lecture01(1)

Some material from Electrical Engineering: Principles and Applications, 6eAllan R. Hambley / Copyright ©2014 by Pearson Education, Inc.

EE231 Electronic Instrumentationand Sensors / Slide 1

Lecture 01



EE231 Electronic Instrumentation and SensorsDr John Breslin, NUI Galway



Learn how principles of electronic instrumentation and sensors apply to specific and interesting problems in your own fields



Overview of course topics

• Review of systems: inputs, outputs, system blocks. Overview of electrical circuit analysis and theorems. Introduction to measurement and instrumentation systems. Sensors, actuators and transducers. Sensed quantities. Passive sensors and active sensors. Resistors, capacitors and inductors as sensing elements. Practical sensor applications (e.g. galvanometer, Wheatstone bridge, switches and relays). Sensor characteristics. Control systems and frequency response. Noise, interference and errors in measurements. Signal conditioning and filtering. Analogue and digital sensors. Analogue-to-digital conversion and digital-to-analogue conversion. Analogue and digital display of sensed values. Data acquisition and instrument control using a computer.









Will illustrate principles with practical examples

• Measuring strain and position with resistors

• Cardiac pacemaker• Active noise control• Use of GPS in surveying• …



Optional course book

• Electrical Engineering: Principles and Applications, 6e (ISBN 0133116646) Allan R. Hambley, Prentice Hall / Pearson

Education, Inc.

• We will cover the first nine chapters• I am trying to organise a lower-cost

abridged version with just these chapters (ISBN 1269282530)



If you do want to buy it, some secondhand options

• abebooks.co.uk Search for “electrical engineering

hambley”, any edition will be fine

• play.com or amazon.co.uk/.com There are quite a few “used” options for

20-30 euro

• Have also ordered 10 copies for the NUI Galway library



Engineers Ireland POs



EE231 learning outcomes (LOs)

1. State the general characteristics of electronic measurement systems using sensors, and the differences between various types of sensor technologies [POa, POb].

2. Derive expressions for the outputs and frequency responses of a variety of sensor systems based on the inputs and sensing elements deployed [POa, POb].

3. Analyse and calculate how a practical measurement system can function for expected and unexpected inputs [POa, POb, POc].

4. Design and develop sensors using computer-based simulation tools, and share designed circuits publicly [POa, POb, POc, POe, POf].

5. Conduct and report on lab exercises to create a computer-based instrument control [POa, POb, POc, POe].



Assessment methods

• Written exam paper (70%) As this is a new subject, I will create a

sample paper to illustrate structure

• Online assignments (15%) Using CircuitLab, other simulation tools From week 5

• Computer lab exercises (15%) Using LabView, OrCAD, etc. From week 9





Monday lab slot

• There are no scheduled formal labs in this slot

• We are booking a computer lab for use in this slot, where you can work on your online assignments and computer lab exercises Ignore the timetabled room number (just

a placeholder) Room to be announced later



Blackboard

• All slides will be added to Blackboard• The module area does not exist yet

Academic simplification has resulted in 500 new modules being created, so there is some backlog to be anticipated – sorry



Online resources

• http://wps.prenhall.com/esm_hambley_ee_4/ Open access (later editions are closed) Includes solutions and LabView files

http://wps.prenhall.com/esm_hambley_ee_4/

http://wps.prenhall.com/esm_hambley_ee_4/



1 INTRODUCTION



1.1 Overview

• Electrical and electronic engineering systems have two main objectives:1. Gather, store, process, transport and

present information2. Distribute, store, and convert energy

between various forms Manipulation of energy and

information are often interdependent; require instrumentation and sensors



What’s a sensor? [more later]

• Sensors are devices that convert physical measurements to electrical signals



Example: weather prediction

• Data about: cloud cover, precipitation, wind speed...

• Gathered by: weather satellites, land-based radar

stations, sensors in weather stations

• Transported by: electronic communication systems

• Processed, displayed by: computers and other instrumentation



Application: engine ‘knock’

• Used to control ignition systems of internal combustion engines

• Timing of the ignition spark is critical Good performance, low pollutants Depends on fuel quality, air

temperature, throttle, engine speed…

• If ignition point occurs beyond point of best performance, sharp metallic noise due to pressure fluctuations



FIGURE 1.1 Pressure versus time for an internal combustion engine experiencing knock. Sensors convert pressure to an electrical signal that is processed to adjust ignition timing for minimum pollution and good performance.



Application (continued): Sensing pressure fluctuations

• By connecting a sensor through a tube to the combustion chamber, an electrical signal proportional to pressure is obtained Circuits process this signal to determine

whether the rapid pressure fluctuations characteristic of knock are present

Other circuits continuously adjust the ignition timing for optimum performance while avoiding knock



1.2 Circuits, currents and voltages

• Circuit theory is a fundamental tool, which we will cover first

• Embedded computers, sensors and electronic circuits – covered later - will be an increasingly important part of the products you design and the instrumentation you use as an engineer



Figure 1.3 An electrical circuit consists of circuit elements, such as voltage sources, resistances, inductances, and capacitances, connected in closed paths by conductors.



Figure 1.2 The headlight circuit. (a) The actual physical layout of the circuit. (b) The circuit diagram.



This simple description of a headlight circuit is for older cars

• In a modern car, sensors provide information to an embedded computer about the ambient light, whether ignition is energised or not, whether car is parked or in gear…

• Dashboard switch is now a logic level indicating the intent of the driver with regards to headlights



Headlight circuit (continued)

• When the ignition is turned off AND it is dark, the computer keeps the lights on for a few minutes so the passengers can see to exit Then it turns them off to conserve

energy in the battery



An emerging trend

• This is typical of the trend to use highly-sophisticated electronic and computer technology to enhance the capabilities of new designs in all fields of engineering



Electronics in cars and trucks

• The electronic content of the average car is growing rapidly in value Aim to provide increased functionality at

lower cost

• In-class exercise (3-4 minutes) Make a list of sensors and

instrumentation you can think of in a typical modern car



Table 1.1 Current and Emerging Electronic/Electrical Applications in Automobiles and Trucks



Table 1.1 (continued) Current and Emerging Electronic/Electrical Applications in Automobiles and Trucks



Electrical current, i

• i is the flow of electrical charge q through a conductor or circuit element

• The electrical current flowing through a cross section of a conductor / circuit element in a reference direction is given by i(t) = dq(t) / dt



Figure 1.4 Current is the time rate of charge flow through a cross section of a conductor or circuit element.



Reference directions

• We may not initially know the actual direction of current flow Arbitrarily select a reference direction Later if you find that a particular current

i2 = -2 A (next slide), you will know that the current actually flows in the direction opposite to the reference initially selected



Figure 1.6 In analyzing circuits, we frequently start by assigning current variables i1, i2, i3, and so forth.



Direct current and alternating current

• Recall: DC = direct current

Single direction, constant with time AC = alternating current

Reversing direction periodically, varies with time

Not just sinusoidal waveforms: any time-varying waveform such as square, triangular, etc.



Figure 1.7 Examples of dc and ac currents versus time.



Figure 1.8 Ac currents can have various waveforms.



Double-subscript notation for currents

• So far have used arrows alongside a conductor / circuit element to indicate reference directions

• Can also label ends of an element, and use double subscripts to define the reference direction



Figure 1.9 Reference directions can be indicated by labeling the ends of circuit elements and using double subscripts on current variables. The reference direction for iab points from a to b. On the other hand, the reference direction for iba points from b to a.

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