Sensor Networks: Lessons 15-16 - RIS · Sensor Networks: Lessons 15-16 Prof. Sabato Manfredi...

Sensor Networks: Lessons 15-16

Prof. Sabato [email protected]+390817683845

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SIGNAL CONDITIONING

• Isolation and impedance conversion• Amplification and analog-to-analog conversion• Noise reduction• Linearization• Data sampling• Digital-to-analog conversion• Analog-to-digital conversiom

Sensor Networks - Prof. Sabato Manfredi

SIGNAL CONDITIONING: OP-AMP


SIGNAL CONDITIONING: OP-AMP


Ac=10

COMPARATOR


VOLTAGE FOLLOWER


INVERTING AMPLIFIER


NON INVERTING AMPLIFIER


SUMMING AMPLIFIER


INTEGRATOR


DIFFERENTIAL AMPLIFIER


INSTRUMENTATION AMPLIFIER


ANALOG TO ANALOG CONVERTER

Corrent to voltage converter


ANALOG TO ANALOG CONVERTER

Voltage to corrent converter


• Wheatstone bridge

WHEATSTONE BRIDGE (1/3)


∆R/R << 1

2out ref

g

R RV V

R R R

24 2

out ref out ref

RR R RV V V V

RR R R R

R

1

4out ref

RV V

R;≈



1

2out ref

RV V

R;≈

out ref

RV V

R;≈



NOISE REDUCTION


BUTTERWORTH FILTER


LINEARIZATION


DATA ACQUISITION SYSTEM


SAMPLE & HOLD


FREQUENCY SPECTRUM


ALIASING


DATA CONVERSION


DATA CONVERSION

Selection of an Analog-to-Digital Converterln addition to the usual factors of cost, size, and availability, the control system designer has the following three factors to consider in the selection of an ADC:1. Resolution is specified as the number of bits in the digital code of the output states. It determines the number of output states, the size of the LSB, and the quantization error (+ 1/2LSB). The designer must specify the minimum resolution that reduces the quantization error to an acceptable level.2. Accuracy includes other factors besides resolution, such as gain error, offset error linearity, and missing codes. Gain error is a change in the slope of the infinite resolution line from the ideal. Offset error is a displacement left or right of the infinite resolution line with no change in its slope. Linearity error is a deviation of the infinite resolution line from a straight line. Missing codes is the absence of one or more expected codes in the output as the input is traversed over its full range. When considering the accuracy of an ADC, the designer's major concern is missing codes. The gain and offset errors can be hardware adjusted or software compensated. Linearity can also be compensated but not as easily as gain and offset. Missing codes, however, cannot be restored.


DATA CONVERSION

3. Conversion speed is determined by how fast the analog signal changes, and it dictates the type of ADC selected. If the analog signal varies at a very slow speed, there is little need for a fast converter that requires fast, expensive components. If the analog signal varies at a moderate speed, the converter will have to operate faster, requiring faster, more expensive components and conversion techniques. If the analog signal varies at a high speed, both conversion techniques and component speed are of paramount importance. In general, the conversion speed requirement will dictate the type of converter selected.

• Integration based• Successive approximation• Sigma-Delta • Flash ADC


REFERENCES

R. Bateson, Inreoduction to Control system technology, Prentice Hall

[PAW91] R. Pallas-Areny and J. G. Webster, 1991, Sensors and Signal Conditioning, Wiley, New York

J. G. Webster, 1999, The Measurement, Instrumentation and Sensors Handbook, CRC/IEEE Press , Boca Raton, FL.

H. R. Taylor, 1997, Data Acquisition for Sensor Systems, Chapman and Hall, London, UK.

J. Fraden, 1997, Handbook of Modern Sensors. Physics, Designs and Applications, AIP, Woodbury, NY

J. Brignell and N. White, 1996, Intelligent Sensor Systems, 2nd Ed., IOP, Bristol, UK

Ricardo Gutierrez-Osuna, Intelligent Sensor Systems, Slides

ASHRAE Guideline 2-2005 Engineering Analysis of Experimental Data. ASHRAE, Atlanta, GA.


REFERENCES

ASHRAE Guideline 13-2000 Specifying Direct Digital Control Systems. ASHRAE, Atlanta, GA.

ASHRAE Guideline 14-2002 Measurement of Energy and Demand Savings. ASHRAE, Atlanta, GA.

Omega Instruments. The Temperature Handbook, Temperature Technical ReferenceSection, 5th Edition, 2004.

Portland Energy Conservation, Inc. (PECI) and Lawrence Berkeley National Laboratories (LBNL). Control System Design Guide, Section 3. http://www.peci.org/ftguide/csdg/CSDG.htm. February 2006.

Products Literature and Specifications (Cooper, Dwyer, Extech, Fluke, JohnsonControls, Kele, MicroDatalogger, Omega, Onset (Hobo), Setra, Siemens, Shortridge, Vaisala)


Sensor Networks: Lessons 15-16 - RIS · Sensor Networks: Lessons 15-16 Prof. Sabato Manfredi...

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