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M. Sc. Zivko Kokolanski Ph.D. Student kokolanski@feit.ukim.mk

Single point calibration applied on multivibrator -based signal conditioning circuits for passive modulating sensors. M. Sc. Zivko Kokolanski Ph.D. Student kokolanski@feit.ukim.edu.mk. OUTLINE. Introduction to signal conditioning Multivibrator in monostable and astable configuration

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M. Sc. Zivko Kokolanski Ph.D. Student kokolanski@feit.ukim.mk

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  1. Single point calibration applied on multivibrator-based signal conditioning circuits for passive modulating sensors M. Sc. ZivkoKokolanski Ph.D. Student kokolanski@feit.ukim.edu.mk

  2. OUTLINE • Introduction to signal conditioning • Multivibrator in monostable and astable configuration • Measurement uncertainty • Single point calibration • Systematic errors • Transfer characteristic • Temperature variation test • Conclusions

  3. SIGNAL CONDITIONING mC mC Sensor Oscillator Sensor Programmable signal cond. circ. A/D mC Relaxation oscillator Sensor Programmable measurement system with A/D converter Programmable measurement system with oscillator Cref,Rref Direct Sensor-to-microcontroller interface • Simple, low cost • Direct digital interface • Wider dynamic range • Lower electromagnetic interference • ADVANTAGES:

  4. MULTIVIBRATOR Basic representation of a multivibrator in monostable (a) and astable (b) configuration

  5. MEASUREMENT UNCERTAINTY • Two effects are dominant: quantization and trigger uncertain.

  6. MONOSTABLE MULTIVIBRATOR (555) FAMILY ???

  7. MONOSTABLE MULTIVIBRATOR WITH SINGLE POINT CALIBRATION

  8. SYSTEMATIC ERRORS Gain Nonlinearity Offset ForDRx<1/2LSB The condition limits the measurement range

  9. TRANSFER CHARACTERISTIC • Realization with DAQ card USB6218 • 20 MHz timebase • ENOB = 14.2 bits (0.1 ) • Measurement range 1000  to 3000  • Maximal relative error of the approximated transfer characteristic was 0.11%

  10. TEMPERATURE VARIATION TEST • Rapid temperature rise increased • Tx and Tc for 2% • Rx decreased 0.2% • Single point calibration reduce the • temperature effects nearly 10 times

  11. CONCLUSIONS • The performances of the multivibrator as a sensor signal conditioner are limited by temperature, aging and other effects • The single point calibration improves the stability of the measurements and performs temperature compensation • The input resistances and leakage currents introduce gain, offset and nonlinearity errors and limit the measurement range • The experimental results show that a resolution better than 0.1W in the measurement range from 1000 W to 3000 W with maximal relative error of 0.11% is achivable

  12. THANK YOU!

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