Smart Sensor Interface Electronics

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Smart Sensor Interface Electronics

• October 7th, 2005

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Contents

• Introduction
• Object-oriented design of sensor systems
• Parasitic effect in sensing elements
• Analog-to-digital conversion
• High accuracy over a wide dynamic range
• A universal sensor interface
• A wide range voltage processor

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Introduction

• Information processing systems need sensors to
  acquire physical and chemical information
• Cost reduction needed for systems with many
  sensors
• Can be achieved by using smart sensors

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Object-oriented design of sensor systems

• Cost is reduced and performance is improved by
  merging and re-evaluating the functions of the
  sensors
• Implementation on common substates or on single
  chips

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Object-oriented design of sensor systems
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Parasitic effect in sensing elements

• Excitation signals for sensing elements
• Square-wave excitation signal preferred
• Signal should be as large as possible
• Avoid undesired electo-physical interaction

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Parasitic effect in sensing elements

• Parasitic effects in the sensing element
• Sensor elements will usually have certain
  parasitic electrical effects

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Parasitic effect in sensing elements

• The effect cable and wire impedance
• Avoid impedance of connecting wires and cables
  affecting the measurement

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Analog-to-digital conversion

• Conventional systems
• Uses off-the-shelf A/D converter
• More complicated analog front end
• Smart sensor systems
• A/D converter is merged into sub-systems

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Analog-to-digital conversion
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High accuracy over a wide dynamic range

• Systematic errors
• Filtering
• Separation of common-mode and differential-mode
  signals
• Proper design
• Random errors
• Calibration
• Sensor-under-test

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High accuracy over a wide dynamic range

• Advanced chopping techniques
• Chopping can be applied to reduce random errors
  also

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High accuracy over a wide dynamic range

• Autocalibration
• Eliminates undesirded effects of changes in the
  transfer parameters
• Two-signal or three-signal approach

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High accuracy over a wide dynamic range

• Dynamic amplification and division

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High accuracy over a wide dynamic range

• DEM Switched Capacitor amplifier

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A universal sensor interface
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A wide range voltage processor
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A wide range voltage processor