1. Basics of Sensor Compensation for Piezoresistive Sensors
January 21, 2013 Randy Frank

2. Agenda Steps toward smart sensors Wheatstone bridge Amplification
Calibration, linearization and signal integrity techniques for piezoresistive sensors
More complex piezoresistive interfaces

3. Levels of Intelligent Sensor Processing
Knowledge Extraction
Layer 4
Information Enhancement
Layer 3
Wireless or Wired Bus Communications to
Other intelligent systems & Smart Sensors
System Awareness
Sensor Compensation
Layer 2
Data Acquisition
Layer 1
Source: Microchip Technology

4. Accurate Data & Better Decisions
Knowledge Extraction
Pattern Recognition
Classification
Prediction
Adaptive Filtering
Information Enhancement
Frequency Domain
Noise Removal
Sensor Fusion
Sensor Compensation
Calibration
Linearization
Signal Integrity
Diagnostics
Data Acquisition
Transducer
Amplification
Low Pass Filtering
A/D Conversion
Source: Microchip Technology

5. Silicon Piezoresistive Pressure Sensors
Eo = E∆R R

6. Span
Understanding Smart Sensors

7. Best Fit Straight Line Offset

8. Effect of Temperature Offset Temperature Shift (0°C-70°C),
Typical: ±0.1 mV
Temperature Effect on Resistance (0°C-70°C), typical: 2800 ppm/°C
Temperature Effect on Span (0°C-70°C),
Typical: ppm/°C
For All Sensors BLVR-L01D

9. Constant Current Source Amplifier
Also check out
And

10. Quad Op Amp Circuit TI’s TLV2474 Rail-to-rail
Rail-to-rail

11. Instrumentation Amplifier
Typical key specifications:
Operating voltage range
Rail to rail operation
Common mode rejection ratio (CMMR)
Input Voltage Noise Density
Power supply rejection ratio (PSRR)

12. Instrumentation Amplifier Example
Microchip Technology’s MCP6N11
Operating Voltage Range: 1.8 to 5.5V
Input Voltage Noise Density (nV/rt(Hz)) 35 typ
PSRR min 94 dB
CMRR min 94 dB
Piezoresistive example
Good background info:

13. 1%-Accurate Signal Conditioner
Maxim Integrated
MAX1450

14. Signal Conditioner for Piezoresistive Sensors
MAX1450
An evaluation kit is available: MAX1450EVKIT

15. Piezoresistive Interface
ZMDI ZSC31010
Sensor Signal Conditioner
CMOS integrated circuit
Designed for resistive bridge sensors
Digitally calibrate offset and gain
Internal temperature compensation and detection
Development kit available

16. Piezoresistive Interface
ZMDI ZSC31010
OWI – one wire interface
ZMDI’s ZACwire™ serial interface to the host computer and is easily mass calibrated in a Windows™ environment
Calibration performed by eeprom – no external trimmed components

17. Pressure Sensor Signal Conditioning Interface
Texas Instruments TPIC83000-Q1

18. TI’s WEBENCH Sensor Designer
Provides Analog Interface Family for:
Pressure sensors
Temperature
Load sensors
pH sensors
Chemical & gas sensors

19. TI’s AFE AFE: Analog Front End For resistive bridge sensors LMP90100
Temperature, Pressure, Load, Force and more
A complete signal path solution: sensor-MCU
Multi-channel with 16- or 24-bit Sigma Delta ADC core
Flexible, programmable mux (4 differential, 7 single-ended, or a combination inputs)
Continuous background sensor diagnostics
For resistive bridge sensors

20. TI’s AFE LMP90100

21. Summary For piezoresistive sensors
Several good sources of information exist
Simple circuits
Complex circuits
Design kits and tools simplify design-in

22. Topics Later This Week Tuesday
Basics of Sensor Compensation for Capacitive Sensors
Wednesday
A case study of smart sensor development
Thursday
Transitioning from analog sensing to the digital control world
Friday
Today’s smart sensors