accelerometer - Saba Web Pagesaba.kntu.ac.ir/.../projects/presentations/accelerometer.pdf · piezoelectric sensors (without built-in electronics) ... Accelerometer Selection: Measurement

AccelerometerAccelerometerSensorsSensors

K.N.T. University of Technology

Presented by:Presented by:Mohammad ZandMohammad Zand

Seyed Mohammad Javad MoghimiSeyed Mohammad Javad Moghimi

OutlineOutline::Accelerometer IntroductionAccelerometer Introduction– Background– Device market– Types

TheoryTheory–– Capacitive sensorCapacitive sensor–– Piezoelectric sensorPiezoelectric sensor

Signal ConditioningSignal Conditioning–– Conditioning CircuitsConditioning Circuits–– Standard ICsStandard ICs

MiscellaneousMiscellaneous–– Extra Information Extra Information –– Sensor ManufacturesSensor Manufactures–– ConclusionsConclusions–– ReferencesReferences

Background:MEMS– Micro Electro Mechanical Systems– Small devices that perform the same function

as larger mechanical systems– Usually “machined” out of silicon

Accelerometers– Devices that are used to measure

acceleration– Used for airbag sensors, etc.

Device Market:Primary Market– Automobile Airbag Sensors

– Approximately 50 million sensors/year

– Sensors sell for approximately $10 each

Secondary Markets– Computer Joysticks

– Military Applications

– Amusement Park Technology

Types:Types:1.1. PotentiometricPotentiometric

2.2. LVDTLVDT

3.3. Variable ReluctanceVariable Reluctance

4.4. PiezoresistivePiezoresistive

5.5. CapacitiveCapacitive

6.6. PiezoelectricPiezoelectric

capacitive transducers strain gage transducers optical transducers (laser interference measurement) resistive transducers electromagnetic transducers

Piezoelectric Types:Piezoelectric Types:i.i. Shear systemShear system

ii.ii. Compression systemCompression system

iii.iii. Bending or Flexure systemBending or Flexure system

Piezoelectric Advantages:Piezoelectric Advantages:1.1. Extremely wide dynamic range, almost free of noise Extremely wide dynamic range, almost free of noise -- suitable for shock suitable for shock

measurement as well as for almost imperceptible vibration.measurement as well as for almost imperceptible vibration.

2.2. Excellent linearity over their dynamic range.Excellent linearity over their dynamic range.

3.3. Wide frequency range, high frequencies can be measured.Wide frequency range, high frequencies can be measured.

4.4. Compact yet highly sensitive. Compact yet highly sensitive.

5.5. No moving parts No moving parts -- no wear. no wear.

6.6. SelfSelf--generating generating -- no external power required. no external power required.

7.7. Great variety of models available for nearly any purpose. Great variety of models available for nearly any purpose.

8.8. Integration of the output signal provides velocity and displacemIntegration of the output signal provides velocity and displacement.ent.

Comparing Piezoelectric with others:Comparing Piezoelectric with others:

-- low resolutionlow resolution

-- fragilefragile-- measures static accelerationmeasures static acceleration

-- cheap manufacturing with cheap manufacturing with semiconductor technologysemiconductor technology

CapacitiveCapacitive

-- only for low frequenciesonly for low frequencies-- also for static measurement also for static measurement ElectrodynamicElectrodynamic

-- limited resolution because of limited resolution because of resistive noiseresistive noise

-- only for low and medium only for low and medium frequenciesfrequencies

-- supply voltage requiredsupply voltage required

-- measures static accelerationmeasures static accelerationPiezoresistivePiezoresistive

DisadvantageDisadvantageAdvantageAdvantageSensor TypeSensor Type

Comparing Piezoelectric Types:Comparing Piezoelectric Types:

-- fragilefragile

-- relatively high relatively high temperature temperature transient sensitivitytransient sensitivity

-- high temperature high temperature transient sensitivitytransient sensitivity

-- high base strain high base strain sensitivitysensitivity

-- lower sensitivitylower sensitivity--toto--mass ratio mass ratio

DrawbackDrawback

-- best sensitivitybest sensitivity--toto--mass ratio mass ratio

-- high sensitivityhigh sensitivity--toto--mass ratiomass ratio

-- robustnessrobustness

-- technological technological advantagesadvantages

-- low temperature low temperature transient sensitivitytransient sensitivity

-- low base strain low base strain sensitivitysensitivity

AdvantageAdvantage

BendingBendingCompressionCompressionShearShear

Theory: Capacitive sensorTheory: Capacitive sensor

Two Objects in SpaceParallel Plate Capacitor

Change in Capacitance due to the Lateral Movement of the Plates

Change in Capacitance due to the Change in Plate Separation

Differential CapacitorA General Accelerometer

Theory: Piezoelectric sensorTheory: Piezoelectric sensor

Q (charge) = d F

Rx = Resistance of piezo Cx = Capacitance of piezo Cc = Capacitance of cable

Ca = Capacitance of amplifier circuit Ra = Resistance of amplifier circuitUseful frequency range

Charge amplifying circuit

Conditioning Circuit: CapacitiveConditioning Circuit: Capacitive

Conditioning Circuit: PiezoelectricConditioning Circuit: PiezoelectricCharge Output Sensors Charge Output Sensors -- high output impedance, high output impedance, piezoelectric sensors (without builtpiezoelectric sensors (without built--in electronics) in electronics) which typically require external charge or voltage which typically require external charge or voltage amplifiers for signal conditioning. amplifiers for signal conditioning. Internally Amplified Sensors Internally Amplified Sensors -- low impedance, low impedance, piezoelectric force, acceleration and pressure type piezoelectric force, acceleration and pressure type sensors with builtsensors with built--in integrated circuits. (ICPin integrated circuits. (ICP®® is is registered trademark of PCB registered trademark of PCB PiezotronicsPiezotronics, Inc. which , Inc. which uniquely identifies PCB's sensors which incorporate uniquely identifies PCB's sensors which incorporate builtbuilt--in electronics.) in electronics.)

Conditioning Circuit: PiezoelectricConditioning Circuit: Piezoelectric

-- Limited cable length (< 10Limited cable length (< 10 m)m)

-- Special low noise cable Special low noise cable requiredrequired

-- Charge amplifier requiredCharge amplifier required

-- Constant current excitation required Constant current excitation required (reduces battery operating hours)(reduces battery operating hours)

-- Inherent noise sourceInherent noise source

-- Upper operating temperature limited to Upper operating temperature limited to <120<120 °°CC

DrawbackDrawback

-- No power supply required No power supply required --ideal for battery powered ideal for battery powered equipmentequipment

-- No noise, highest resolutionNo noise, highest resolution

-- Wide dynamic rangeWide dynamic range

-- Higher operating Higher operating temperaturestemperatures

-- Smaller sensors possibleSmaller sensors possible

-- Fixed sensitivity regardless of cable Fixed sensitivity regardless of cable length and cable qualitylength and cable quality

-- LowLow--impedance output can be impedance output can be transmitted over long cables in harshtransmitted over long cables in harshenvironmentsenvironments

-- Inexpensive signal conditioners and Inexpensive signal conditioners and cablescables

-- Intrinsic selfIntrinsic self--test functiontest function

-- Withstands better harsh conditions like Withstands better harsh conditions like dirt and humiditydirt and humidity

AdvantageAdvantage

Charge Mode SensorsCharge Mode SensorsICPICP®® Compatible SensorsCompatible Sensors

Conditioning Circuit: PiezoelectricConditioning Circuit: PiezoelectricICPICP®® principleprinciple

Conditioning Circuit: PiezoelectricConditioning Circuit: Piezoelectric

Charge Amplified System Schematic

Standard ICs:Standard ICs:MAX1455 (MAXIM)MAX1455 (MAXIM)

Extra Information:Extra Information:Accelerometer MountingAccelerometer MountingAccelerometer CablingAccelerometer CablingAccelerometer Selection (Metra Mess)Accelerometer Selection (Metra Mess)MEMSMEMSDatasheetsDatasheetsApplicationsApplicationsMore about signal conditioningMore about signal conditioningTEDSTEDS

Availability in IRAN:Availability in IRAN:: : مجتمع الکترونيک سيليکون مجتمع الکترونيک سيليکون

((www.siliconec.comwww.siliconec.com))(([email protected]@Yahoo.com))Tele Fax:+98 21 6712720 (5 Lines)Tele Fax:+98 21 6712720 (5 Lines)

ADXL202 (Analog Devices) ADXL202 (Analog Devices) 400,000 400,000 RialsRials

ADXL210 ADXL210 (Analog Devices)(Analog Devices)490,000 490,000 RialsRials

Sensor Manufactures:Sensor Manufactures:

Conclusions:Conclusions:There are so many types of There are so many types of accelerometers for so many applications.accelerometers for so many applications.

ItIt’’s applications extends in many tasks.s applications extends in many tasks.

The price varies between a few ten dollars The price varies between a few ten dollars to few thousand dollars.to few thousand dollars.

MEMS version is smaller, lighter, and cheaper than traditional alternatives.

References:References:1.1. Stanford universityStanford university

2.2. MIT university MIT university

3.3. Metra MessMetra Mess-- und und FrequenztechnikFrequenztechnik RadebeulRadebeul

4.4. PCB PCB PiezotronicsPiezotronics

5.5. National InstrumentsNational Instruments

6.6. Berkeley UniversityBerkeley University

7.7. ENDEVCO Corporation ENDEVCO Corporation

8.8. Sensorland.comSensorland.com

9.9. Honeywell InternationalHoneywell International

10.10. Analog DevicesAnalog Devices

11.11. MaximMaxim

12.12. DelphiDelphi

Questions?Questions???

Accelerometer MountingAccelerometer Mounting::

Mounting methods for accelerometers

a Accelerometer probeb Insulating flangec Magnetic clampd Adhesive mounting (no wax)e Stud mounting

Resonance frequencies of different mounting methods

Typical reasons of coupling errors

Accelerometer CablingAccelerometer Cabling::

Methods of cable tie-down Sensor mounting without insulation causes a ground loop Insulated sensor mounting avoids ground loops

Accelerometer SelectionAccelerometer Selection::

Single and double integration, below 20 Hz use shear type accelerometersMeasurement of Vibration Velocity and Displacement

Industrial accelerometers with protection grade IP67Humidity and Dust

Assess influence, choose sensor according to characteristics,choose shear type accelerometers when temperature transients or base strain may occur, stainless steel versions forstrong magnetic fields

Temperature Transients, Base Strain, MagneticFields, Extreme Acoustic Noise

KB12(V)KS48

KD41/42(V)KS50-52KS813KS513KS80

KS76/77KD37/38(V)

KB103KS74

KD29KD93KS943

KS91/93KS94/95

> 100 g50 - 100 g20 - 50 g3 - 20 g< 3 g

Accelerometer weight <1/10 the weight of test object.Choose miniature accelerometers for light objects.Selection chart for sensor weight:

Weight of Test Object

KS91KD93

KS76/77KS93/94/95

KD29KS943KS74

KD37/38(V)KS50-52KS513KS80

KD41/42(V)KS48

KS813KB103

KB12(V)

> 25 kHz15 - 25 kHz10 - 15 kHz0,2 - 10 kHz< 200 Hz

Choose resonant frequency and linear frequency rangeSelection chart for upper 3 dB frequency limit:

Frequency Range

KD29KD93

KS93KS50-52KD37-42

KS91/94/95KS513KS943

KS76/77KD37V-42V

KB103KS813

KS74/80

KB12(V)KS48

> 10 000 g1000 - 10000 g200 - 1000 g10 - 200 g < 10 g

Selection chart for acceleration:

Amplitude Range

Accelerometer PropertiesCriteria

MEMS:MEMS:

Datasheets:Datasheets:QQ--FlexFlex®® QA3000 (QA3000 (HonywellHonywell))

MEMS MS7000 (MEMS MS7000 (ColibrysColibrys))

GPGP--383 (Columbia Research 383 (Columbia Research Laboratories, Inc)Laboratories, Inc)

ADXL202E(Analog Devices)ADXL202E(Analog Devices)

Model 66A50 Model 66A50 TEDS(EndevcoTEDS(Endevco))

APA300 (Star Micronics America, INC)APA300 (Star Micronics America, INC)

ApplicationsApplications::

More about signal conditioningMore about signal conditioning::Metra Mess:Metra Mess:

Charge Amplifiers M68 SeriesCharge Amplifiers M68 SeriesICPICP®® Conditioning Module M32Conditioning Module M32

TEDS:TEDS:

ENDEVCO®:i-TEDS AccelerometerModel 66A50, A11, A12

• Smallest Triax with TEDS• IEEE P1451.4 TEDS

• Light Weight (5.5 gm)• Single Cable

• Milli-g's Resolution• Hermetically Sealed• Titanium Housing

• Case Isolation Option