ECE471F/2001                                   Topics of the Lectures:

 

Division of the course material into lectures is tentative. There may be minor changes of the content, lecture sequence, and timing, during the term of the course.

Lectures L 1) to L 16) deal with Data Conditioning systems, lectures L 17 to L 24 with Data Conversion Systems.

 

L 1)     Basic structural arrangement of an instrumentation system and associated terminology. Data acquisition system and its components. Definitions of a transducer and a sensor. Sensor classification. Equivalent electrical models of sensors and amplifiers. Effects of interfacing on frequency response of sensor-amplifier systems. Loading error.

(The 1st Tutorial session will be an extension of the first lecture, it will include review of concepts of impedance, generalized Ohm's law, computation of transfer functions (in the s-domain and in the j domain). Construction of the Bode plot. Relationship between error and accuracy).

L 2)     Sensor specifications, equivalent electrical models, transfer characteristics, frequency range of operation , minimum signal bandwidths. Relationship between time-rate of signal-amplitude change and the minimum signal bandwidth. Grounding arrangements of instrumentation systems.

L 3)     Variable-resistance sensors: resistive temperature detectors, RTDs, thermistors. Thermocouples. Strain gauges. One, two, three, four sensor-element bridge configurations. Remote measurements, associated sources of error. Temperature measurement considerations, selection of a suitable sensor for a specific application.

L 4)     Accuracy and error. Unipolar and bipolar signals. Definitions of the full range, FR, and the full scale, FS, input and output . Absolute and relative error (expressed as % RDG (reading), % FS (full scale), SNR (signal-to-noise ratio) , ppm (parts per million), ± 1 count). In instrumentation accuracy is usually specified in % RDG or % FS. Definitions of sensitivity, resolution, responsiveness, and precision.

L 5)     Strain gauges, SG, (metal, semiconductor SG). Poisson ratio, temperature effects and compensation, self-heating error. Applications of strain-gauges in force and pressure measurement sensors. Sources of error in bridge-configuration sensors, linearization of transfer characteristics.

L 6)     Variable-capacitance sensors. Piezoelectric sensors. Linear variable differential transformer, LVDT. Principle of operation and applications.

L 7)     Sensors operating on the principle of light dependency of semiconductor p-n junctions. Photo-resistors, photo-diodes, photo-transistors. Photocells, light emitting diodes, LED. Light detectors. Optically coupled isolators an their applications.

L 8)     Ideal operational amplifier, op-amp. Inverting and non-inverting amplifiers. Non-ideal op-amps. Effects of parameters such as open-loop gain, loop gain, open-loop frequency response, DC offset, on close-loop amplifier performance. Cascading of amplifiers, input and output resistances. Differential amplifiers, reason for their use in instrumentation systems.

L 9)     Common-mode voltage, Vcm, as a major source of error in instrumentation systems (in remote measurements). Common mode current. Definition of common-mode rejection ratio, CMRR, and common-mode rejection CMR. Instrumentation amplifier and its specifications; evolution from an one-op-amp instrumentation amplifier to a three-op-amp instrumentation amplifier. Computation of the CMRR and associated common-mode error of one-op-amp instrumentation amplifier systems, effects of resistor tolerances on the CMRR.

L 10)   Three op-amp instrumentation amplifier, its advantages over one op-amp instrumentation amplifier. CMRR associated with a three-op-amp instrumentation systems and the resulting common-mode error.

L 11)   Common-mode error caused by unbalanced parasitic resistances and capacitances of interconnecting cables. Errors caused by DC offset voltage, and current, of operational amplifiers used in instrumentatin systems. Evaluation of dominant errors, reasons for placing the errors at the input of the instrumentation system. Effect of the errors on resolution and accuracy of the systems.

L 12)   Current amplifier (current-to-voltage amplifier). Charge amplifier (charge-to-voltage amplifier. Used when output impedance of a transducer approaches input impedance of an amplifier and to minimize effects of parasitic resistors and capacitors of interconnecting cables. Isolation amplifier and its applications. Definition of isolation mode rejection ratio, IMRR, and CMRR associated with the isolation amplifier.

L 13)   MIDTERM

L 14)   Noise as a source of error in instrumentation. Types of noise, sources of noise. Characterization of noise in the time-domain, using autocorrelation function, and in the frequency domain, using power spectral density, RMS value of a random noise, peak value of a random noise. Resistors and amplifiers as sources of noise. Amplifier noise model. Effective noise bandwidth. Filtered noise. Noise figure. Electromagnetic interference, EMI, and electromagnetic compatibility, EMC.

L 15)   Induced noise. Choice of shielding material to minimize effects of low-frequency electric field, low-frequency magnetic field, and high-frequency electromagnetic field interference. Choice of grounding and shielding arrangements of interconnecting cables to minimize errors caused by presence of common-mode signals.

L 16)   Design considerations, EMC, when digital current pulses are transmitted. Summary of major parameters, i.e. common mode voltages, induced noise, resistor and amplifier-generated noise, DC offset voltage and current associated with op-amps, that contribute to the overall input error of sensor-amplifier systems. Evaluation of the overall input error of sensor-amplifier systems

 

L 17)   Data Conversion Systems and associated terminology. Sampling, quantization, encoding. Components of Data Conversion System. Sampling in the time-domain. Pulse-code-modulation, PCM. Sampling error, absolute and relative, expressed in %FS or as SNR (signal-o noise ratio). Maximum and average sampling error of unipolar and bipolar signals. Choice of the sampling frequency based on the sampling error requirements. Definitions of oversampling and oversampling factor. Sampling error in the frequency-domain, minimization of the sampling error by filtering.

L 18)   Graphical representation of sampled signals (ideal and practical sampling is considered), in the time-domain and the frequency-domain; supported by Discrete Fourier Transform and the concept of convolution (convolution in the time-domain constitutes multiplication in the frequency-domain and vice versa).

 

L 19)   Design components of data conversion system, analog multiplexer, AMUX, and sample-hold device, SHD; their functions and limitations. Key parameters of AMUX, switching time and on-resistance. The key parameter of SHD, the acquisition time. Concept of time skewing.

L 20)   Presampling (antialiasing) filter and its implementation. Reason for the use in instrumentation systems.

L 21)   Analog-to-digital converters, ADC; evolution of conventional ADC from the counter type to the successive approximation ADC. Process of quantization. Quantization error.

L 22)   Dual-slope ADC, parallel ADC, voltage-to-frequency ADC.

L 23)   Tracking ADC, Delta ADC. Delta-Sigma ADC, noise shaping, lowering of the quantization noise through processes of oversampling, decimation, and filtering.

L 24)   Various arrangements of Data acquisition systems. Design components and structural arrangements of data distribution, and data recovery systems. Summary of design criteria for instrumentation systems.