Lecture 2 Sensors - About the Design Group | Mechanical...

EE/CS118 Sensors Lecture

Mechatronic Systems

DecisionMaking

Actuation

Worldto

Signal

TheWorld

MicroController


The World to Signal

Sensors or Transducers

Convert one physical phenomenon to another

Examples that you Encounter Daily


What can the Microcontroller Measure ?


Basic Sensors: Light

PhotoCells

CdS Resistance Varies with Incident LightMore Light = Lower Resistance

Spectral Response

Approximates Human Eye

Dynamic Response

Power Rating


CdS Photocell Specifications

O p to-sem icond uctors: Cd S Ph otocondu ctive CellsThese cel ls h ave a sp ectra l resp on se c lose to the h um an eye.

T y p e N o . P ac k age ( m m )

PeakS en s itiv ity

W av e le ng thp

(n m)

R e s is ta nc e

* 4 R is e T im e

t r0 t o 6 3 %

1 0 lx(m s)

F a ll T imetf

1 0 0 t o 3 710 l x(m s)

1 0 l x *2

M in . M a x. ( k )

0 lx * 3 M in .

(M )

P 1 1 1 4 - 0 4

M e t a l

T O - 1 8 57 0 1 5 t o 4 5 10 0 . 8 0 40 20

P 320

5 .5

52 0 3 5 t o 1 0 0 20 0 . 8 5 60 20

P 559 54 0 2 .9 t o 8 .5 0 .1 0 . 6 0 10 0 14 0

P 930 56 0 7 t o 2 3 0 .5 0 . 6 860

90

P 1 4 65 52 0 2 7 t o 8 1 10 0 . 8 5 20

* 1 : Dual element coating type. Listed data are for one element.* 2 : Measured with a tungsten lamp o f 2856K .* 3 : M easured 10 seco nds a fter remo val o f inc ident illuminate ion o f 1 0 /x

* 4: Gamma cha racteristics be tween 1 0l x and 100l x .R1 0, R1 0 0: C ell resistance va lues at 10l x and 10 0l x. Gamma characteristics varia tions of 0 .10 .

γ 1001 0 = log(R10/R100)

log(100/10)


CdS Photocells: How do you use them?

In a voltage divider to generate a voltage

R210k

5V

R1

R210k

Anywhere you can use a resistor to vary a circuit’s output



Photo-Transistors

NPN only

Light Replaces the base current

Spectral Response

Dynamic Response

Spectral sensitivity characteristics100

80

60

40

20

Wavelength (nm)700 800 900 1000 1100 1200

0600

VCE = 10V


0° 10° 20°

30°

40°

50°

60°

70°80°90°

Directivity characteristics

20

90

100

80

70

60

50

40

30 Rel

ativ

e se

nsiti

vity

S (%

)

Directional Characteristics

Sensitivity/Linearity

I CE(L) — L

Illuminance L (lx)

Col

lect

or p

hoto

cur

rent

I

CE(

L) (

mA

)

V CE = 10VTa = 25°CT = 2856K

10 3

10 2

10

1

10 –1

10 10 3 10 410 210 –21


LTR3208EData Sheet


Phototransistors: How Do You Use Them?

5V

R11k

Q1

5V

R11k

Q1

Simple Ways


Phototransistors: How Do You Use Them?Better Way

R110k

5V

R110k



Photo-Diodes

Spectral Sensitivity

Speed

Light Sensitivity


Wide Dynamic Range


LTR516ADData Sheet


Photodiodes: how Do You Use Them?

D1

R1100k


Basic Sensors: Magnetic Field

Simplest: a Reed Switch


Basic Sensors: Magnetic Field

Hall Sensors

Semiconductors

Switches

Analog


Uni-Polar

BiPolar

Linear


Linear SensorMeasuring Rotation

DigitalUsing Bias Magnet


Basic Sensors: TemperatureThermistors

Temperature Sensitive Resistor

Large ∆R for ∆T

Non-Linear

But well understood


Basic Sensors: Temperature

Platinuum Restive Temperature Devices

RTDs

Wide Temperature Range

Extremely Linear

Very Stable

Not Very Sensitive


• AVAILABLE IN 100, 500, 10 00, AND 2000 OHM RESISTANCE VALUES

• ST ANDARD IEC 751, AST ME1137 & NON-ST ANDARDTOLERANCES AVAILABLE

• WIDE CHOICE OF SIZES• 2, 3, AND 4 WIRE EXTENSION LEADS AVAILABLE• CUST OM -ENGINEERED T EMPERAT URE PROBE

ASSEMBLIES

PLATINUM THIN F ILM RTD ELEM ENTS

Sens or Scien tific, Inc. Platinum Thin Film RTD Elem en ts are fabricat -ed using s tate-of-the-art thin film process ing techniques , res ulting inan element of exceptional quality and s tability. The wide choice ofres is tance, to lerance , and s ize options a llows for com plete des ignflexibility.RTD elem en ts a re ava ilab le w ith extens ion leads , and inco rporated incom plete tem perature probe as sem blies . P lease contact Senso rScientific for additional inform ation.Assemblies: Generally, thin film RTD elem ents are incorporated into some type ofas sem b ly for p ro tection . Extens ion leads m ay be attached via so lder -ing, crim ping, brazing or welding. The attachment m ethod must becapable of withs tanding the intended maximum operating temperature.The following precautions mus t be taken when incorporating theelem ent into an as sem bly:1 ) Avoid s tra in ing the elem ent leads .2 ) If extens ion leads are attached via s oldering or brazing, all flux

res idue m us t be rem oved.3 ) The res is tance of extension leads m us t be taken in to cons idera tion.

Res is tance value at 0 °C ca librated 1m m from end o f lead w ire . 4 ) If elements are encaps ulated in a potting compound, insure that

the com pound will not induce pres sure loads, res ulting in a strain-gage effect.


Resis tance L W H at 0 Deg. C. Length Width He igh t Part Num ber

ohms mm mm mm100 5.0 +/- 0 .2 1 .0 +/- 0 .2 1.3 +/- 0 .2 P01 lln 1100 5 .0 +/- 0 .2 1 .5 +/- 0 .2 1.3 +/- 0 .2 P01 lln 2100 2 .3 +/- 0 .2 2 .0 +/- 0 .2 1.3 +/- 0 .2 P01 lln 3100 5 .0 +/- 0 .2 2 .0 +/- 0 .2 1.3 +/- 0 .2 P01 lln 4100 10.0 +/- 0 .2 2 .0 +/- 0 .2 1.3 +/- 0 .2 P01 lln 5100 5 .0 +/- 0 .2 4 .0 +/- 0 .2 1.3 +/- 0 .2 P01 lln 6100 1 .6+/- 0 .15 1.25 +/- 0.1 1 .00 +/- 0 .2 P01 ll M7500 5 .0 +/- 0 .2 2 .0 +/- 0 .2 1.3 +/- 0 .2 P05 lln 1500 10.0 +/- 0 .2 2 .0 +/- 0 .2 1.3 +/- 0 .2 P05 lln 2500 5 .0 +/- 0 .2 4 .0 +/- 0 .2 1.3 +/- 0 .2 P05 lln 3

1000 4 .0 +/- 0 .2 2 .0 +/- 0 .2 1.3 +/- 0 .2 P10 lln 11000 10.0 +/- 0 .2 2 .0 +/- 0 .2 1 .3 +/- 0 .2 P10 lln 21000 5 .0 +/- 0 .2 4 .0 +/- 0 .2 1.3 +/- 0 .2 P10 lln 31000 1 .6+/- 0 .15 1.25 +/- 0.1 1 .00 +/- 0 .2 P10 ll M42000 10.0 +/- 0 .2 2 .0 +/- 0 .2 1.3 +/- 0 .2 P20 lln 4

ll - To leranc e 0 B = D IN B n - Te m p era tu re R a nge01 =1 /1 0 D IN B at 0 °C 0 5 = A S TM B L = -50 to + 4 00 D e g C0 2 = 1 /5 D IN B a t 0 °C 06 = 3 /2 D IN B a t 0° C M = -5 0 t o + 55 0 D eg C0 3 = 1 /4 D IN B a t 0 °C 07 = 2 D IN B at 0 °C H = -5 0 to + 6 00 D e g C0 4 = 1 /3 D IN B a t 0 °C 08 = 5 D IN B at 0 °C0A = 1/2 D IN B (D IN A) at 0 °C 0 9 = 10 D IN B a t 0 °C

R es is tanc e v a lue at 0 °C ca libra te d 1m m f rom e nd o flea d wire. D IN = IEC 751

Limited Range of Resistances

∆R proportional to R at 0°C


Measuring Position

Translate Movement to ??? To Voltage

What are examples of ???


Optical Sensors for Position

Reflective


Optical Sensors for Position

Transmissive


Encoders For Position Sensing

Combine the TransmissiveOptical Sensor

With a rotating Mask


Encoder: How it works

Quadrature


Encoders: Where Do You Find Them?

Printers

Disk Drives

Lecture 2 Sensors - About the Design Group | Mechanical...

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