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The World Leader in High Performance Signal Processing SolutionsFUNDAMENTALS OF DESIGN         Class 1      Introduction  ...
The Goal Capture what is going on in the real world Convert into a useful electronic format Analyze, Manipulate, Store,...
The real world is NOT digital
Analog to Electronic signal processing           Sensor      Amp   Converter    Digital Processor           (INPUT)       ...
The SensorAnalog, but                Analog              Sensor    NOT       (INPUT)        AND                           ...
Popular sensors                  Sensor Type      Output              Thermocouple         Voltage                  Photod...
Thermocouple Very  low level (µV/ºC) Non-linear Difficult to handle Wires need insulation Susceptible to noise Fragile
Sensor Signal Conditioning Sensor                        Amp             Analog,                                Analog,   ...
Types of Temperature Sensors    THERMOCOUPLE               RTD          THERMISTOR         SEMICONDUCTOR     Widest Range:...
Common Thermocouples                               TYPICAL        NOMINAL         ANSI    JUNCTION MATERIALS         USEFU...
Thermocouple Output Voltagesfor Type J, K and S Thermocouples      THERMOCOUPLE OUTPUT VOLTAGE (mV)   60                  ...
Thermocouple Seebeck Coefficient vs.Temperature                                     70                                    ...
Thermocouple Basics      A. THERMOELECTRIC VOLTAGE                C. THERMOCOUPLE MEASUREMENT                             ...
Using a Temperature Sensor for Cold-Junction Compensations                            V(OUT)                        TEMPER...
AD594/AD595 Monolithic ThermocoupleAmplifier with Cold-Junction Compensation                                           +5V...
Basic Relationships For SemiconductorTemperature Sensors                       IC                              IC         ...
Classic Bandgap Temperature Sensor                 +VIN                              R                       R          "B...
Analog Temperature Sensors  Product   Accuracy   Max Accuracy     Operating        Supply        Max      Interface       ...
Digital Temperature SensorsComprehensive Portfolio of Accuracy Options          Product   Accuracy (Max)     Max Accuracy ...
Position and Motion Sensors Linear   Position: Linear Variable Differential Transformers  (LVDT) Hall Effect Sensors   ...
+     THREADED       CORE                                 VA                       ~                         VOUT = VA – V...
AD698EXCITATION              AMP       ~       REFERENCE                              OSCILLATOR                    B     ...
Hall Effect Sensors    T                  CONDUCTOR                           OR                     SEMICONDUCTORI       ...
AD22151 Linear Output MagneticField Sensor V / 2       V = +5V                                 CC                         ...
Accelerometer Applications Tilt or Inclination   Car Alarms   Patient Monitors   Cell phones   Video games Inertial ...
ADXL-family Micro-machined  Accelerometers AT REST               CS1      CS2   APPLIED ACCELERATIONCENTER PLATE         T...
Using an Accelerometer to Measure Tilt                              +90°       X                   X                      ...
Gyro Axes of Rotational Sensitivity
Coriolis acceleration example.
Displacement due to the Coriolis Effect
Photograph of mechanical sensor.
High Impedance Sensors Photodiodes Piezoelectric   Sensors  Accelerometers  Hydrophones Humidity   Monitors pH   Mon...
Photodiode Equivalent CircuitINCIDENT  LIGHT                  PHOTO    RSH(T)                 CURRENT             CJ   IDE...
Current-to-voltage Converter (Simplified)                         R = 1000M       ISC = 30pA        (0.001 fc)           ...
Preamplifier DC Offset Errors                          1000M   R2                         IB                   ~         ...
Sensor Resistances Used In BridgeCircuits Span A Wide Dynamic Range   Strain Gages                            120, 350,...
Wheatstone Bridge Produces An Output NullWhen The Ratios Of Sidearm Resistances Match                          VB         ...
Output Voltage Sensitivity And Linearity Of Constant Current DriveBridge Configurations Differs According To The Number Of...
A Generally Preferred Method Of Bridge Amplification EmploysAn Instrumentation Amplifier For Stable Gain And High CMR     ...
Upcoming webcasts Converter     Simulation: Beyond the Eval Board    January 19th at 3:00 p.m. (ET) RF   Detectors    ...
Fundamentals Webcasts 2011 January  Introduction and Fundamentals of Sensors February The Op Amp March Beyond the Op Am...
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Fundamentals of Designing with Sensors

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Sensors help to capture what is going on in the real world. This deck explains how real-world information, such as pressure, temperature, speed is converted into a useful electronics format that can be analyzed, manipulated, stored or sent to another device.

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Fundamentals of Designing with Sensors

  1. 1. The World Leader in High Performance Signal Processing SolutionsFUNDAMENTALS OF DESIGN Class 1 Introduction Presented by David Kress
  2. 2. 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
  3. 3. The real world is NOT digital
  4. 4. Analog to Electronic signal processing Sensor Amp Converter Digital Processor (INPUT) Actuator Amp Converter (OUTPUT)
  5. 5. The SensorAnalog, but Analog Sensor NOT (INPUT) AND Amp Converter Digital Processor electronic electronic Actuator Amp Converter (OUTPUT)
  6. 6. Popular sensors Sensor Type Output Thermocouple Voltage Photodiode Current Strain Gauge Resistance Microphone Capacitance Touch Button Charge Output Antenna Inductance
  7. 7. Thermocouple Very low level (µV/ºC) Non-linear Difficult to handle Wires need insulation Susceptible to noise Fragile
  8. 8. Sensor Signal Conditioning Sensor Amp Analog, Analog, electronic, electronic, but “dirty” and “clean” •Amplify the signal to a noise-resistant level •Lower the source impedance •Linearize (sometimes but not always) •Filter •Protect
  9. 9. Types of Temperature Sensors THERMOCOUPLE RTD THERMISTOR SEMICONDUCTOR Widest Range: Range: Range: Range: –184ºC to +2300ºC –200ºC to +850ºC 0ºC to +100ºC –55ºC to +150ºC High Accuracy and Fair Linearity Poor Linearity Linearity: 1ºC Repeatability Accuracy: 1ºC Needs Cold Junction Requires Requires Requires Excitation Compensation Excitation Excitation Low-Voltage Output Low Cost High Sensitivity 10mV/K, 20mV/K, or 1µA/K Typical Output
  10. 10. Common Thermocouples TYPICAL NOMINAL ANSI JUNCTION MATERIALS USEFUL SENSITIVITY DESIGNATION RANGE (ºC) (µV/ºC) Platinum (6%)/ Rhodium- 38 to 1800 7.7 B Platinum (30%)/Rhodium Tungsten (5%)/Rhenium - 0 to 2300 16 C Tungsten (26%)/Rhenium Chromel - Constantan 0 to 982 76 E Iron - Constantan 0 to 760 55 J Chromel - Alumel –184 to 1260 39 K Platinum (13%)/Rhodium- 0 to 1593 11.7 R Platinum Platinum (10%)/Rhodium- 0 to 1538 10.4 S Platinum Copper-Constantan –184 to 400 45 T
  11. 11. Thermocouple Output Voltagesfor Type J, K and S Thermocouples THERMOCOUPLE OUTPUT VOLTAGE (mV) 60 50 TYPE K 40 TYPE J 30 20 TYPE S 10 0 -10 -250 0 250 500 750 1000 1250 1500 1750 TEMPERATURE (°C)
  12. 12. Thermocouple Seebeck Coefficient vs.Temperature 70 60 TYPE J SEEBECK COEFFICIENT - µV/ °C 50 TYPE K 40 30 20 TYPE S 10 0 -250 0 250 500 750 1000 1250 1500 1750 TEMPERATURE (°C)
  13. 13. Thermocouple Basics A. THERMOELECTRIC VOLTAGE C. THERMOCOUPLE MEASUREMENT Metal A Metal A V1 – V2 Metal AV1 T1 Thermoelectric V1 T1 T2 V2 EMF Metal B Metal B B. THERMOCOUPLE D. THERMOCOUPLE MEASUREMENT Copper Copper Metal A R Metal A V Metal A Metal A I T3 T4V1 T1 T2 V2 V1 T1 T2 V2 Metal B Metal B R = Total Circuit Resistance I = (V1 – V2) / R V = V1 – V2, If T3 = T4
  14. 14. Using a Temperature Sensor for Cold-Junction Compensations V(OUT) TEMPERATURE V(COMP) COMPENSATION CIRCUIT COPPER COPPER METAL A SAME METAL A TEMP TEMP SENSOR T1 V(T1) V(T2) T2 METAL B V(COMP) = f(T2) ISOTHERMAL BLOCK V(OUT) = V(T1) – V(T2) + V(COMP) IF V(COMP) = V(T2) – V(0°C), THEN V(OUT) = V(T1) – V(0°C)
  15. 15. AD594/AD595 Monolithic ThermocoupleAmplifier with Cold-Junction Compensation +5V 0.1µF BROKEN 4.7k THERMOCOUPLE VOUT ALARM 10mV/°C OVERLOAD TYPE J: AD594 DETECT TYPE K: AD595 THERMOCOUPLE AD594/AD595 +A – – –TC ICE G + G POINT + + COMP +TC
  16. 16. Basic Relationships For SemiconductorTemperature Sensors IC IC N TRANSISTORS ONE TRANSISTOR VBE VN kT  IC  kT  IC  VBE  ln  VN  ln  q  IS  q  N  IS  kT VBE  VBE  VN  ln(N) q INDEPENDENT OF IC, IS
  17. 17. Classic Bandgap Temperature Sensor +VIN R R "BROKAW CELL" + VBANDGAP = 1.205V I2 @ I1 Q2 Q1 NA A VN VBE kTVBE  VBE  VN  ln(N) R2 (Q1) q R1 kT VPTAT = 2 ln(N) R2 q R1
  18. 18. Analog Temperature Sensors Product Accuracy Max Accuracy Operating Supply Max Interface Package (Max) Range Temp Range Current Range ± 0.5°C 25°C -55°C to TO-52,2-ld FP, AD590 4 to 30V 298uA Current Out ± 1.0°C -25°C to 105°C 150°C SOIC, Die ± 0.5°C 25°C -25°C to 298uA AD592 4 to 30V Current Out TO-92 ± 1.0°C -55°C to 150°C 105°C 0°C to 85°C -55°C to TO-92, SOT23, TMP35 ± 2.0°C 2.7 to 5.5V 50uA Voltage Out -25°C to 100°C 150°C SOIC TO-92, SOT23, -40°C to 125°C -55°C to 50uA TMP36 ± 3.0°C 2.7V to 5.5V Voltage Out SOIC 150°C ± 2.0°C -50°C to 150°C -50°C to AD22100 4 to 6.5V 650uA Voltage Out TO-92, SOIC, Die 150°C ± 2.5°C 0°C to 100°C 0°C to 100°C AD22103 2.7 to 3.6V 600uA Voltage Out TO-92, SOIC
  19. 19. Digital Temperature SensorsComprehensive Portfolio of Accuracy Options Product Accuracy (Max) Max Accuracy Interface Package Range ± 0.2°C -10°C to 85°C ADT7420/7320 I2C/SPI LFCSP ± 0.25°C -20°C to 105°C ADT7410/7310 ± 0.5°C -40°C to 105°C I2C/SPI SOIC ± 1°C (B grade) 0°C to 85°C ADT75 I2C MSOP, SOIC ± 2°C (A grade) -25°C to 100°C ± 1°C 0°C to 70°C ADT7301 SPI SOT23, MSOP ± 1°C 0°C to 70°C TMP05/6 PWM SC70, SOT23 ± 1.5°C -40°C to 70°C AD7414/5 I2C SOT23,MSOP ADT7302 ± 2°C 0°C to 70°C SPI SOT23,MSOP ± 4°C TMP03/4 -20°C to 100°C PWM TO-92,SOIC,TSSOP21
  20. 20. 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  Inductosyns (Linear and Rotational Position)  Motor Control Applications Acceleration and Tilt: Accelerometers Gyroscopes
  21. 21. + THREADED CORE VA ~ VOUT = VA – VB AC SOURCE VB 1.75" _ VOUT VOUTSCHAEVITZ _ POSITION + _ POSITION + E100 LVDT – Linear Variable Differential Transformer
  22. 22. AD698EXCITATION AMP ~ REFERENCE OSCILLATOR B VB + A VOUT FILTER AMP B A VA A, B = ABSOLUTE VALUE + FILTER _ 4-WIRE LVDT AD698 LVDT Signal Conditioner
  23. 23. Hall Effect Sensors T CONDUCTOR OR SEMICONDUCTORI I VH I = CURRENT B B = MAGNETIC FIELD T = THICKNESS VH = HALL VOLTAGE
  24. 24. AD22151 Linear Output MagneticField Sensor V / 2 V = +5V CC CC VCC / 2 R2 + R1 TEMP REF _ R3 _ AD22151 VOUT + OUTPUT AMP CHOPPER AMP VOUT = 1 + R3 0.4mV Gauss NONLINEARITY = 0.1% FS R2
  25. 25. Accelerometer Applications Tilt or Inclination  Car Alarms  Patient Monitors  Cell phones  Video games Inertial Forces  Laptop Computer Disc Drive Protection  Airbag Crash Sensors  Car Navigation systems  Elevator Controls Shock or Vibration  Machine Monitoring  Control of Shaker Tables ADI Accelerometer Fullscale g-Range: ± 2g to ± 100g ADI Accelerometer Frequency Range: DC to 10kHz
  26. 26. ADXL-family Micro-machined Accelerometers AT REST CS1 CS2 APPLIED ACCELERATIONCENTER PLATE TETHER BEAM CS1 CS1 = CS2 < CS2 FIXED OUTER PLATES DENOTES ANCHOR
  27. 27. Using an Accelerometer to Measure Tilt +90° X X 1g  Acceleration 0° –90° +1g Acceleration = 1g × sin  0g  –90° 0° +90° –1g
  28. 28. Gyro Axes of Rotational Sensitivity
  29. 29. Coriolis acceleration example.
  30. 30. Displacement due to the Coriolis Effect
  31. 31. Photograph of mechanical sensor.
  32. 32. High Impedance Sensors Photodiodes Piezoelectric Sensors  Accelerometers  Hydrophones Humidity Monitors pH Monitors Chemical Sensors Smoke Detectors Charge Coupled Devices and Contact Image Sensors for Imaging
  33. 33. Photodiode Equivalent CircuitINCIDENT LIGHT PHOTO RSH(T) CURRENT CJ IDEAL DIODE 100k - 100G NOTE: RSH HALVES EVERY 10 C TEMPERATURE RISE
  34. 34. Current-to-voltage Converter (Simplified) R = 1000M ISC = 30pA (0.001 fc) _ VOUT = 30mV + Sensitivity: 1mV / pA
  35. 35. Preamplifier DC Offset Errors 1000M R2 IB ~ _ OFFSET VOS RTO R1 IB + R3 DC NOISE GAIN = 1 + R2 R1 IB DOUBLES EVERY 10 C TEMPERATURE RISE R1 = 1000M @ 25 C (DIODE SHUNT RESISTANCE) R1 HALVES EVERY 10 C TEMPERATURE RISE R3 CANCELLATION RESISTOR NOT EFFECTIVE
  36. 36. Sensor Resistances Used In BridgeCircuits Span A Wide Dynamic Range  Strain Gages 120, 350, 3500  Weigh-Scale Load Cells 350 - 3500  Pressure Sensors 350 - 3500  Relative Humidity 100k - 10M  Resistance Temperature Devices (RTDs) 100 , 1000  Thermistors 100 - 10M
  37. 37. Wheatstone Bridge Produces An Output NullWhen The Ratios Of Sidearm Resistances Match VB THE WHEATSTONE BRIDGE: R4 R3  R1 R2  VO  VB     R1 + R4 R2 + R3  VO AT BALANCE, R1 R2 VO = 0 if  R4 R3 R1 R2
  38. 38. Output Voltage Sensitivity And Linearity Of Constant Current DriveBridge Configurations Differs According To The Number Of ActiveElements IB IB IB IB R R R+R R R RR R+R RR VO VO VO VO R R+R R R+R R R+R RR R+R R VO: IBR R IB R IB R IB R 4 R + 2 2 4Linearity 0.25%/% 0 0 0Error: (A) Single-Element (B) Two-Element (C) Two-Element (D) All-Element Varying Varying (1) Varying (2) Varying
  39. 39. A Generally Preferred Method Of Bridge Amplification EmploysAn Instrumentation Amplifier For Stable Gain And High CMR VB OPTIONAL RATIOMETRIC OUTPUT VREF = VB +VS R R R  VB VOUT = R GAIN 4 R + RG 2 IN AMP REF VOUT + R R+R -VS* * SEE TEXT REGARDING SINGLE-SUPPLY OPERATION
  40. 40. Upcoming webcasts Converter Simulation: Beyond the Eval Board  January 19th at 3:00 p.m. (ET) RF Detectors  February 16th at Noon (ET) Challenges in Embedded Design for real-time systems  March 16th at Noon (ET) www.analog.com/webcast
  41. 41. Fundamentals Webcasts 2011 January Introduction and Fundamentals of Sensors February The Op Amp March Beyond the Op Amp April Converters, Part 1, Understanding Sampled Data Systems May Converters, Part 2, Digital-to-Analog Converters June Converters, Part 3, Analog-to-Digital Converters July Powering your circuit August RF: Making your circuit mobile September Fundamentals of DSP/Embedded System design October Challenges in Industrial Design November Tips and Tricks for laying out your PC board December Final Exam, Ask Analog Devices www.analog.com/webcast

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