A summary of the workshop on ¨Smart Sensors Systems 2012" that I attented at TU/Delft

1. Welcome
Specificaitons, Design & Development of smart
silicon sensor systems
Mayur Sarode
Engineer at INCAS3
Assen, The Netherlands

2. About the workshop
 Smart Sensor Systems 2012 by Delft Institute of Microelectronics (DIMES)
 Lectures , demonstrations, visit to clean room at TU/Delft.

3. Lectures
1. Silicon sensors: Applications and Future Perspectives by Paddy French, TU/Delft.
2. Designing Smart Sensors and Smart Sensor Systems by Kofi Makinwa, TU/Delft.
3. Measurement techniques for smart sensor systems by Gerard Meijer, TU/Delft.
4. Calibration and Self-Calibration of Smart Sensors by Michiel A.P Pertijs, TU/Delft.
5. Integrated Hall Magnetic sensors by Pavel Keijk EPFL Lausanne, Switzerland.
6. Capacitive Sensors by Xiujin Li, TU/Delft.
7. Smart temperature sensors by Gerard Meijer, TU/Delft.
8. Optical Sensors Based on Photon Detection by Reinoud Wolffenbuttel , TU/Delft.
9. Physical chemosensors by Michel Velekoop, TU/Vienna.
10. Dynamic offset-cancellation techniques by Kofi Makinwa, TU/Delft.
11. Precision Instrumentation Amplifiers by Johan Huijsing , TU/Delft.
12. Universal asynchronous sensor interfaces by Gerard Meijer, TU/Delft.
13. Implantable Smart Sensors for Advanced Medical Devices by Tim Dension, Medtronics
14. Interface electronics and A/D converters by Frank Reidijk, Xensor Integrartion
15. Introduction to CMOS-based DNA Microarrays by Jan Bosiersm Dalasa
16. Energy harvesting Sensor Systems by Ruud Vullers

4. What are Smart sensors?
Sensors ~“Smart sensor”
o Low cost, Small size, Multi-sensing
o Self-test, digital output, bus interface, RF, energy scavening
Transducers ~ self generating, modulating
MEMS + CMOS design ~ a smart sensor

5. Silicon Sensors
MEMS sensors~good planar processing technology
Silicon not the best in class!
Package design & analog design
Signal processing to compensate for silicon defects
Radiant
Photo diodes
(CMOS image sensors, optical sensors)
Chemical Thermal
Resistors, transistors,
ISFETS
thermopiles
DNA detector, chemeosensors
(temperature, wind sensor)
Electrical
Resistors,capaci
Mechanical tors, inductors, Magnetic
Diaphram, (Capacitive Hall-plates, magFET’s, coil
(micromachiened devices) (Hall sensors)
sensors)

6. Silicon Sensors
Radition Domain
• P-N junction depletion layer
• Shorter wavelentgth is absorbed by silicon
• CCD’s, position sensors
 Mechanical Domain
• can introduce self test
• Pressure and accelerartion sensors
Thermal domain
• Silicon sensitive to temperature
• Temperature and flow measurement
Magnetic Domain
• Based on Hall effect
• Magnetic field measurement, current, rotation and position
 Chemical Domain
• Physical chemeosensors

7. Smart Sensor Systems: System specs.
 On Silicon
 Output format
 Sensor bandwidth ~ 10 KHz
 Errors: offset, drift, noise, cross sensitivity, linearity, impedance, multipath
 Measurement techniques to solve these problems
• nested chopping
•Dynamic element matching
•Auto calibration

8. Smart Sensor Systems: functionality
 Hardware
General hybrid solution
Sensing Signal A/D Bus Processor
element Conditioning converter Intefacing
Universal transducer interface
One chip solution
 Software
Data
oSelf test in accelerometer Self testing
evaluation
Auto-Calibration
oTransducer electronic data sheet (TEDS)
oThree signal measurement Auto-
identificaiton
calibration

9. Reducing errors
• Random, Systematic, multi-path error
• Auto zeroing vs Chopping
• Reduces 1/f noise , offset,

10. Autocalibration
 What is Mx ??
100 Kg Mx Kg
5 Kg 55 Kg 25 Kg
 High accuracy ~high dynamic range
Sense1
Rotating
Resistors
Sense2

11. Compensating for parasitic effects
 Cable and wire impedance
Zs1 Zs3 YX
Vforce Isense
Yp1
Iforce Vsense
Yp2
ZX
Zs2 Zs4
Low ohmic impedance ( current) High ohmic impedance ( voltage)
Cross and parasitic effects
Zp
Cx Rp
Rx Cp Yp
Ix
Vx
Capacitve sensors resistive sensors
Votlage generating sensors Current generating sensors
(humdity sensors) (thermistors/photoresistors)
(thermopiles/PH) (photo detectors)
Use of additonal sensors
Excitation signal, DC vs square vs sinusoidal vs pulsed, frequency

12. Smart sensor Systems: A/D converters
Conventional system
Analog Off the shelf
Front processor
A/D
end converter
Smart A/D conversion
Period
converter Tsense Treference Toffset
Sensing element processor
reference element MUX
Offset element
MUX S/H circuit
capacitve control Quantization
Digital filtering
ΣΔ converter
•Also used with resistive sensors

13. Universal Sensor Interface
System Setup
Sensing, signal conditioning , A/D conversion
Universal interface for interfacing sensor element to the processor

14. Smart sensor systems design
Wind sensor design at TU/Delft
System design~ sensor biasing
Digitize early, modulation techniques for silicon
limitations
Characteristics
oSlow, use dynamic techniques
oSmall output voltage, spreads, thermal balancing
oThermal offset due to placement
Auto-zeroing of comparator~ low thermopile output
1.6 μm technology
10 bit ΣΔ ADC .

15. Smart temperature Sensors
 Absolute temp sensors
Thermistors( cheap, non linear, sensitive,
-80 to 200 ºC
Platinum resistors (expensive, stable, -260 to 1000 ºC)
Thermocouple (reference junction and measurement
Junctions
Microcontroller
Silicon Vbe ~ temperature
 On silicon chips
Integrated thermistors
1.Comparable to Pt resistors Sensor
Interface
2.Stress dependent
3.Voltage dependent non linear behaviour
Thermocouples
1.No offset, no calibration
Measuring absolute temperature. Smart Temperature
Temperature Sensing
Sensor elements

16. Smart tempearature Sensors
Design considerations
 Accuracy
Triple point of water ~ defined fixed point
Absolute accuracy vs drift
 Drift (1 mK ~ 10 mK)
Cross sensitivity to mechanical stress accuracy noise and
resolution
Reduced to 100 mK with packaging
 Self heating
Dynamic behaviour
Thermal design considerations
Long term stability

17. So how to design it?
 Problem statement
Microrganism detection in milk products.
System level design
Circuit level design
DC DC
Im Is
Milk carton Milk carton
Sensor

18. Conclusions

19. Thank you