Transcript Document

Smart Sensor Interface
Electronics
October 7th, 2005
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Contents
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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
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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
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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
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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
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Parasitic effects in the sensing element
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Sensor elements will usually have certain
parasitic electrical effects
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Parasitic effect in sensing
elements
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The effect cable and wire impedance
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Avoid impedance of connecting wires and
cables affecting the measurement
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Analog-to-digital conversion
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Conventional systems
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Uses off-the-shelf A/D converter
More complicated analog front end
Smart sensor systems
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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
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Systematic errors
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Filtering
Separation of common-mode and
differential-mode signals
Proper design
Random errors
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Calibration
Sensor-under-test
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High accuracy over a wide
dynamic range
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Advanced chopping techniques
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Chopping can be applied to reduce random
errors also
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High accuracy over a wide
dynamic range
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Autocalibration
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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
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Dynamic amplification and division
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High accuracy over a wide
dynamic range
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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
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