Electronic instrumentation Important Analog and Digital Signals in TD. Lecturer: Dr. Samuel Kosolapov

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1 Electronic instrumentation Important Analog and Digital Signals in TD Lecturer: Dr. Samuel Kosolapov

2 Items to be discussed Sin/Cos wave Pulse Wave (Square Wave). Duty cycle Sawtooth Wave Triangle Wave Heaviside Step Function Dirac Function Examples of Medical Signals 2

3 Example of Important Analog Voltage Signal: Sine Wave V V f t V sin 2 f t V sin 2 V sin t 0 2 f 0 Peak Value, Frequency 0 Parameters : Amplitude, ( Hz, khz, MHz, 1 f ; T Period ; T Angle Frequency t T GHz ) : 0 radian Mind SI units rules: khz and not Khz Please do not forget 2 Pi during exam / sec 3

4 Example: Sine Wave T: Period 1 sec V V t 1 sin 2 1t f 1Hz ( Hertz); T 1sec(second); 2 f V Volt rad sec radian second Vo Peak Value Amplitude Vpp Peak-to-Peak Value = 2 Vo 4

5 Example: Sine Wave OLD Style analog scope: How to measure Vo and Vpp OLD Analog Scope: it was hard to measure Vo (where is Zero Line???) it is much easier to measure Vpp (from lower to upper signal level. (use fingers ) Vertical signal shift is not important here (explain why) + explain why scope must be calibrated & zeroed before usage if Vo must be measured Vpp is more universal concept than amplitude. It is not always obvious where the amplitude is, but Vpp can be easily evaluated In case of noise: Vpp can be easily evaluated approximately, by human eye, but this may be good enough 5

Modern Digital scope: How to measure Vpp Modern digital scopes has a special means (cursors) + menu for math operations (V1+V2, V1-V2, etc.) Digital scope store signal as an array.

6 Modern Digital scope: How to measure Vpp Modern digital scopes has a special means (cursors) + menu for math operations (V1+V2, V1-V2, etc.) Digital scope store signal as an array. Simple algorithm can find Min and Max values in the relevant time interval automatically. Then Vpp = Max Min can be presented. Another (more sophisticated) algorithm can find closest local minimum and local maximum. But this algorithm may fail in case of noise In some cases digital scope automatic calculations may be wrong 6

scopes averaging function can be used Humans are still better in noise cleaning than simple computer algorithms.

7 Example: Sine Wave Modern Digital scope: How to measure Vpp. Problems Be sure that signal is clean from noise and not distorted when providing automated measurements with digital scopes averaging function can be used Humans are still better in noise cleaning than simple computer algorithms. Beware of alias when signal frequency is close Nyquist Frequency High quality analog LPF Filter is a must before ADC You must be professional EE to properly use simple and automatic digital scope 7

8 Example of Sine Wave Effective (RMS) Value V RMS V o 2 Heat equivalent Can be used for pure sine/cosine wave only!!! Integral must be used for any other signal WE WILL MOSTLY USE AMPLITUDE Vo (or Peak-to Peak value) Vpp 8

9 Practical Examples of Sine Wave Analog Electronics: Practical Frequency ranges Audio RF - Optics Name Abbr. Frequency Usage Extremely low frequency ELF 3-30 Hz Communication with submarines Audio (hi-fi) au 20 Hz 20 khz High Fidelity Audio: speech & music Low frequency LF MHz Amateur radio: USA 160 meters Medium Frequency MF MHz AM broadcasts High Frequency HF 3-30 MHz Shortwave broadcasts, RFID Very high frequency VHF MHz FM, TV, aircraft-to-aircraft communication Ultra high frequency UHF MHz TV, microwave ovens, mobile phones, wireless LAN, Bluetooth, ZigBee, GPS Super high frequency SHF 3-30 GHz Wireless LAN, radars, communications satellites Future: Optics ( ~ Hz) Gamma Rays (~10 18 Hz) 9

10 Practical Examples of Sine Wave Analog Electronics: Practical Frequency ranges Much More detailed tables are practically used: Frequency range is a valued strategic resource today like oil Many abbreviations and buzz names For Exact definitions see LAST official materials 10

Practical Examples of Sine Wave Analog Electronics: Practical Frequency ranges Polite advice: never invent words like Super, Very Hugh, Ultra High etc.

11 Practical Examples of Sine Wave Analog Electronics: Practical Frequency ranges Polite advice: never invent words like Super, Very Hugh, Ultra High etc. In a number of years this will looks funny Example: SVGA of 1989 : 1024x768 IMPORTANT: Never transmit RF before checking rules and possible punishment(s) 11

12 Practical Example of Sine Wave Electronics: Practical Voltage ranges For Exact definitions see LAST official materials The International Electrotechnical Commission (IEC) defines low voltage as any voltage in the range V AC or V DC. For Electronics those voltages are very High (especially 1500 V) We will not speak about voltages above ~ 50 V (except limited number of cases) Typical laboratory signal generator generates voltages in the range 1 mv 50 V Sometimes signals are smaller ~ 10 uv (mkv, mv) Dealing with signals smaller then 1 uv (mkv) is very problematic because of noise Arduino UNO R3: Never apply voltage < 0 V and/or >5 V to Arduino pins Some Arduino boards uses 3.3 V 12

Practical Example of Sine Wave Electronics: Practical Sensors Voltage ranges In the

Experiment: while using scope try to position cellular phone near wires and call some

What about lamps, motors of air conditioner, etc Q1. Why Faraday cage may be useful?

13 Practical Example of Sine Wave Electronics: Practical Sensors Voltage ranges In the typical educational Electronics Laboratory practical voltage limit is ~ 10 mv Do Experiment: while using scope try to position cellular phone near wires and call some other telephone. What will You see? What about lamps, motors of air conditioner, etc Q1. Why Faraday cage may be useful? Q2. Why Shielded wires are used? Many analog sensors produces signal < 1 mv filters, amplifiers, and sophisticated algorithms must be used 13

14 Example of Sine Wave Electronics: decibell (db) The DeciBell (db) originates from methods used to quantify reductions in audio levels in telephone circuits (~1920). Original definition is for Power. P db 10log 10 P1 P 0 For Voltages V 1 V 20log 10 because P ~ V0 R V db 2 For example: V 1 = 1V, V 0 = 100 mv; Then VdB = 20 db +3dB ratio means V V 1 0 ~ 1 2 ~

15 Example of Sine Wave Electronics: decibell (db) The decibell is also commonly used as a measure of gain or attenuation db units are used when we want to compare (and plot) different Voltages in case the voltages can vary in a wide scale (say, from uv to V) Warning: Exact practical definition of db contains some specific details concerning cable resistance We omitted this for now. Q1: PdB = +10 db. What Relative Increase of Power is? A = 10 The same for the Voltage? A= 20 Q2: PdB is 30 db.? A = 10* log (10^3) = 10*3 The same for Voltage? A = 60 15

16 Example of Sine Wave Electronics: dbm P db 10log 10 P1 P 0 Important unit is dbm: abbreviation for the power ratio in db when P 0 is 1 mw (milliwatt) Example: 0dBm means Power of 1 mw. +3dBm is ~ 2mW; -3dBm means 0.5 mw Some additional examples: Typical transmitter of FM radio with 50 km range is ~ 100 kw 80 dbm Typical thermal radiation emitted by a human body Maximum output of Class 1 mobile phone (Can You boil popcorn with this?) WiFi transmission power in laptops ~ 100W 50 dbm ~ 2W 33 dbm ~ 32 mw 15 dbm 16

17 Example of Sine Wave Electronics: dbm P db 10log 10 P1 P 0 Typical transmitter of FM radio with 50 km range is Typical thermal radiation emitted by a human body Maximum output of Class 1 mobile phone (Can You boil popcorn with this?) WiFi transmission power in laptops ~ 100 kw 80 dbm ~ 100W 50 dbm ~ 2W 33 dbm ~ 32 mw 15 dbm At least remember order of those numbers when non-professionals (which never learned logarithms) discuss radiation issues. Beware when business or political interests of any kinds are used in scientific or technological discussion Demonstrate how EE can prove for uneducated auditory anything he/she wants: (example of Dog on the Mars weak effect) 17

18 Example of Important Analog Voltage Signal: Pulse Wave (Square Wave) (Compare with sin wave) Pulse Wave Signal looks like Digital signal, but is widely used in Analog Electronics Q1: Can one use RMS with Pulse Wave? A: Yes, but this is not sqrt(2)!!!! (Simple) integral must be calculated!!! 18

19 Example of Important Analog Voltage Signal: Biased (Shifted) Sin and Pulse Wave Concepts: Bias, Offset, DC Shift Explain DC shift: bias: +DC Q1. Propose simple circuit having DC battery, resistors and capacitors For DC-Biasing of SIN signal Arduino Analog pins accepts signals in the range {0..5 V}. Q. How to cope with negative part of the signals? 19

20 Example of Important Analog Voltage Signal: Sawtooth Wave This signal is used in the Analog Electronics to check linearity (details later) Digital Version of this signal is used in some ADC designs (details later) 20

21 Laboratory Instrument: Laboratory Signal Generator Bias (Offset) can be set Generally signal amplitude can be set but can not be measured It is assumed that amplitude is measured by attached oscilloscope Generates Sin, Pulse, Sawtooth, Triangle + many others useful waves 21

Summary of Basic Analog Voltage Signals: Sine wave, Square wave, Triangle wave, Sawtooth wave Virtual Laboratory Instrument: Signal Generator Q1: How to

22 Summary of Basic Analog Voltage Signals: Sine wave, Square wave, Triangle wave, Sawtooth wave Virtual Laboratory Instrument: Signal Generator Q1: How to evaluate Frequency for presented signals? Q2: Do You see that p-p can be easily evaluated for any of those signals whereas amplitude evaluation is problematic? 22

Explain how Bias (Ofset) can be set, what duty cycle is Explain: Simulation is

23 Virtual Laboratory Instruments (simulation): Usage of Oscilloscope & Signal Generator Generates Sin, Pulse, Sawtooth, Triangle + many others useful waves Explain how Bias (Ofset) can be set, what duty cycle is Explain: Simulation is actually DIGITAL, in some situations simulation can be WRONG EE can not rely on simulation only!!!!! 23

24 Analog Signal: Measurements Laboratory Instruments: Multimeter, Signal Generator & Oscilloscope Q1: Can you use Multimeter to measure frequency & magnitudes of the signal? 24

25 Example of Important Analog Voltage Signal: qt, H(t), u(t) Heaviside (step) function Maple default definition Above is non-electronic Analog signal must be defined for any t (or x) Black magic must be used: Problem: Voltage is changed TOO Fast Which means that electrons must change their speed in 0 time a == infinity Force == infinity 25

26 Example of Important Analog Voltage Signal: qt, H(t), u(t) Heaviside (step) function More realistic Analog definition F1:=proc(t,s) if t < -s/2 then 0 elif t > s/2 then 1 else 1/2+t/s fi end: plot( 'F1(t,1)', 't'=-2..2); #1 When s 0, F 1 (t) q(t) S 26

27 Example of Important Analog Voltage Signal: qt, H(t), u(t) Heaviside (step) function When s 0, F 1 (t) q(t) This way EE may imagine real but very fast switch (Math presentation of an Electric Switch) 27

28 Example of Important Theoretical Analog Voltage Signal: Dirac dt function 28

29 Example of Important Theoretical Analog Voltage Signal: Dirac dt function MAPLE old definition: The Dirac(t) delta function is defined as zero everywhere except at t = 0 where it has a singularity. It also has the property that Integral(Dirac(t),t = -infinity..infinity) = 1 Looks NON-ALGORITHMIC. MAPLE new definitions: In all these formulas epsilon represents a sufficiently small real number. In practical applications, as soon as epsilon becomes negligible compared to the x values involved in the problem, it becomes impossible to distinguish between these alternative representations 29

30 Example of Important Theoretical Analog Voltage Signal: Dirac dt function F2:=proc(t,s) if t < -s/2 then 0 elif t > s/2 then 0 else 1/s fi end: Area: s*(1/s) = 1; When s 0, F 2 (t) d(t) Explain s and 1/s 30

31 Example of Important Theoretical Analog Voltage Signal: Dirac dt function When s 0, F 2 (t) d(t) The way EE may imagine Dirac s function 31

32 Example of Important Theoretical Analog Voltage Signal: Heaviside & Dirac functions: Properties d ( t) dt dq ( t) d ( t) q ( t) dt f ( t) d ( t 0 0 d ( t) dt 1 ) dt f ( ) t d ( ) d The last formula is very important: Value Extraction: Delta is non zero only when t is near. This region is really small f(t) is ~ constant there f(t) ~ f() Constant out of integral integral of d is 1. 32

33 Medical Signals. A umber of Medical Devices (monitors) used to measure signals produced by a human body in order to get important diagnostic information 33

34 Medical Signals. ECG Propose Formula (or algorithm) describing this signal 34

35 Sorry, this Quiz is for PhD: Math Model of ECG Signal ECG is a clinical diagnostic tool 35

36 More examples of medical signals. EEG (ElectroEncefaloGram). electrical activity produced by brain EEG is a clinical diagnostic tool 36

37 More examples of medical signals. EMG (ElectroMioGram). electrical activity produced by skeletal muscles 37

38 More examples of medical signals. ERG (ElectroRetinoGram). electrical activity produced by eye 38

39 More examples of medical signals. ERG (ElectroRetinoGram). electrical activity produced by eye ERG is a clinical diagnostic tool 39

PRINCIPLES OF COMMUNICATION SYSTEMS. Lecture 1- Introduction Elements, Modulation, Demodulation, Frequency Spectrum

PRINCIPLES OF COMMUNICATION SYSTEMS Lecture 1- Introduction Elements, Modulation, Demodulation, Frequency Spectrum Topic covered Introduction to subject Elements of Communication system Modulation General