Sensors for Low Level Signal Acquisition (Design Conference 2013)

Sensors for Low Level Signal Acquisition Advanced Techniques of Higher Performance Signal Processing

Legal Disclaimer

Notice of proprietary information, Disclaimers and Exclusions Of Warranties The ADI Presentation is the property of ADI. All copyright, trademark, and other intellectual property and proprietary rights in the ADI Presentation and in the software, text, graphics, design elements, audio and all other materials originated or used by ADI herein (the "ADI Information") are reserved to ADI and its licensors. The ADI Information may not be reproduced, published, adapted, modified, displayed, distributed or sold in any manner, in any form or media, without the prior written permission of ADI. THE ADI INFORMATION AND THE ADI PRESENTATION ARE PROVIDED "AS IS". WHILE ADI INTENDS THE ADI INFORMATION AND THE ADI PRESENTATION TO BE ACCURATE, NO WARRANTIES OF ANY KIND ARE MADE WITH RESPECT TO THE ADI PRESENTATION AND THE ADI INFORMATION, INCLUDING WITHOUT LIMITATION ANY WARRANTIES OF ACCURACY OR COMPLETENESS. TYPOGRAPHICAL ERRORS AND OTHER INACCURACIES OR MISTAKES ARE POSSIBLE. ADI DOES NOT WARRANT THAT THE ADI INFORMATION AND THE ADI PRESENTATION WILL MEET YOUR REQUIREMENTS, WILL BE ACCURATE, OR WILL BE UNINTERRUPTED OR ERROR FREE. ADI EXPRESSLY EXCLUDES AND DISCLAIMS ALL EXPRESS AND IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT OF ANY THIRD PARTY INTELLECTUAL PROPERTY RIGHTS. ADI SHALL NOT BE RESPONSIBLE FOR ANY DAMAGE OR LOSS OF ANY KIND ARISING OUT OF OR RELATED TO YOUR USE OF THE ADI INFORMATION AND THE ADI PRESENTATION, INCLUDING WITHOUT LIMITATION DATA LOSS OR CORRUPTION, COMPUTER VIRUSES, ERRORS, OMISSIONS, INTERRUPTIONS, DEFECTS OR OTHER FAILURES, REGARDLESS OF WHETHER SUCH LIABILITY IS BASED IN TORT, CONTRACT OR OTHERWISE. USE OF ANY THIRD-PARTY SOFTWARE REFERENCED WILL BE GOVERNED BY THE APPLICABLE LICENSE AGREEMENT, IF ANY, WITH SUCH THIRD PARTY. ©2013 Analog Devices, Inc. All rights reserved.

2

Today’s Agenda

Sensors are the source

Sensor signals are typically low level and difficult

Signal conditioning is key to high performance

Silicon sensors are integrated with signal conditioning

Applications keep demanding higher accuracy

Motion sensors with moving silicon elements are driving systems in all market areas

3

The Goal

Capture what is going on in the real world

Convert into a useful electronic format

Analyze, manipulate, store, and send

Return to the real world

4

The Real World Is NOT Digital

5

Analog to Electronic Signal Processing

6

SENSOR (INPUT)

DIGITAL PROCESSOR AMP CONVERTER

ACTUATOR (OUTPUT)

AMP CONVERTER

The Sensor

7

SENSOR (INPUT)

DIGITAL PROCESSOR AMP CONVERTER

ACTUATOR (OUTPUT)

AMP CONVERTER

Analog, but NOT electronic

Analog AND electronic

Popular Sensors

Sensor Type Output

Thermocouple Voltage

Photodiode Current

Strain gauge Resistance

Microphone Capacitance

Touch button Charge output

Antenna RF signals

Acceleration Capacitance

8

Sensor Signal Conditioning

9

SENSOR AMP

Analog, electronic, but “dirty”

Analog, electronic, and “clean”

Amplify the signal to a noise-resistant level

Lower the source impedance

Linearize (sometimes but not always)

Filter

Protect

Designing Sensors in Silicon

Sensor signals are typically low level and subject to noise coupling on connections to amplifiers

Bring signal conditioning as close to sensor as possible Multichip hybrids Silicon sensor on same chip as amplifier/data converter

Environmental issues Extreme temperature or vibration Sensor needs to be small for sensitivity

Finding silicon property that responds to physical variable Capacitance, stress, temperature change

10

Silicon Sensors

Sensor Type Output

Temperature Voltage/current

Photodiode Current

Strain gauge Resistance

Microphone Capacitance

Rotation Capacitance

Antenna RF signals

Acceleration Capacitance

11

Types of Temperature Sensors

12

THERMOCOUPLE RTD THERMISTOR SEMICONDUCTOR

Widest Range:

–184ºC to +2300ºC

Range:

–200ºC to +850ºC

Range:

0ºC to +100ºC

Range:

–55ºC to +150ºC

High Accuracy and

Repeatability

Fair Linearity Poor Linearity Linearity: 1ºC

Accuracy: 1ºC

Needs Cold Junction

Compensation

Requires

Excitation

Requires

Excitation

Requires Excitation

Low-Voltage Output Low Cost High Sensitivity 10mV/K, 20mV/K,

or 1µA/K TypicalOutput

Basic Relationships for Semiconductor Temperature Sensors

13

IC IC

VBE VN

∆VBE VBE VNkTq

N= − = ln( )

VBEkTq

ICIS

=

ln

=

S

CN IN

Iq

kTV×

ln

INDEPENDENT OF IC, IS

ONE TRANSISTOR N TRANSISTORS

Classic Band Gap Temperature Sensor

14

"BROKAW CELL" R R

+ I2 ≅ I1

Q2 NA

Q1 A

R2

R1

VN VBE (Q1)

VBANDGAP = 1.205V

+VIN

VPTAT = 2 R1 R2

kT q ln(N)

∆VBE VBE VNkTq

N= − = ln( )

Analog Temperature Sensors

15

Product Accuracy (Max)

Max Accuracy Range

Operating Temp Range

Supply Range

Max Current Interface Package

AD590 ±0.5°C ±1.0°C

25°C −25°C to +105°C

−55°C to +150°C

4 V to 30 V 298 µA Current out TO-52, 2-lead FP, SOIC, Die

AD592 ±0.5°C ±1.0°C

25°C −55°C to +150°C

−25°C to +105°C

4 V to 30 V 298 µA

Current out TO-92

TMP35 ±2.0°C 0°C to 85°C −25°C to +100°C

−55°C to +150°C

2.7 V to 5.5 V 50 µA

Voltage out TO-92, SOT23, SOIC

TMP36 ±3.0°C −40°C to +125°C

−55°C to +150°C

2.7 V to 5.5 V 50 µA

Voltage out TO-92, SOT23, SOIC

AD221100

±2.0°C −50°C to +150°C

−55°C to +150°C

4 V to 6.5 V 650 µA

Voltage out TO-92, SOIC, Die

AD22103

±2.5°C 0°C to +100°C

0°C to +100°C

2.7 V to 3.6 V 600 µA

Voltage out TO-92, SOIC

Digital Temperature Sensors Comprehensive Portfolio of Accuracy Options

16

Product Accuracy (Max) Max Accuracy Range Interface Package

ADT7420/ADT7320 ±0.2°C ±0.25°C

−10°C to +85°C −20°C to +105°C I2C/SPI LFCSP

ADT7410/ADT7310 ±0.5°C −40°C to +105°C I2C/SPI SOIC

ADT75 ±1°C (B grade) ±2°C (A grade)

0°C to 85°C −25°C to +100°C I2C MSOP, SOIC

ADT7301 ±1°C

0°C to 70°C SPI SOT23, MSOP

TMP05/TMP06 ±1°C

0°C to 70°C PWM SC70, SOT23

AD7414/ADT7415 ±1.5°C

−40°C to +70°C I2C SOT23, MSOP

ADT7302 ±2°C 0°C to 70°C SPI SOT23, MSOP

TMP03/TMP04 ±4°C

−20°C to +100°C

PWM TO-92, SOIC, TSSOP

High Accuracy Temperature Sensing Applications Scientific, medical and aerospace Instrumentation Medical equipment Laser beam positioners

Test and measurement Calorimeters Automatic test equipment Mass spectrometry Thermo cyclers/DNA analyzers Infrared imaging Data acquisition/analyzers Flow meters

Process control Instruments/controllers

Critical asset monitoring Food and pharmaceutical

Environmental monitoring 17

17

Digital IC RTD Thermistor

Ease of Use

Sensor selection and sourcing

Reliable supply and specifications

Need to determine reliable suppliers (specifications std.)

Need to determine reliable suppliers and specifications

Extra signal processing Additional sourcing, selection, design, evaluation, testing, manufacturing

No

Precision ADC (≥16 bits) Current source Amp (optional) Precision resistor Filter caps

ADC (resolution is app specific) Current source Amp (optional) Precision resistor Filter caps

Linearization No Yes Yes

Calibration No Yes Yes Resistance concerns No Yes Yes Self heating concerns No Yes Yes

Reliability Contact resistance No Susceptible Susceptible

Batch variation No Susceptible Susceptible Transmission noise No Susceptible Susceptible

Performance Accuracy range Industrial Range Wide range Commercial range

Stability High High Low

Repeatability High High Low

High Performance Temperature Measurement Sensor Comparison d

18

High Accuracy Temperature Measurement Sensor Comparison

Sensor Type NTC Thermistor PT100 RTD (Thin Film)

Digital IC ADT7X20

*Accuracy

±0.1°C from 0 to 70°C ±0.3°C from 0 to 100°C

Excludes: Data conversion

Signal conditioning Self heating, noise, drift etc.

±0.27°C from 0 to 100° (Class 1/3 B)

Excludes: Data conversion

Signal conditioning Self heating

Lead wire resistance Noise, etc.

±0.2°C from −10 to +85°C ±0.25°C from −20 to +105°C

Linearity Poor Medium to high High

Thermal response Medium to fast Medium to fast Medium to fast

Long term stability/reliability Low Medium to high High

System cost High for low tolerance (±0.1/0.2°C) High Low

Calibration required Yes Yes No

Extra components required Yes Yes No

19 *For thermistors and RTDs actual tolerances will degrade in assembled system.

Thermocouple

Very low level (µV/ºC)

Nonlinear

Difficult to handle

Wires need insulation

Susceptible to noise

Fragile

20

Common Thermocouples

21

Junction Materials Typical Useful Range (°C)

Nominal Sensitivity (µV/°C)

ANSI Designation

Platinum (6%)/Rhodium- Platinum (30%)/Rhodium

38 to 1800 7.7 B

Tungsten (5%)/Rhenium- Tungsten (26%)/Rhenium

0 to 2300 16 C

Chromel-Constantan 0 to 982 76 E

Iron-Constantan 0 to 760 55 J

Chromel-Alumel −184 to +1260 39 K

Platinum (13%)/Rhodium- Platinum

0 to 1593 11.7 R

Platinum (10%)/Rhodium- Platinum

0 to 1538 10.4 S

Copper-Constantan −184 to +400 45 T

Thermocouple Output Voltages for Type J, K, and S Thermocouples

22

-250 0 250 500 750 1000 1250 1500 1750-10

0

10

20

30

40

50

60

THER

MO

CO

UP

LE O

UTP

UT

VOLT

AG

E (m

V)

TEMPERATURE (°C)

TYPE JTYPE K

TYPE S

-250 0 250 500 750 1000 1250 1500 1750-10

0

10

20

30

40

50

60

THER

MO

CO

UP

LE O

UTP

UT

VOLT

AG

E (m

V)

TEMPERATURE (°C)

TYPE JTYPE K

TYPE S

Thermocouple Seebeck Coefficient vs. Temperature

23

-250 0 250 500 750 1000 1250 1500 17500

10

20

30

40

50

60

70

SEEB

ECK

CO

EFFI

CIE

NT

-µV/

°C

TEMPERATURE (°C)

TYPE J

TYPE K

TYPE S

-250 0 250 500 750 1000 1250 1500 17500

10

20

30

40

50

60

70

SEEB

ECK

CO

EFFI

CIE

NT

-µV/

°C

TEMPERATURE (°C)

TYPE J

TYPE K

TYPE S

Thermocouple Basics

24

T1

METAL A

METAL B

THERMOELECTRIC EMF

R METAL A METAL A

R = TOTAL CIRCUIT RESISTANCE I = (V1 – V2) / R

V1 T1 V2 T2

V1 – V2

METAL B

METAL A METAL A

V1

V1

T1

T1

T2

T2

V2

V2

V METAL A METAL A

COPPER COPPER

METAL B METAL B

T3 T4

V = V1 – V2, IF T3 = T4

A. THERMOELECTRIC VOLTAGE

B. THERMOCOUPLE

C. THERMOCOUPLE MEASUREMENT

D. THERMOCOUPLE MEASUREMENT

I

V1 T1

METAL A

METAL B EMF

R METAL A METAL A

R = TOTAL CIRCUIT RESISTANCE I = (V1 – V2) / R

V1 T1 V2 T2

V1 – V2

METAL B

METAL A METAL A

V1

V1

T1

T1

T2

T2

V2

V2

V METAL A

COPPER COPPER

METAL B METAL B

T3 T4

V = V1 – V2, IF T3 = T4

A. THERMOELECTRIC VOLTAGE

B. THERMOCOUPLE

C. THERMOCOUPLE MEASUREMENT

D. THERMOCOUPLE MEASUREMENT

I

V1

Using a Temperature Sensor for Cold-Junction Compensations

25

TEMPERATURECOMPENSATION

CIRCUIT

TEMPSENSOR

T2V(T2)T1 V(T1)

V(OUT)V(COMP)

SAMETEMP

METAL A

METAL B

METAL A

COPPERCOPPER

ISOTHERMAL BLOCKV(COMP) = f(T2)

V(OUT) = V(T1) – V(T2) + V(COMP)

IF V(COMP) = V(T2) – V(0°C), THEN

V(OUT) = V(T1) – V(0°C)

TEMPERATURECOMPENSATION

CIRCUIT

TEMPSENSOR

T2V(T2)T1 V(T1)

V(OUT)V(COMP)

SAMETEMP

METAL A

METAL B

METAL A

COPPERCOPPER

ISOTHERMAL BLOCKV(COMP) = f(T2)

V(OUT) = V(T1) – V(T2) + V(COMP)

IF V(COMP) = V(T2) – V(0°C), THEN

V(OUT) = V(T1) – V(0°C)

Thermocouple Amplifiers AD849x Product Features and Description Factory trimmed for Type J and K thermocouples Calibrated for high accuracy

Cold Junction Compensation (CJC) IC temps of 25°C and 60°C

Output voltage of 5 mV/°C Active pull-down Rail-to-Rail output swing

Wide power supply range +2.7 V to ±15 V Low power < 1 mW typical Package–space saving MSOP-8, lead-free Low cost < $1 in volume Can measure negative temperatures in single-supply operation

26

Part Number Thermocouple Type

Optimized Temp Range

Measurement Temp Range

Initial Accuracy

AD8494 J 0 to 50°C Full J type range ±1°C and ±3°C

AD8495 K 0 to 50°C Full K type range ±1°C and ±3°C

AD8496 J 25°C to 100°C Full J type range ±1.5°C and ±3°C

AD8497 K 25°C to 100°C Full K type range ±1.5°C and ±3°C

Demo Using a Temperature Sensor for Cold-Junction Compensations–CN0271 Figure 1. K-type thermocouple measurement system with integrated

cold junction compensation (simplified schematic: all connections not shown)

27

AD8495

OUT

SENSE

REF –VS

+VS+VS

–VS

INP

INN

0.1µF 10µF

+5V

+2.5V

COLDJUNCTION

COMPENSATION

THERMO-COUPLE

1MΩ 100Ω49.9kΩ0.01µF

0.01µF

1.0µF100Ω

0.1µF 0.1µF10µF

+5V +2.5V

IN-AMP

+OUT

–OUT

AD8476

10kΩ

10kΩ

10kΩ

10kΩ

100Ω 0.01µF

0.01µF

1.0µF100Ω SERIAL

INTERFACE

INTERNALCLOCK

16-BITADC

GND

REFIN

AD7790

DIGITALPGABUF

VDDVDD

GND

+5VADR441+5V

+2.5VVIN VOUTGND

1059

8-00

1

High Accuracy Applications Thermocouple Cold-Junction Compensation Benefits High accuracy High accuracy, 0.25C, low drift cold junction measurement using

ADT7320/7420 Fast throughput Parallel measurement of hot and cold junction gives fastest throughput

Flexibility Software-based solution

enabling use of multiple thermocouple types

Easy implementation Fully integrated digital

temp measurement solution

Low cost No costly multipoint

cold-junction calibration required

28

High Accuracy Applications CJC using ADT7320

29

ADT7320 for cold- junction temperature measurement

Thermocouple isothermal connector

ADT7320 mounted on Flex PCB

Σ-Δ ADC

Temperature Measurement RTD Sensor

Key application benefits 3-wire RTD 2 matched excitation currents 24-bit ADC resolution 40 nV RMS at gain = 64 Ratiometric configuration 50 Hz and 60 Hz rejection (−75 dB)

30

RL1

RL2

RL3

RTD

GND VDD

AD7793

SERIALINTERFACE

ANDCONTROL

LOGIC

INTERNALCLOCK

CLK

SIGMADELTAADC

IOUT1

MUXIN-AMP

REFIN(+) REFIN(-)BANDGAPREFERENCE

GND

SPI SERIALINTERFACE

IOVDD

VDD

GND

IOUT2

REFIN

AIN1

RREFEXCITATIONCURRENTS

High Impedance Sensors

Photodiodes

Piezoelectric sensors Accelerometers Hydrophones

Humidity monitors

pH monitors

Chemical sensors

Smoke detectors

Charge coupled devices

Contact image sensors for imaging

31

Photodiode Applications

Optical: light meters, auto focus, flash controls

Medical: CAT scanners (X-ray detection), blood particle analyzers

Automotive: headlight dimmers, twilight detectors

Communications: fiber optic receivers

Industrial: bar code scanners, position sensors, laser printers

32

Photodiode Equivalent Circuit

33

PHOTO CURRENT

IDEAL DIODE

INCIDENT LIGHT

RSH(T) 100kΩ - 100GΩ

CJ

Note: RSH halves every 10°C temperature rise

Photodiode Modes Of Operation

Photovoltaic Zero bias No “dark" current Linear Low noise (Johnson) Precision applications

Photoconductive Reverse bias Has “dark" current Nonlinear Higher noise (Johnson + shot) High speed applications

34

–

+

–VBIAS

–

+

Photodiode Specifications Silicon Detector Part Number SD-020-12-001 Area: 0.2 mm2

Capacitance: 50 pF

Shunt resistance at 25°C: 1000 mW

Maximum linear output current: 40 µA

Response time: 12 ns

Photosensitivity: 0.03 µA/foot candle (fc)

35

Short Circuit Current vs. Light Intensity for Photodiode (Photovoltaic Mode)

36

Environment Illumination (fc) Short Circuit Current

Direct sunlight 1000 30 µA Overcast day 100 3 µA

Twilight 1 0.03 µA Full moonlit night 0.1 3000 pA

Clear night/no moon 0.001 30 pA

Current-to-Voltage Converter (Simplified)

37

ISC = 30pA (0.001 fc)

+

_

R = 1000MΩ

VOUT = 30mV

SENSITIVITY: 1mV / pA

Preamplifier DC Offset Errors

38

~

VOS

IB

IB

R1

R2 1000MΩ

+

_

IB doubles every 10°C temperature rise R1 = 1000 MΩ at 25°C (diode shunt resistance) R1 halves every 10°C temperature rise

DC NOISE GAIN = 1 + R2 R1

OFFSET RTO

R3

R3 cancellation resistor not effective

Photodiode Amplifier Design Choices

40

Photodiode Amplifier Design Result

41

Complete Photodiode Sensing Application CN0272 Figure 1. Photodiode preamp system with dark current

compensation (simplified schematic: all connections and decoupling not shown)

42

AVDD

CF

RF

RF

0.1µF0.1µF

3.3pF

VBIAS–5V

+1.8V

+0.9V

22pF

AD8065

SFH 2701

AD9629-20

VIN–

VIN+VCM

INP

INN

VOCM

+2.5V+OUT

–OUT

AD8475

1kΩ

2.5kΩ

24.9kΩ

24.9kΩ2.5kΩ

1kΩ

33Ω

33Ω

+5V

–5V

+5V

–5V

TP3

TP2

ADR441+5V

+2.5VVIN VOUTGND

GND

TP1

1059

9-00

1

Tweet it out! @ADI_News #ADIDC13

Visit the Dual Channel Spectroscopy/Colorimetry Demo Board in the Exhibition Room

43

Circuit Features Three modulated LED drivers Two photodiode receive channels Programmable gain

Circuit Benefits Ease of use Self contained solution Dual channel 16-bit ADC for data

analysis

Complete Design Files Schematic Bill of Material PADs Layout Gerber Files Assembly Drawing

EVAL-SDP-CB1Z

EVAL-CN0312-SDPZ

This demo board is available for purchase: www.analog.com/DC13-hardware

http://www.analog.com/DC13hardware

Sensor Resistances Used in Bridge Circuits Span a Wide Dynamic Range

44

Strain gages 120Ω, 350 Ω, 3500 Ω

Weigh scale load cells 350 Ω to 3500 Ω

Pressure sensors 350 Ω to 3500 Ω

Relative humidity 100 kΩ to 10 mΩ

Resistance temperature devices (RTDs) 100 Ω, 1000 Ω

Thermistors 100 Ω to 10 mΩ

For more information and demonstration of bridge sensors, attend the Instrumentation – Sensing 2 – session.

Position and Motion Sensors

Linear position: linear variable differential transformers (LVDT)

Hall effect sensors Proximity detectors Linear output (magnetic field strength)

Rotational position: Optical rotational encoders Synchros and resolvers Inductosyn® sensors (linear and rotational position) Motor control applications

Acceleration and tilt: accelerometers

Gyroscopes

45

46

MEMS Sensors are Everywhere

Health and Fitness Products

Smartphones

Automotive Safety and Infotainment

Precision Agriculture

Avionics and Navigation

Fleet Management

Asset Tracking

What you can measure:

47


48

Linear Motion

ADI’s Motion Signal Processing ™ Enables… Motion Sensing

49

Fleet management

Alarm systems

Motion control and orientation of industrial robots

Precision agriculture


50

Tilt

51

ADI’s Motion Signal Processing ™ Enables… Tilt Sensing

Leveling

Horizon detection in cameras


52

Vibration & Shock

53

ADI’s Motion Signal Processing ™ Enables… Shock & Vibration Sensing

Power tool safety: Shock detection

Contact sports & industrial machinery: impact detection

White goods: vibration monitoring Predictive maintenance:

Vibration monitoring

http://www.whirlpool.com/Laundry+Gallery/Washers/prodk/src__WASHERS--cat__115--prod__1785


54

Rotation

55

ADI’s Motion Signal Processing ™ Enables… Rotation Sensing

Platform/antenna stabilization: Industrial, maritime, avionics, communications

Digital camera OIS Automotive Rollover

Detection

Measuring complex motion:

56

Inertial Measurement Unit

57

ADI’s Motion Signal Processing ™ Enables… Complex Motion Sensing

Platform Stabilization Guidance and trajectory: Mil/Aero

Detection of Motion in Free Space

Precision agriculture

Measuring motion

58

ADI’s Inertial MEMS Sensors:

Accelerometers measure linear motion

Gyroscopes measure rotation

59

ADI MEMS SENSORS: A brief history…

60

MEMS at ADI: In the beginning…

Concept began in ~1986 Market: airbag sensors

A little history…

The first airbags used ball-in-tube sensors.


MEMS at ADI: In the beginning…


1989 Demonstrated first working MEMS accelerometer

1991 First product samples

ADXL50: ADI’s First MEMS Device

65

How Do Accelerometers Work?

Strong

M a s s

Weak

M a s s

No Deceleration

M a s s

How Do Accelerometers Work?

constant

67

How Do MEMS Accelerometers Work?

Single axis accelerometer in silicon has the same components Left / Right (X-axis)

X Left Right M a s s

Proof Mass Suspension Spring

Suspension Spring

Motion

(ca. 1992-1995)

How Do iMEMS Accelerometers Work?

Single axis accelerometer in silicon has the same components Left/right (x-axis)

68

(ca. 1992-1995)

How Do iMEMS Accelerometers Work?

All moving parts are suspended above the substrate Sacrificial layer removed from below moving parts during fabrication

69

(ca. 1992-1995)

70

How Do MEMS Accelerometers Work?

Measurement of deflection is done with variable differential capacitor "finger sets"

(ca. 1992-1995)

Measuring the Position of the Proof Mass

SuspensionSpring

SuspensionSpring

SuspensionSpring

SuspensionSpring

Finger SetsFinger Sets Finger SetsFinger Sets

ProofMass

SuspensionSpring

SuspensionSpring

SuspensionSpring

SuspensionSpring

SuspensionSpring

SuspensionSpring

SuspensionSpring

SuspensionSpring

Finger SetsFinger Sets Finger SetsFinger SetsFinger SetsFinger Sets Finger SetsFinger Sets

ProofMassProofMass

X

Y

Differential capacitance used to pick off motion of mass C1 and C2 is the capacitance between the mass and a set of

fixed fingers Keep monitoring (C1 – C2) to determine if the mass has

moved in the X-axis

C1 C2

Simplified Reader Architecture

CMOS sensor clocks

sensor AC

(clock domain) Gain

demodulator DC

(baseband) Gain

convert back to baseband

amplify amplify excite

What accelerometers measure:

73

Measuring Tilt

A = G sinΦ

Acceleration due to tilt is the projection onto the sensitive axis of the gravity vector.

Φ Φ

G

Sensitive axis

G 17mg / ° tilt near level

m k

High Performance Accelerometers Industry’s Strongest and Most Complete Portfolio

Low-g

High-g

ADXL103

ADXL203

ADXL78

ADXL213

ADXL278

1

2

2

1

2 Two-Pole Bessel Filter

PWM Output

±1.7g

±1.7g

±1.7g

ADXL337 3

±3g

±35/50/70g

±35/50/70g

±70/250/500g

ADXL001 1

20-22KHz Bandwidth

ADIS16006 2

±5g 200 μg/√Hz rms SPI Temp Sensor

ADIS16003 2

±1.7g 110 μg/√Hz rms SPI Temp Sensor

0.1° accuracy Temperature Calibration Programmable/Alarms/Filtering

ADIS16209/3/1 2

±90, ±180g ADIS16227/3

3

±70g ADIS16204

2

Programmable Capture Buffers Peak Sample/Hold

±37/70g Function Specific

TILT / INCLINOMETER

Embedded FFT/Storage Programmable Alarm Bands MultiMode Operation

VIBRATION

ADXL326 ±16g

IMPACT

ADIS16240 3

±19g Programmable Triggers Event Capture Buffers

ADXL312 3

AECQ-100 Qualified

±1.5/3/6/12g

Up to 13bit resolution 30μA to 140μA power

3

IMPACT

iMEMs XL ANALOG

iMEMs XL DIGITAL

iSensor XL Digital

g

axes

axes

g

axes

g

ADXL206 2

±5g +175°C Operation

ADXL212 2

±5g

ADXL343 3

±2/4/8/16g ADXL344

3

±2/4/8/16g

ADXL345 3

±2/4/8/16g ADXL346

3

±2/4/8/16g

ADXL362 3

±2/4/8g

12bit resolution @ ±2g <2uA power consumption

ADXL377 3

±200g

ADXL350 3

Min/Max Temp Sensitivity

±1/2/4/8g

Focusing on High Performance with: • Industry Lowest Power Consumption • Industry Best Precision Over Lifetime • Industry Best Temperature Range • Industry Best Sensor/Signal Processing • Industry Best Integration … Performance Under All Conditions

Highlight Product: ADXL362: Industry’s Lowest Power MEMS Accel By far…

< 2 µA at 100 Hz in Measurement Mode 270 nA in Wake-Up Mode

Also helps save system power Enables Autonomous, Continuously Operational Motion-activated Switch Enhanced Activity/Inactivity Detection Deep FIFO

ADI’s Inertial MEMS Sensors:

Accelerometers measure linear motion

Gyroscopes measure rotation

77

Gyro Building Blocks What does one need?

x

x

x

x

A Good XL

(We already know how to do that)

+

A gizmo that converts any rotation to a force

+

A coupling mechanism that transfers the force generated by the “gizmo” to the accelerometer

Gyro Building Blocks The Coriolis Effect: Converting rotation to force since 1835

MASS

ROTATION

OSCILLATION

CORIOLIS

FORCE

What is the Coriolis effect? In plain English… a moving mass, when rotated, imparts a force to resist change in direction of motion

Gyro Building Blocks

x

x

x

x

A Good XL

(We already know how to do that)

+ + A coupling mechanism that transfers the force generated by the “gizmo” to the accelerometer

Mass with velocity

Gyro Building Blocks

x

x

x

x

Coupling mechanism:

Cut a hole in the middle of XL and drop the “moving mass” inside

Mass with velocity

RESONATOR MOTION

Gyro Principle of Operation

82

ACCELEROMETER TETHER RESONATOR TETHER

ACCELEROMETER FRAME

RESONATOR

CO

RIO

LIS A

CC

ELE

RATIO

N

APPLIED ROTATION

ANCHOR


83

No Rotation


84

Rotation Applied

How Do Gyros Work?

Video showing motion of proof mass

85

Problems with Single Mass Gyros

Single mass gyros generally cannot differentiate between rotation (which you want to measure) and vibration at the resonant frequency

86


87

Rotation Applied

-

+

ADXRS series design use two beams (masses) resonating in anti-phase (180° out of phase) Shock and vibration is common mode, so differential operation allows rejection

of many errors


88

Vibration Applied

-

+

Cancelled out

Photograph of Mechanical Sensor

89

Problems With Single Mass Gyros…

…are also problems with dual-mass gyros, just to a lesser extent.

That wasn’t good enough for us.

The Latest

High Performance Gyro and IMU Industry’s Strongest and Most Complete Portfolio

Rate Grade

Tactical Grade

> 10 o/hr in-run Stability

< 10 o/hr in-run Stability

ADXRS45X

ADIS16265

ADXRS646

ADXRS642

0.015o/s/g 5mA

6 o/hr 16ppm/oC Sensitivity

ADIS1636X / 405/7

ADIS16305

6, 9, 10

4

ADIS16375 6

ADIS16334 6

ADIS16385 6

12o/hr; 0.13mg Stability 0.013o/s/g Continuous Bias Estimation

<8cm3 40ppm/oC

ADIS16135/3

6o/hr, Yaw

Quad-Core Designs Industry Leading Vibration

Immunity

ADXRS62x/ 652

Vertical Mount Package option

25ppm/oC Sensitivity

iMEMs Gyro ANALOG

iMEMs Gyro DIGITAL

iSensor Gyro Digital

IMU (DoF)-X

0.03o/s/g

ADIS16488

ADIS16448

in development

0.015o/s/g 1000o/sec range 40ppm/oC 8cm3

6 o/hr ; 0.1mg 0.009o/s/g

6 - 10

6 - 10

Up to 1200o/sec

ADIS16136 4 o/hr 0.18 ARW

goals

ADIS-NxGn ADXRS-NxGn

Highlight Product: ADXRS64x High Performance Gyroscope Series Quad differential sensor technology

Pin and package compatible to ADXRS62x family

Superb vibration rejection Sensitivity to Linear Acceleration as low as 0.015°/s/g Vibration Rectification as low as 0.0001°/s/g2

Various flavors: Bias stability as low as 12°/hour Rate noise density as low as 0.01°/s/√Hz Angular measurement range up to 50,000°/s Startup time as fast as 3 msec

Power consumption down to 3.5 mA

ADXRS64x Gyros Feature ADI’s Unique Quad Differential

Sensor Design

MEMS Microphone

94

Just another accelerometer in disguise

Microphone Technology Trends to MEMS Performance is unaffected by Pb-

free solder reflow temperature

Replaces high cost manual sorting and assembly with automated assembly

Higher SNR and superior matching

Higher mechanical shock resistance

Wider operating temperature range

Consumes less current

Superior performance part-to-part, overtemperature, and with vibration

95

MEMS

DIGITAL OUTPUT

MEMS

ANALOG OUTPUT

ECM

JFET

ADI Microphone Structure

Diaphragm and back plate electrodes form a capacitor

Sound pressure causes the diaphragm to vibrate and change the capacitance

Capacitance change is amplified and converted to analog or digital output

DIAPHRAGM

PERFORATED BACK PLATE

SPRING SUSPENSION SENSE GAP

Normal conversation: 60 dB (or 20 MPa) 0.55 nm (5.5 A)

Crying baby: 110 dB 170 nm (1700 A)

How Much Does ADI MEMS Microphone Diaphragm Move?

97

Why Use MEMS Microphones? Performance Density Electret mics performance degrades quickly in smaller packages

MEMS mics achieve new level of performance in the same volume as the smallest electrets!

98

70dB

55dB

Microphone Physical Volume (cubic millimeters)

10mm3 100 200 300 400 500 600 700

MEMS MICROPHONES

ELECTRET-BASED MICROPHONES

SNR

MEMS MICS SHIFTS THE SNR-TO-VOLUME SLOPE

UP DRAMATICALLY!

Why Use MEMS Microphones? Less Sensitivity Variation vs. Temperature ECM vs. ADMP441

99 Change (in dB) from original sensitivity

Top vs. Bottom Port: Performance Impact Bottom Port Provides Superior SNR & Frequency Response

100

All top-port microphones (MEMS and ECM) currently on the market have sharp peaks in their high-frequency response, making them unacceptable for wideband voice applications

All top-port microphones have low SNR (55…58 dB) There are no top-port microphones with high performance currently on the market

ADI Bottom-Port MEMS Microphone Competitor Top-Port MEMS Microphone

Industry’s Most Integrated MEMS Mic

ADMP441 integrates more of the signal chain than any other MEMS Mic!

Typical analog output mics (ADMP404) integrate an output amp Typical digital output mics (ADMP421) integrate an ADC and provide a single bit

output stream (known as “pulse density modulation” or PDM) – which still requires a filter and some signal processing and PDM codecs focus on mobile devices

ADMP441 provides full I2S output – the most common digital audio interface

ADMP441 ADMP421

ADMP404

Secondary Amplifier

Serializer I2S, etc.

Digital Signal Processor or

Microcontroller

Filter

ADI MEMS Microphone Portfolio High Performance MEMS Microphones

ADMP441 Full I2S-Output

Most integrated microphone

available!

ADMP421 61dB SNR

Pulse Density Modulated (PDM)

Output

Digital Output Higher Integration

Package

3.35x2.6x0.88 mm

4.72x3.76x1 mm

4x3x1 mm

Analog Output Flexibility in Signal Acquisition

ADMP405 62dB SNR

200 Hz to 15 kHz Flat Frequency Response

ADMP401 100 Hz to 15 kHz Flat Frequency Response

ADMP521 65dB SNR

Pulse Density Modulated (PDM)

Output

ADMP404 62dB SNR

100 Hz to 15 kHz Flat Frequency Response

ADMP504 65dB SNR

100 Hz to 15kHz Frequency Response

65dB SNR Family

62dB SNR Family


What We Covered

Sensors are the source

Sensor signals are typically low-level and difficult

Signal conditioning is key to high performance

Silicon sensors are integrated with signal conditioning

Applications keep demanding higher accuracy

Motion sensors with moving silicon elements are driving systems in all market areas

103


Design Resources Covered in this Session

Design Tools and Resources:

Ask technical questions and exchange ideas online in our EngineerZone ® Support Community Choose a technology area from the homepage: ez.analog.com

Access the Design Conference community here: www.analog.com/DC13community

104

Name Description URL

Photodiode Wizard Photodiode/amplifier design tool

http://ez.analog.com/welcome

http://www.analog.com/DC13community


Selection Table of Products Covered Today

105

Part number Description AD590/592/TMP17 Two-terminal current-out temperature sensor AD849x Thermocouple amplifier w/cold junction compensation ADT7320/7420 0.25C accurate digital temperature sensors AD7793 24-bit ADC with RTD sensor driver ADA4638 Photodiode amplifier ADXL362 2µA high-resolution digital accelerometer ADXRS64X High performance gyroscope series ADMP404/504 High performance analog microphones ADMP441 Complete digital microphone w/ filter


Visit the K-Type Thermocouple Measurement System with Integrated Cold-Junction Compensation (CN0271) in the Exhibition Room

This is a complete thermocouple measurement system with cold junction compensation for Type K. It includes a 16-bit Ʃ-∆ ADC, cold-junction amplifier, and low noise instrumentation amplifier to provide common-mode rejection for long lines.

106

Image of demo/board

This demo board is available for purchase: http://www.analog.com/DC13-hardware

http://www.analog.com/DC13-hardware


Visit the Tilt Measurement Demo in the Exhibition Room

107

Measure tilt using the ADXL203 dual axis accelerometer

This demo board is available for purchase: www.analog.com/DC13-hardware

SDP-S BOARD SOFTWARE OUTPUT DISPLAY EVAL-CN0189-SDPZ

http://www.analog.com/DC13hardware

Sensors for Low Level Signal Acquisition (Design Conference 2013)

Technology

Transcript of Sensors for Low Level Signal Acquisition (Design Conference 2013)