Experiment-Basic Concept and Test Equipment-chapter-4

Experiment-Ammeter usage Procedure

PARTS AND MATERIALS

• 6-volt battery
• 6-volt incandescent lamp

Basic circuit construction components such as breadboard, terminal strip, and jumper wires are also assumed to be available from now on, leaving only components and materials unique to the project listed under "Parts and Materials."

CROSS-REFERENCES

 "Basic Concepts of Electricity"

"DC Metering Circuits"

LEARNING OBJECTIVES

• How to measure current with a multimeter
• How to check a multimeter's internal fuse
• Selection of proper meter range

SCHEMATIC DIAGRAM

ILLUSTRATION

INSTRUCTIONS

Current, definition Ampere Amp Unit, ampere

Current is the measure of the rate of electron "flow" in a circuit. It is measured in the unit of the Ampere, simply called "Amp," (A).

The most common way to measure current in a circuit is to break the circuit open and insert an "ammeter" in series(in-line) with the circuit so that all electrons flowing through the circuit also have to go through the meter. Because measuring current in this manner requires the meter be made part of the circuit, it is a more difficult type of measurement to make than either voltage or resistance.

Some digital meters, like the unit shown in the illustration, have a separate jack to insert the red test lead plug when measuring current. Other meters, like most inexpensive analog meters, use the same jacks for measuring voltage, resistance, and current. Consult your owner's manual on the particular model of meter you own for details on measuring current.

When an ammeter is placed in series with a circuit, it ideally drops no voltage as current goes through it. In other words, it acts very much like a piece of wire, with very little resistance from one test probe to the other. Consequently, an ammeter will act as a short circuit if placed in parallel (across the terminals of) a substantial source of voltage. If this is done, a surge in current will result, potentially damaging the meter:

Fuse

Ammeters are generally protected from excessive current by means of a small fuse located inside the meter housing. If the ammeter is accidently connected across a substantial voltage source, the resultant surge in current will "blow" the fuse and render the meter incapable of measuring current until the fuse is replaced. Be very careful to avoid this scenario!

You may test the condition of a multimeter's fuse by switching it to the resistance mode and measuring continuity through the test leads (and through the fuse). On a meter where the same test lead jacks are used for both resistance and current measurement, simply leave the test lead plugs where they are and touch the two probes together. On a meter where different jacks are used, this is how you insert the test lead plugs to check the fuse:

Build the one-battery, one-lamp circuit using jumper wires to connect the battery to the lamp, and verify that the lamp lights up before connecting the meter in series with it. Then, break the circuit open at any point and connect the meter's test probes to the two points of the break to measure current. As usual, if your meter is manually-ranged, begin by selecting the highest range for current, then move the selector switch to lower range positions until the strongest indication is obtained on the meter display without over-ranging it. If the meter indication is "backwards," (left motion on analog needle, or negative reading on a digital display), then reverse the test probe connections and try again. When the ammeter indicates a normal reading (not "backwards"), electrons are entering the black test lead and exiting the red. This is how you determine direction of current using a meter.

Metric prefix

For a 6-volt battery and a small lamp, the circuit current will be in the range of thousandths of an amp, or milliamps. Digital meters often show a small letter "m" in the right-hand side of the display to indicate this metric prefix.

Try breaking the circuit at some other point and inserting the meter there instead. What do you notice about the amount of current measured? Why do you think this is?

Re-construct the circuit on a breadboard like this:

Students often get confused when connecting an ammeter to a breadboard circuit. How can the meter be connected so as to intercept all the circuit's current and not create a short circuit? One easy method that guarantees success is this:

• Identify what wire or component terminal you wish to measure current through.
• Pull that wire or terminal out of the breadboard hole. Leave it hanging in mid-air.
• Insert a spare piece of wire into the hole you just pulled the other wire or terminal out of. Leave the other end of this wire hanging in mid-air.
• Connect the ammeter between the two unconnected wire ends (the two that were hanging in mid-air). You are now assured of measuring current through the wire or terminal initially identified.

Again, measure current through different wires in this circuit, following the same connection procedure outlined above. What do you notice about these current measurements? The results in the breadboard circuit should be the same as the results in the free-form (no breadboard) circuit.

Building the same circuit on a terminal strip should also yield similar results:

The current figure of 24.70 milliamps (24.70 mA) shown in the illustrations is an arbitrary quantity, reasonable for a small incandescent lamp. If the current for your circuit is a different value, that is okay, so long as the lamp is functioning when the meter is connected. If the lamp refuses to light when the meter is connected to the circuit, and the meter registers a much greater reading, you probably have a short-circuit condition through the meter. If your lamp refuses to light when the meter is connected in the circuit, and the meter registers zero current, you've probably blown the fuse inside the meter. Check the condition of your meter's fuse as described previously in this section and replace the fuse if necessary.

Experiment-Basic Concept and Test Equipment-chapter-3

Experiment-A Very Simple Circuit

PARTS AND MATERIALS

• 6-volt battery
• 6-volt incandescent lamp
• Jumper wires
• Breadboard
• Terminal strip

From this experiment on, a multimeter is assumed to be necessary and will not be included in the required list of parts and materials. In all subsequent illustrations, a digital multimeter will be shown instead of an analog meter unless there is some particular reason to use an analog meter. You are encouraged to use both types of meters to gain familiarity with the operation of each in these experiments.

CROSS-REFERENCES

Lessons In Electric Circuits, Volume 1, chapter 1: "Basic Concepts of Electricity"

LEARNING OBJECTIVES

Experiment-Basic Concept and Test Equipment-chapter-2

 Experiment-Ohmmeter(Insulation tester)Usage

PARTS AND MATERIALS

• Multimeter, digital or analog
• Assorted resistors (Radio Shack catalog # 271-312 is a 500-piece assortment)
• Rectifying diode (1N4001 or equivalent; Radio Shack catalog # 276-1101)
• Cadmium Sulphide photocell (Radio Shack catalog # 276-1657)
• Breadboard (Radio Shack catalog # 276-174 or equivalent)
• Jumper wires
• Paper
• Pencil
• Glass of water
• Table salt

Experiment-Basic Concept and Test Equipment-chapter-1

Voltmeter usage Procedure 

PARTS AND MATERIALS

• Multimeter, digital or analog
• Assorted batteries
• One light-emitting diode (Radio Shack catalog # 276-026 or equivalent)
• Small "hobby" motor, permanent-magnet type (Radio Shack catalog # 273-223 or equivalent)
• Two jumper wires with "alligator clip" ends (Radio Shack catalog # 278-1156, 278-1157, or equivalent)

A multimeter is an electrical instrument capable of measuring voltage, current, and resistance. Digital multimeters have numerical displays, like digital clocks, for indicating the quantity of voltage, current, or resistance. Analogmultimeters indicate these quantities by means of a moving pointer over a printed scale.

Experiments-Introduction-Chapter-2

Setting up a Home Lab

In order to build the circuits described in this volume, you will need a small work area, as well as a few tools and critical supplies. This section describes the setup of a home electronics laboratory.

Work area

A work area should consist of a large workbench, desk, or table (preferably wooden) for performing circuit assembly, with household electrical power (120 volts AC) readily accessible to power soldering equipment, power supplies, and any test equipment. Inexpensive desks intended for computer use function very well for this purpose. Avoid a metal-surface desk, as the electrical conductivity of a metal surface creates both a shock hazard and the very distinct possibility of unintentional "short circuits" developing from circuit components touching the metal tabletop. Vinyl and plastic bench surfaces are to be avoided for their ability to generate and store large static-electric charges, which may damage sensitive electronic components. Also, these materials melt easily when exposed to hot soldering irons and molten solder droplets.

EIA-Experiments-Introduction-Chapter-1

    Introduction-Chapter-1 

    Electronics as Science

    Dear Readers 

Glad to inform you that we have going to provide experiments procedure  of equipment/instruments /self made device with help of your own home mad lab. The LAB experiment based on EIA (Electrical Instrumentation and Automation).

List of content which will explain in experiment topic as follows

INTRODUCTION
BASIC CONCEPT OF TEST EQUIPMENT
AC CIRCUIT
DC CIRCUITS
DISCRETE SEMICONDUCTOR CIRCUITSANALOG INTEGRATED CIRCUITSDIGITAL INTEGRATED CIRCUIT
555 TIMER CIRCUIT

Concept of Magnetic Flux and Magnetic Lines of Force

Flux and Magnetic Lines of Force

Concept of electric flux was used in connection with the electric field in whichwhic electric flux density at a point in free space is directly proportional to the electric field intensity at that point. Analogous relations exist for the magnetic field in that the magnetic flux density at a point in free space is directly proportional to the magnetic field intensity at that point, as expressed by

.      [3-15]

where B = magnetic flux density and μ0 = magnetic permeability of free space. In the rationalized MKS μ0 has the value of 4π x 10-7 henry per meter and B is expressed in webers per square meter.
The magnetic field is a field of force and requires energy for its production. A magnet when brought into the magnetic field produced by another magnet or by a current in a circuit experiences a force. Although a positive or negative charge can be isolated, a magnetic pole cannot exist by itself since every magnet has an equal number of poles of opposite polarity. The simplest magnet has one north pole and one south pole. However, if a north pole could exist by itself without the accompanying south pole, and this north pole were brought to within a distance of r1 of the filament in Fig. 3-2, it would experience a force in a direction tangent to the circle of radius r1 as determined by the right-hand rule. The locus of constant force would be a cylinder of radius r1 concentric with the filament. The magnetic field can therefore be represented by lines of force.

The Unit Magnet Pole

Magnet Pole

It is shown that electric charges produce an electric field and that forces between electric charges exist. The force between point charges isolated in free space which expresses Coulomb's law for point electrical charges. A similar law known as Coulomb's law of force between point magnetic poles applies to magnetic fields in free space and is given by the following formula

[3-19]

CONDUCTOR AND INSULATOR TABLES

Gage size, wire Wire size, gage scale
Soild copper wire table:

Size        Diameter         Cross-sectional area       Weight
AWG          inches        cir. mils     sq. inches   lb/1000 ft
================================================================
4/0 -------- 0.4600 ------- 211,600 ------ 0.1662 ------ 640.5
3/0 -------- 0.4096 ------- 167,800 ------ 0.1318 ------ 507.9
2/0 -------- 0.3648 ------- 133,100 ------ 0.1045 ------ 402.8

Concept of Magnetic Circuit

Magnetic Circuit

Magnetism that depends on a flow of electric current is called electromagnetism. Fig. 7-1 shows a typical magnetic pattern produced by a loosely wound coil or solenoid with air core.

Fig. 7-1. Solenoid With Air Core

Magnetic units of measurement

Magnetic units 

Field intensity Flux density Reluctance Permeability

If the burden of two systems of measurement for common quantities (English vs. metric) throws your mind into confusion, this is not the place for you! Due to an early lack of standardization in the science of magnetism, we have been plagued with no less than three complete systems of measurement for magnetic quantities.

First, we need to become acquainted with the various quantities associated with magnetism. There are quite a few more quantities to be dealt with in magnetic systems than for electrical systems. With electricity, the basic quantities are Voltage (E), Current (I), Resistance (R), and Power (P). The first three are related to one another by Ohm's Law(E=IR ; I=E/R ; R=E/I), while Power is related to voltage, current, and resistance by Joule's Law (P=IE ; P=I²R ; P=E²/R).

With magnetism, we have the following quantities to deal with:

Concept of Ohm's Law

Ohm's Law

These units and symbols for electrical quantities will become very important to know as we begin to explore the relationships between them in circuits. The first, and perhaps most important, relationship between current, voltage, and resistance is called Ohm's Law, discovered by Georg Simon Ohm and published in his 1827 paper, The Galvanic Circuit Investigated Mathematically. Ohm's principal discovery was that the amount of electric current through a metal conductor in a circuit is directly proportional to the voltage impressed across it, for any given temperature. Ohm expressed his discovery in the form of a simple equation, describing how voltage, current, and resistance interrelate:

Resistor Color Codes

Measurement of Power quality

Power quality 

Power quality Load, nonlinear Nonlinear components

It used to be with large AC power systems that "power quality" was an unheard-of concept, aside from power factor. Almost all loads were of the "linear" variety, meaning that they did not distort the shape of the voltage sine wave, or cause non-sinusoidal currents to flow in the circuit. This is not true anymore. Loads controlled by "nonlinear" electronic components are becoming more prevalent in both home and industry, meaning that the voltages and currents in the power system(s) feeding these loads are rich in harmonics: what should be nice, clean sine-wave voltages and currents are becoming highly distorted, which is equivalent to the presence of an infinite series of high-frequency sine waves at multiples of the fundamental power line frequency.

Y and Delta Configurations for Three-Phase circuit

 Y and Delta Configurations

Initially we explored the idea of three-phase power systems by connecting three voltage sources together in what is commonly known as the "Y" (or "star") configuration. This configuration of voltage sources is characterized by a common connection point joining one side of each source:

Practical power factor correction

POWER FACTOR CORRECTION

When the need arises to correct for poor power factor in an AC power system, you probably won't have the luxury of knowing the load's exact inductance in henrys to use for your calculations. You may be fortunate enough to have an instrument called a power factor meter to tell you what the power factor is (a number between 0 and 1), and the apparent power (which can be figured by taking a voltmeter reading in volts and multiplying by an ammeter reading in amps). In less favorable circumstances you may have to use an oscilloscope to compare voltage and current waveforms, measuring phase shift in degrees and calculating power factor by the cosine of that phase shift.

Concept of True, Reactive, and Apparent Power

 True, Reactive, and Apparent Power

We know that reactive loads such as inductors and capacitors dissipate zero power, yet the fact that they drop voltage and draw current gives the deceptive impression that they actually do dissipate power. This "phantom power" is called reactive power, and it is measured in a unit called Volt-Amps-Reactive (VAR), rather than watts. The mathemati symbol for reactive power is (unfortunately) the capital letter Q. The actual amount of power being used, or dissipated, in a circuit is called true power, and it is measured in watts (symbolized by the capital letter P, as always). The combination of reactive power and true power is called apparent power, and it is the product of a circuit's voltage and current, without reference to phase angle. Apparent power is measured in the unit of Volt-Amps(VA) and is symbolized by the capital letter S.

As a rule, true power is a function of a circuit's dissipative elements, usually resistances (R). Reactive power is a function of a circuit's reactance (X). Apparent power is a function of a circuit's total impedance (Z). Since we're dealing with scalar quantities for power calculation, any complex starting quantities such as voltage, current, and impedance must be represented by their polar magnitudes, not by real or imaginary rectangular components. For instance, if I'm calculating true power from current and resistance, I must use the polar magnitude for current, and not merely the "real" or "imaginary" portion of the current. If I'm calculating apparent power from voltage and impedance, both of these formerly complex quantities must be reduced to their polar magnitudes for the scalar arithmetic.
There are several power equations relating the three types of power to resistance, reactance, and impedance (all using scalar quantities):

Please note that there are two equations each for the calculation of true and reactive power. There are three equations available for the calculation of apparent power, P=IE being useful only for that purpose. Examine the following circuits and see how these three types of power interrelate:
Resistive load only:

Reactive load only:

Resistive/reactive load:

Power triangle
These three types of power -- true, reactive, and apparent -- relate to one another in trigonometric form. We call this the power triangle:

Using the laws of trigonometry, we can solve for the length of any side (amount of any type of power), given the lengths of the other two sides, or the length of one side and an angle.
Review
Power dissipated by a load is referred to as true power. True power is symbolized by the letter P and is measured in the unit of Watts (W).
Power merely absorbed and returned in load due to its reactive properties is referred to as reactive power. Reactive power is symbolized by the letter Q and is measured in the unit of Volt-Amps-Reactive (VAR).
Total power in an AC circuit, both dissipated and absorbed/returned is referred to as apparent power. Apparent power is symbolized by the letter S and is measured in the unit of Volt-Amps (VA).
These three types of power are trigonometrically related to one another. In a right triangle, P = adjacent length, Q = opposite length, and S = hypotenuse length. The opposite angle is equal to the circuit's impedance (Z) phase angle.

Categories of AC& DC Motor

AC&DC Motor

Lighting worked as well on AC as on DC. Transmission of electrical energy covered longer distances at lower loss with alternating current. However, motors were a problem with alternating current. Initially, AC motors were constructed like DC motors. Numerous problems were encountered due to changing magnetic fields, as compared to the static fields in DC motor motor field coils.

Hysteresis and Eddy Current in motor

Hysteresis and Eddy Current

Early designers of AC motors encountered problems traced to losses unique to alternating current magnetics. These problems were encountered when adapting DC motors to AC operation. Though few AC motors today bear any resemblance to DC motors, these problems had to be solved before AC motors of any type could be properly designed before they were built.

Both rotor and stator cores of AC motors are composed of a stack of insulated laminations. The laminations are coated with insulating varnish before stacking and bolting into the final form. Eddy currents are minimized by breaking the potential conductive loop into smaller less lossy segments below. The current loops look like shorted transformer secondary turns. The thin isolated laminations break these loops. Also, the silicon added to the alloy used in the laminations increases electrical resistance which decreases the magnitude of eddy currents.

If the laminations are made of silicon alloy grain oriented steel, hysteresis losses are minimized. Magnetic hysteresis is a lagging behind of magnetic field strength as compared to magnetizing force. If a soft iron nail is temporarily magnetized by a solenoid, one would expect the nail to lose the magnetic field once the solenoid is de-energized. However, a small amount of residual magnetization, B_r due to hysteresis remains. An alternating current has to expend energy, -H_c the coercive force, in overcomming this residual magnetization before it can magnetize the core back to zero, let alone in the opposite direction. Hysteresis loss is encountered each time the polarity of the AC reverses. The loss is proportional to the area enclosed by the hysteresis loop on the B-H curve. "Soft" iron alloys have lower losses than "hard" high carbon steel alloys. Silicon grain oriented steel, 4% silicon, rolled to preferentially orient the grain or crystalline structure, has still lower losses.

Once Steinmetz's Laws of hysteresis could predict iron core losses, it was possible to design AC motors which performed as designed. This was akin to being able to design a bridge ahead of time that would not collapse once it was actually built. This knowledge of eddy current and hysteresis was first applied to building AC commutator motors similar to their DC counterparts. Today this is but a minor category of AC motors. Others invented new types of AC motors bearing little resemblance to their DC kin.

Harmonics in Polyphase Power Systems

Harmonics

In the chapter on mixed-frequency signals, we explored the concept of harmonics in AC systems: frequencies that are integer multiples of the fundamental source frequency. With AC power systems where the source voltage waveform coming from an AC generator (alternator) is supposed to be a single-frequency sine wave, undistorted, there should be no harmonic content ideally.

Valuable 3 Strategies for Practicing Self-Respect

Practicing Self-Respect

“Self-Respect: Its Source, Its Power.” In it she wrote, “To live without self-respect is to lie awake some night, beyond the reach of warm milk, phenobarbital and the sleeping hand on the coverlet, counting up the sins of commission and omission, the trusts betrayed, the promises subtly broken, the gifts irrevocably wasted through sloth or cowardice or carelessness.”

Concept of Inrush current

Inrush current

When a transformer is initially connected to a source of AC voltage, there may be a substantial surge of current through the primary winding called inrush current. This is analogous to the inrush current exhibited by an electric motor that is started up by sudden connection to a power source, although transformer inrush is caused by a different phenomenon.

We know that the rate of change of instantaneous flux in a transformer core is proportional to the instantaneous voltage drop across the primary winding. Or, as stated before, the voltage waveform is the derivative of the flux waveform, and the flux waveform is the integral of the voltage waveform. In a continuously-operating transformer, these two waveforms are phase-shifted by 90^o. Since flux (Φ) is proportional to the magnetomotive force (mmf) in the core, and the mmf is proportional to winding current, the current waveform will be in-phase with the flux waveform, and both will be lagging the voltage waveform by 90^o: