

Ci R 10 $. and Ct R 1 $. &it o$eratin%

,re@uenc! o, about 100 ;?'A 8CM8020*PA/ device $roduced b!

isa! se#iconductor as been ado$ted as

te PPK sensor H20I' 8e #ain caracteris*tics

are: 50 n# bea# &avelen%t- G0 #A no#inal

current and


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A' De$ari et al' Sensors and Actuators A202 (2013) 147154 151

(a)1G0000

%&"

120000

Mag 0000

40000

0

0 4000 000 12000 1G000 20000

Frequency !z"

(b) 0

#hase'eg"

*40

*0tot

*120

0 4000 000 12000 1G000 20000

Frequency !z"

Fig. (. 8e #a%nitude (a) and $ase (b) o, te earlobe i#$edance Mtot #easured &it te $ro$osed sensor (&it

insulatin% ,il#) and ac@uired &it an i#$edance anal!ser'

1'25 ,or&ard volta%e o, in,rared led- 250 A current re@uired b! te $ototransistor' A di%ital sco$e

ac@uisition o, te non*,iltered sensor out$ut (Co, .i%' 4(a)) is so&n in .i%' 7 te si%nal is raternois!- even tou% te eart beat is alread! distin*%uisable' A di%ital sco$e ac@uisition o, te

obtained PPK ,iltered si%nal (PPKo, .i%' 4(a)) is so&n in .i%' ' .ro# PPK- in,or#a*tion aboutbeat rate- stee$ness o, s!stole $ase- its a#$litude and $eriod- localiation o, Dicrotic notc andte $resence o, te

diastole $ase can be easil! obtained' A lo&*$o&er o$erational a#$li,ier (8e>as nstru#ents

L35- &it su$$l! current o, about 5 A- at 3'3 ) as been used ,or te active ,ilter i#$le#enta*

tion'

8e oscillation ,re@uenc! o, te Sc#idt 8ri%%er circuit o, .i%' 4(b) as been tuned bet&een 70;? and 100 ;?- to o$erateinside te o$ti#al res$onse band&idt o, te tissue i#$edance' 8ePrescaler as been i#$le#ented b! usin% an *bit di%ital counter- lo&erin% te oscillator out$ut

S8,re@uenc! o, a ,actor o, 25G te ,inal ,re@uenc! value is bet&een about 270 ? and 400 ?- in

accordance &it te re@uired band ,or te audio si%nal to be trans#itted H1I' A detail o, PPKand

#odulated PPK si%nal (+8 o, .i%' 4(b)) is so&n in.i%' ' .or tis sta%e- a 74?C14 Sc#idt

8ri%%er inte%rated circuit and a 74?C33 counter- bot ,ro# 8e>as nstru*#ents and $o&ered at3'3 - ave been used' 8e #odulation is acieved b! a si#$le 27002 *6S transistor'

All te co#$onents ave been selected in order to reduce sie and $o&er consu#$tion- tus

obtainin% a co#$act and lo&*$o&er device- suitable ,or batter!*$o&ered o$erations' Kloball!- te

s!s*te# re@uires less tan 45 #A at 3'3 - al#ost e@uall! distributed bet&een te +luetoot

ear$one and te analo% ,ront*end' 8e ear*$one batter! as a ca$acit! o, 50 #A- tus te

c!cle batter! li,e o, te overall s!ste# is a$$ro>i#atel! 70 #in'

8o validate te $ro$osed a$$roac and to $rovide an e>a#$le o, a$$lication ,or a $ortable

device- a de#onstrative A$$ as been develo$ed ,or an Android s#art$one' 8e A$$ tas;s are to

ac@uire- store- elaborate- and so& te sensor si%nals' Data ac@uisition is si#$li,ied b! te use o,

te +luetoot inter,ace ,unctions $rovided b! te s#art$one o$eratin% s!ste# ten- ra& data are

saved as audio ,iles (&ave ,or#at) in te s#art$one #e#or!- ,or an o$tional o,,*line $ost

elaboration' 8e $rocessin% o, data includes te de#odulation o, te ac@uired audio si%nal- in

order to e>tract in,or#ation o, te PPK si%nal sa$e and to te carrier $eriod- &ic is related to

te tissue i#$edance' oreover- a si#$le evaluation o, te eart beat rate is $er,or#ed' 6btained

data are ten visual*ied on te s#art$one screen- as illustrated b! a screensot o, te

develo$ed A$$ in .i%' 10'


10/14

Fig. ). Di%ital sco$e ac@uisition o, te non*,iltered PPK sensor out$ut (Co,.i%' 4(a))'


11/14


12/14

Fig. +. Di%ital sco$e ac@uisition o, te ,iltered (PPKo,.i%' 4(a)) and #odulated (+8o,.i%' 4(b)) PPK sensor out$ut'

A' De$ari et al' Sensors and Actuators A202 (2013) 147154 153

Fig. 1,. Screenshot of the demo App implemented for an Androidsmartphone.

Fig. 11. O-line elaboration of an acquired le during a test of thesystem.

4. -onclusions

on*invasive and real*ti#e #easure#ent o, $!sical $ara#e*ters

re@uires a si#$le- $ortable and lo& cost s!ste# able to collect te

in,or#ation &itout inter,erin% &it atletic trainin%' A s!s*te#

co#$osed o, a +luetoot ear$one e@ui$$ed &it a PPK and tissue

i#$edance sensors- to be a$$lied on te earlobe o, te at*lete- as

been $ro$osed' 8an;s to an e,,ective $rocessin% o, te sensor data-

an audio si%nal- suitable to be trans#itted &it +lue*toot ear$ones

o$eratin% &it te standard ?ands*.ree $ro,ile- can be obtained'

8ere,ore- a broad ran%e o, $ortable devices- suc as s#art$ones

and tablets- can be used to ac@uire te sensor si%*nal- ,or real*ti#e

$rocessin%- data visualiation- and user inter,ace' Data obtained ,ro#

te esti#ation o, te eart beat rate and te earlobe i#$edance can

be used to $rovide to te atlete real*ti#e in,or#ation concernin% te

res$onse o, te bod! to te ,ati%ue- tus allo&in% te# to ad"ust is

activit!- avoidin% ealt ris;s and to i#$rove is $er,or#ance' 8e

#ulti*sensor $rotot!$e described


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and caracteried in te $a$er- alon% &it a de#o a$$lication ,or an

Android s#art$one- ave de#onstrated te ,easibilit! o, te $ro*

$osed a$$roac- #onitorin% te cardiac si%nal and te variations o,

u#an tissue i#$edance due to $!sical e,,ort'

e/erences

!1br0ken!! C.M. De Dominicis D. Ma!!otti M. "iccinelli S.#inaldi A. $e!!oli A. Depari %&aluation of bluetoothhands-free prolefor sensors applications in smart-phone platforms in' "roceedings of(%%% Sensors Applications Symposium )SAS* +,+ pp. +,+/.

!2br0ken!! A. Depari A. 0lammini S. #inaldi A. $e!!oli Aportable multi-sensor system for non-in&asi&e measurement ofbiometrical data in' "roceedings %ngineer-ing +1th %uropeanConference on Solid-State 2ransducers %3#OS%4SO# +,+ &ol. 567ra8o9 "oland September :+ +,+ pp. ;+;;+1http'L 0.. Eart %lectric properties of tis-sues Hiley

%ncyclopedia of iomedical %ngineering )+,,1* +http'


14/14


lessandra Flammini &as born in +rescia- tal!- in 1G0'Se received te 'Sc'de%ree (&it onours) in $!sics,ro# te niversit! o, /o#e- /o#e- tal!- in 15' .ro#15 to 15- se &as involved &it industrial researcand develo$#ent on di%ital drive control' Currentl!- se is&it te De$art#ent o, n,or#ation n%ineer*in%-niversit! o, +rescia- +rescia- tal!- &ere se &as a/esearcer ,ro# 15 to 2002 and as been an

Associate Pro,essor since 2002' Se teaces severalcourses about #easure#ents in industrial environ#ents

and di%ital electronic s!ste#s' ?er #ain researc activit!includes e#bedded s!ste#s- #easure#entinstru#entation- sensor si%nal $rocessin%- s#artsensors- &ired and &ireless sensor netin%- s!n*croniation and s#art %rids'

Ste/ano inaldi &as born in Seriate- tal!- in 12' ?e

received te de%ree &it onours in electronics

en%ineerin% in 200G and te P'D' de%ree in electronic

instru#entation in 2010 ,ro# te niversit! o, +rescia-+rescia- tal!' ?is #ain researc activities are ,ocused on$er,or#ance anal!sis o, industrial net- &irelesssensor net- s#art sensors- real*ti#e ternet-,ieldbus a$$lications- s!ncroniation #etods- .PKASoC desi%n- and Linu>*e#bedded so,t&are devel*o$#ent'

ngelo ezzoli &as born in Ciari in 13' ?e %raduatedin lectronics n%ineerin% at niversit! o, +rescia in2010 &it a tesis titled

Tugas Elins Journal-CONVERT2

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