Sensors in Digital Health
Sensors in Digital Health! Matthew Guthaus! Associate Professor! UCSC, Computer Engineering! http://vlsida.soe.ucsc.edu! [email protected]!
Terminology • Embedded System! – Typically implemented on a Printed Circuit Board (PCB)! – NSF now calls it “Cyberphysical Systems”! – Includes microprocessor, memory, sensors, and actuators (more later)!
• System-on-Chip! – Integrates from PCB to single semiconductor chip! – Integrating the components decreases cost, size, and power! ! • Most expensive part of a “chip” is the package that contains the silicon and attaches to a board -> fewer chips is better.!
10/31/13!
Sensors in Digital Health
2
Pervasiveness of Sensor Systems • Automotive & Industrial! – Embedded control systems with sensor and actuator type applications.!
• Network! – Switches, routers, and firewalls that send/receive network signals.!
• Consumer! – Consumer devices like cameras, PDAs, scanners, etc.!
• Telecommunications! – Encoding and decoding communication (radio) signals.!
• Office! – Embedded office machinery like scanners, printers, etc.!
• Health! – Biometrics, activity, etc.!
10/31/13!
Sensors in Digital Health
3
Important Criteria • Power! – Battery requirements! – Communication power! – Display power!
• Size! – Implementation Technology!
• Accuracy (resolution) vs Speed! – Usually a trade-off!
• Lifetime! – Use once? Reusable?!
• Cost (economies of scale)! 10/31/13!
Sensors in Digital Health
4
Physical Principles • • • • • • •
Electric Potential, Fields, Charge! Capacitance, Resistance, Inductance! Magnetism and Hall Effect! Piezo- or Pyro-electric (deform or heat/cool)! Thermoelectric (Seebeck, Peltier effects)! Sound Waves! Temperature and Thermal (Expansion, capactiy)! • Heat Transfer (Conduction, convection, radiation)! • Light (Polarization, scattering/absorption)! 10/31/13!
Sensors in Digital Health
5
Actuators • Many systems are no longer passive, but “act” on the object under measure! – Motors! – Lights! – Relays/Switches! – Valves! – Heaters/Coolers!
• Often then have “feedback control”! – For example, anti-lock brakes!
10/31/13!
Sensors in Digital Health
6
Transducers • Often, we cannot measure a stimulus directly, so we need to convert it.! – Example 1: sound wave to mechanical (diaphram) to coil/magnetic to electric! – Example 2: speaker is just the opposite!!
Handbook of Modern Sensors
10/31/13!
Sensors in Digital Health
7
Sensors Systems! 1. 2. 3. 4. 5.
No Contact! Passive Direct! Passive Indirect! Active! Internal Sensor!
Handbook of Modern Sensors
10/31/13!
Sensors in Digital Health
8
Example: Pulse Oximeter! 1 LED (Red and Infra.)! • •
Oxy. = Red = 660nm! Non. = Infra. = >805nm!
Microcon troller
2 Calibration! • •
3 4 5 6
A2D
Thickness of finger! Pigment!
Wikipedia
Absorption! Photodetection! Analog to Digital (A2D)! Relative Comparison! Texas Instruments AFE4400
10/31/13!
Sensors in Digital Health
9
Mixed-Signal Microcontroller (MS-8) System-onChip! Timers!
Control!
Temp.! Sensor!
Bandgap! Reference!
12-bit! ΣΔ
ADC!
PGA! LPF!
Capacitive! Interface!
16-bit! Slope! ADC!
Processor Core!
Voltage!
Analog Interface!
Watchdog!
USART!
Parallel I/O!
Parallel I/O!
MAC!
CLK Manager!
Amperometric! Interface!
Prog. Mem.!
Kraver, Guthaus, et al.
10/31/13!
Sensors in Digital Health
Data Mem.!
10
MS-8 System-on-Chip Die Photo!
IMEM
Analog
Kraver, Guthaus, et al. DMEM
Core
ROM
D. Sylvester et al. 10/31/13!
Sensors in Digital Health
11
Demonstration! Time Response: each step represents a decade jump in potassium concentration
1.8 1.7 1.6 1.5 0
200
400
600
800
1000 1.9
Time (s)
Calibration Curve for Potassium Kraver, Guthaus, et al.
10/31/13!
Output Voltage (V)
Output Voltage (V)
1.9
V = 0.0525Log(C) + 1.8211! R2 = 0.9998!
1.8 1.7 1.6 1.5
-7
-6
-5
-4
-3
Concentration 10x (M) Sensors in Digital Health
-2
-1
0
12
Calibration! • Matches actual values with theoretical model! – Linear, Quadratic, Polynomial, Exponential, PWL, etc.! – Mismatch is due to! • Manufacturing tolerance! • Environment (temperature, humidity)! • Hysteresis! • Non-ideal behavior (nonlinearity, saturation, etc.)!
• Sensors have limited range of validity! Handbook of Modern Sensors
10/31/13!
Sensors in Digital Health
13
Sensor Fabrication • Organic: biological membranes, etc.! – Often better quality measurements! – Often difficult to use (aqueous solutions)!
• Inorganic: semiconductors, thin films, etc.! – Often cheaper! – Often more durable!
Source: Freescale
MEMS: Micro-Electrical Mechanical Systems Maitra, Kim, Dunbar. Recent advances in nanopore sequencing, Electrophoresis, Dec. 2012. 10/31/13!
Sensors in Digital Health
14
Hobbyist Resources • Demo Boards! – Arduino ($25)! • Shields!
– Raspberry Pi ($25)! • Operating System!
– SensorTAG ($25)! • Bluetooth/Wireless!
10/31/13!
Sensors in Digital Health
15
Mobile Platform Sensors • • • • • • • • • •
Radio/Camera! Acceleration! Ambient Light! Proximity! Gyroscope! Magnetometer! Temperature! Humidity! Pressure! Fingerprint! 10/31/13!
Sensors in Digital Health
16
What happens next? • • • •
We already have tons of data.! We are only going to get more data.! What do we do with the data?! Pervasive sensor systems to Personalized sensor systems.! – Gathering the data.! – Managing the data.! – Mining the data.! – Acting on the data.! Dexcom continuous glucose monitoring. 10/31/13!
Sensors in Digital Health
17
Terminology • Embedded System! – Typically implemented on a Printed Circuit Board (PCB)! – NSF now calls it “Cyberphysical Systems”! – Includes microprocessor, memory, sensors, and actuators (more later)!
• System-on-Chip! – Integrates from PCB to single semiconductor chip! – Integrating the components decreases cost, size, and power! ! • Most expensive part of a “chip” is the package that contains the silicon and attaches to a board -> fewer chips is better.!
10/31/13!
Sensors in Digital Health
2
Pervasiveness of Sensor Systems • Automotive & Industrial! – Embedded control systems with sensor and actuator type applications.!
• Network! – Switches, routers, and firewalls that send/receive network signals.!
• Consumer! – Consumer devices like cameras, PDAs, scanners, etc.!
• Telecommunications! – Encoding and decoding communication (radio) signals.!
• Office! – Embedded office machinery like scanners, printers, etc.!
• Health! – Biometrics, activity, etc.!
10/31/13!
Sensors in Digital Health
3
Important Criteria • Power! – Battery requirements! – Communication power! – Display power!
• Size! – Implementation Technology!
• Accuracy (resolution) vs Speed! – Usually a trade-off!
• Lifetime! – Use once? Reusable?!
• Cost (economies of scale)! 10/31/13!
Sensors in Digital Health
4
Physical Principles • • • • • • •
Electric Potential, Fields, Charge! Capacitance, Resistance, Inductance! Magnetism and Hall Effect! Piezo- or Pyro-electric (deform or heat/cool)! Thermoelectric (Seebeck, Peltier effects)! Sound Waves! Temperature and Thermal (Expansion, capactiy)! • Heat Transfer (Conduction, convection, radiation)! • Light (Polarization, scattering/absorption)! 10/31/13!
Sensors in Digital Health
5
Actuators • Many systems are no longer passive, but “act” on the object under measure! – Motors! – Lights! – Relays/Switches! – Valves! – Heaters/Coolers!
• Often then have “feedback control”! – For example, anti-lock brakes!
10/31/13!
Sensors in Digital Health
6
Transducers • Often, we cannot measure a stimulus directly, so we need to convert it.! – Example 1: sound wave to mechanical (diaphram) to coil/magnetic to electric! – Example 2: speaker is just the opposite!!
Handbook of Modern Sensors
10/31/13!
Sensors in Digital Health
7
Sensors Systems! 1. 2. 3. 4. 5.
No Contact! Passive Direct! Passive Indirect! Active! Internal Sensor!
Handbook of Modern Sensors
10/31/13!
Sensors in Digital Health
8
Example: Pulse Oximeter! 1 LED (Red and Infra.)! • •
Oxy. = Red = 660nm! Non. = Infra. = >805nm!
Microcon troller
2 Calibration! • •
3 4 5 6
A2D
Thickness of finger! Pigment!
Wikipedia
Absorption! Photodetection! Analog to Digital (A2D)! Relative Comparison! Texas Instruments AFE4400
10/31/13!
Sensors in Digital Health
9
Mixed-Signal Microcontroller (MS-8) System-onChip! Timers!
Control!
Temp.! Sensor!
Bandgap! Reference!
12-bit! ΣΔ
ADC!
PGA! LPF!
Capacitive! Interface!
16-bit! Slope! ADC!
Processor Core!
Voltage!
Analog Interface!
Watchdog!
USART!
Parallel I/O!
Parallel I/O!
MAC!
CLK Manager!
Amperometric! Interface!
Prog. Mem.!
Kraver, Guthaus, et al.
10/31/13!
Sensors in Digital Health
Data Mem.!
10
MS-8 System-on-Chip Die Photo!
IMEM
Analog
Kraver, Guthaus, et al. DMEM
Core
ROM
D. Sylvester et al. 10/31/13!
Sensors in Digital Health
11
Demonstration! Time Response: each step represents a decade jump in potassium concentration
1.8 1.7 1.6 1.5 0
200
400
600
800
1000 1.9
Time (s)
Calibration Curve for Potassium Kraver, Guthaus, et al.
10/31/13!
Output Voltage (V)
Output Voltage (V)
1.9
V = 0.0525Log(C) + 1.8211! R2 = 0.9998!
1.8 1.7 1.6 1.5
-7
-6
-5
-4
-3
Concentration 10x (M) Sensors in Digital Health
-2
-1
0
12
Calibration! • Matches actual values with theoretical model! – Linear, Quadratic, Polynomial, Exponential, PWL, etc.! – Mismatch is due to! • Manufacturing tolerance! • Environment (temperature, humidity)! • Hysteresis! • Non-ideal behavior (nonlinearity, saturation, etc.)!
• Sensors have limited range of validity! Handbook of Modern Sensors
10/31/13!
Sensors in Digital Health
13
Sensor Fabrication • Organic: biological membranes, etc.! – Often better quality measurements! – Often difficult to use (aqueous solutions)!
• Inorganic: semiconductors, thin films, etc.! – Often cheaper! – Often more durable!
Source: Freescale
MEMS: Micro-Electrical Mechanical Systems Maitra, Kim, Dunbar. Recent advances in nanopore sequencing, Electrophoresis, Dec. 2012. 10/31/13!
Sensors in Digital Health
14
Hobbyist Resources • Demo Boards! – Arduino ($25)! • Shields!
– Raspberry Pi ($25)! • Operating System!
– SensorTAG ($25)! • Bluetooth/Wireless!
10/31/13!
Sensors in Digital Health
15
Mobile Platform Sensors • • • • • • • • • •
Radio/Camera! Acceleration! Ambient Light! Proximity! Gyroscope! Magnetometer! Temperature! Humidity! Pressure! Fingerprint! 10/31/13!
Sensors in Digital Health
16
What happens next? • • • •
We already have tons of data.! We are only going to get more data.! What do we do with the data?! Pervasive sensor systems to Personalized sensor systems.! – Gathering the data.! – Managing the data.! – Mining the data.! – Acting on the data.! Dexcom continuous glucose monitoring. 10/31/13!
Sensors in Digital Health
17
