The simplest method of measuring frequency with an oscilloscope, is to determine [using the gratitude] the distance between two identical points in a waveform and multiply this by the timebase setting to obtain the period and hence the frequency. This method whilst quick, is subject to at least at 5 percent error. More accurate methods of frequency measurement using an oscilloscope, utilize it as display detector in comparison techniques, employing a stable known frequency from an external source and the scope’s x-y display facility.
Consider first the problem of adjusting an oscillator’s output frequency to be equal to that of a standard frequency signal.
Applying one of this signals to all x plates of the oscilloscope and the other to the plate will result in an eclipse type display that will vary in shape at a rate dependent on the difference in frequency between two signals. As the oscillators frequency is adjusted to be equal to the standard frequency, the frequency of the eclipse will become slower and when the two frequencies are equal, will cease altogether. Thus, it becomes apparent that differences between two signals which have approximately equal frequency may be determined by counting the rotations of the eclipse in a known time. In this manner, extremely accurate frequency comparisons may be made using an oscilloscope. For example, if an oscillators output frequency changes with respect to a 1KHz standard by one cycle [one rotation of the display] is 0s, then the difference in frequency between the two is a tenth of Hz or 0.01 percent.
Another method of determining frequency ratios using an oscilloscope is to supply a common frequency to the X and Y inputs, these voltages having a 900 phase shift [to give a circular display], and applying a higher frequency signal to the Z modulator input. This higher frequency signal varies the intensity of the circular display, there being one bright and one dark section, for each multiple of X-Y input frequency. This method, whilst giving a display which is easy to interpret is limited in application to extract multiples of input frequencies, with the additional requirement that the Z nput frequency must be larger than the X-Y input.

Answer 

The current coils is connected in series with the line, and the voltage coil is connected across the line, both coils are wound on a metal frame of special design provided two magnetic circuit. A light aluminium disk is suspended in the air gap of the current to flow in the disk. The reaction of the voltage coil creates a torque [motor action] on the disk, causing it to rotate. The developed torque is proportional to the field strength of the voltage coil and the eddy current.

Uses Of Oscilloscope

1. Voltage Measurement: The parameter of voltage which is most easily determined using an oscilloscope is for a sine wave, the peak to peak value. Note: Peak to peak voltage = 2 value [for a pure sine wave].
2. Current Measurement: The oscilloscope is high input impedance instrument, and therefore cannot be directly used for the measurements of current. Currents can of course be measured as voltage drops across resistors for this purpose because unless a differential input amplifier is being used as one side of the voltage resistor will have to be at earth potential.
3. Phase Angle Measurement: An approximate measurement of the phase angle between two voltages may be performed using the graticule of a dual trace oscilloscope to determine first, the length of a complete cycle, and then the separation of the peaks of the two voltages waveforms on the two traces.
4. Frequency measurement: A sinusoidal trace on the face of C.R.O has a peak-to-peak amplitude of 5.6cm and two circles are completed in an X- displacement of 9cm. If the Y-gain control is set at and the time base control at 1ms/cm. Determine the r.m.s value of waveform and it’s frequency.

1. Types Of Motion: Whether the motion to be measured is translational or rotational look.
2. Contact: Whether the device can be made to be in contact with the moving object or it has to be in close proximity to the object without touching it.
3. Relation Of Output To Motion: Whether the output of the device is to be proportional to displacement, velocity or acceleration.
4. Time Dependence: Whether the motion to be measure is static or dynamic.
5. Magnitude Of Motion: Whether the motion to be measured is small or large. The motion can be of the order of a few micros or a few centimetres.

1. Experimental Design Studies: The design and development of a new product generally involves trial-and-error procedures which generally involves the use of empirical relations, handbook data, the standard practises mentioned in design codes as well as design equations based on scientific theories and principles.
2. To Perform Various Manipulations: In a number of cases, the instruments are employed to perform operations like division, differentiation, integration, signal linearization, signal sampling, signal averaging, multi-point correlation ratio controls e.t.c
3. Testing Of Materials, Maintenance Of Standards And Specification Of Products: Most countries have standard organisations that specify materials standards and product specification based on extensive tests and measurements. These test are been done so as to protect the interest of the consumers.They ensure that the material/products meet the specified requirements, so that they function properly and enhance the reliability of the system.
4. Verification Of Physical Phenomena/Scientific Theories: Quite often experimental data is generated to verify a certain physical phenomenon. Whether a scientist or an engineer proposes any theory predicting a system’s behaviour. It needs to be checked to put the same on a sound factory.
5. Quality Control In Industry: it is quite common these days to have continuous quality control tests of mass produced industrial products. This enables to discover defective components that are outright rejected at early stages of production. Consequently, the final assembly of the machine/system is free from defects.

What is an electrodynamics instrument

Electrodynamic instrument is an instrument that depends on its operation on the reaction between the current in one or more movable coils and the current in one or more fixed coil. Describe the working principle of electrodynamic power factor meter. [7 marks]

Describe the working principle of electrodynamic instrument.

Electrodynanometer is used extensively in measuring power. It may be used to indicate dc and ac power for any waveform of voltage and current. Electrodynamometer employs a pair of stationary coils instead of the permanent magnet. The Electrodynamometer used as a voltmeter or an ammeter has fixed coils and the movable coil connected in series, usually to measure power dissipation wattage, two regular meters power required, one connected as a voltmeter and the other one as an ammeter. Since product of voltage and current is power. However by using electrodynamometer, a single motor can read the wattage directly. An electrodynamometer-watt meter consists of stationery coils L1 and L2 connected as an ammeter in series with the circuit being measured, while the movable coil L3 with a suitable multiplier resistor is connected as a voltmeter across the component or circuit being measured. The amount of rotation of reflection of coil L3 and its pointer, is directly proportional to the current flowing through voltage across the movable coil L3. The result is that the rotation of L3 is actually proportional to the product of voltage and current, and the meter scale may be calibrated in watts. QUESTION FIVE Describe the working principle of wattmeter [4 marks] Describe the working principle of wattmeter Answer The current coils is connected in series with the line, and the voltage coil is connected across the line, both coils are wound on a metal frame of special design provided two magnetic circuit. A light aluminium disk is suspended in the air gap of the current to flow in the disk. The reaction of the voltage coil creates a torque [motor action] on the disk, causing it to rotate. The developed torque is proportional to the field strength of the voltage coil and the eddy current.nswer
Electrodynamic instrument is an instrument that depends on its operation on the reaction between the current in one or more movable coils and the current in one or more fixed coil.

Describe the working principle of electrodynamic power factor meter.

Describe the working principle of electrodynamic power factor meter.
Electrodynanometer is used extensively in measuring power. It may be used to indicate dc and ac power for any waveform of voltage and current. Electrodynamometer employs a pair of stationary coils instead of the permanent magnet. The Electrodynamometer used as a voltmeter or an ammeter has fixed coils and the movable coil connected in series, usually to measure power dissipation wattage, two regular meters power required, one connected as a voltmeter and the other one as an ammeter. Since product of voltage and current is power. However by using electrodynamometer, a single motor can read the wattage directly.
An electrodynamometer-watt meter consists of stationery coils L1 and L2 connected as an ammeter in series with the circuit being measured, while the movable coil L3 with a suitable multiplier resistor is connected as a voltmeter across the component or circuit being measured. The amount of rotation of reflection of coil L3 and its pointer, is directly proportional to the current flowing through voltage across the movable coil L3. The result is that the rotation of L3 is actually proportional to the product of voltage and current, and the meter scale may be calibrated in watts.

Describe the working principle of wattmeter

The current coils is connected in series with the line, and the voltage coil is connected across the line, both coils are wound on a metal frame of special design provided two magnetic circuit. A light aluminium disk is suspended in the air gap of the current to flow in the disk. The reaction of the voltage coil creates a torque [motor action] on the disk, causing it to rotate. The developed torque is proportional to the field strength of the voltage coil and the eddy current.

Factors for selecting instruments for measurements

Describe the factors listed in Q3(a) above. [6 marks]These are various factors to be considered when selecting instrument for measurement. They are Range, Accuracy, Response, Input, Output, Stability, Operation, Reliability and Sensitivity.
(1) RANGE: This can be defined as the difference between the nominal value of the measures quantities corresponding to the scale in which the instrument can measure.
(2) ACCURACY: This can be defined as the extent to which the indicators of an instrument approach the true values of the quantities measured.

Factors that can affect the accuracy of the indicator of an instrument are:

1. Temperature: Some instruments like analogue are affected by atmospheric condition.
2. Humidity: Moisture can affect instrument.
3. Voltage: There is a limit to which a very low or high voltage can give accuracy since the voltage of the instrument used is not corresponding to what is been measured.
4. Waveform: It’s important to understand the types of waveforms associated with vibration analysis which may cause variation of units.
5. Proximity [to other instruments]: its closeness or how other instrument can reach also matters.
6. Overload: If the load measured is more than the instrument scale it may bring about inaccuracy or the instrument damage. Take for instance, if an ammeter used in the laboratory which does not have a maximum range of scale is used to measure HIGH TRANSMISSION line electricity, what do you think will happen, of course there will be damage of the instrument..
7. Vibration: Vibration of an instrument to be measured may cause variation of units or scale.

(3) RESPONSE: This can be defined as the performance of the instrument or measuring system to the full effect of an input signal. If it do not show quickly, it is due to a lag or delay. This delay is called measurements lag.
Input: This can be defined as the energy that is measured by an instrument that have the same range with it. OR This can be defined as the useful energy an instrument of measuring device can take once at a particular time.
(4) STABILITY: This can be defined as the ability of an instrument to return to it’s initial [zero reading] after the measured quantities has returned to zero. ( if an instrument after measuring an input can return to its initial scale, it is said to be stable).

(5) OUTPUT: This is the opposite of input. It simply means the useful energy an instrument or measuring device can deliver at a particular time.

(6) OPERATION: This is the ability of an instrument to work or perform its function within a stated format, procedure, limit and standard.
The standard are classified as;
International standard
Primary standard
Secondary standard
Working standard

(7) RELIABILITY: This is the ability of an instrument to perform a required operation/function under a stated condition for a stated period of time.

(8) SENSITIVITY: This is the response of an instrument to be able to observe every change that happens in its surrounding or environment. OR is the relationship between a change in the output reading for a given change of the input.

LIST FOUR [4] BASIC ACTIONS DEVELOPED IN A SIMPLE METER OPERATION OF A RELATIVELY COMPLICATED INSTRUMENTATION PROCEDURE

Acquisition – .it is the process of getting materials needed
Preparation – It is used to retrieve, arranged or setup.
Processing- it is the process of working on the materials
Interpretation- it is the process of interpreting the information

Explain the following terms and state their applications in industry

• Pressure
• Flow
• Temperature
• Level
• Humidity

Describe the following terms and state their applications in industry

• Temperature
• Humidity
• Viscosity
• Motion
• Level
• Pressure
• Flow

1. Temperature: Temperature is the degree of hotness or coldness of a body [object] or an environment measured on a definite scale. Application: It is generally applicable in industry where chemical action are needed because; in the industry processes and products and desired quality that is required to be obtained is only achieved if the temperature is accurately measured. Furthermore, it forms an important governing parameter in the thermodynamics and heat transfer operations like steam, gas, turbines in power generations and also in numerous propulsion systems. In addition, in the heat treatment of steel and aluminium, alloys, temperature measurement is used to obtain the desired shape and quality of the material.
2. Humidity: Humidity can lead to improved quality, optimum product weight and increased machine speed and efficiency of a machine. Application: Flunctuation in air humidity and poor humidification levels can cause serious damages to machinery, escalate injury and leads to a halt in production.
3. Viscosity: is defined as the resistance to flow. Resistance to flow means that the particles can move around, but it may be difficult for them to pass by each other. Viscosity decreases as the fluid is heated and increases as the fluid is cooled. Application: The viscosity of some medication such as the various fluids used to remove warts, has also been modified for easier application.Drug companies manufacture medicines, such as cough syrup, that have a high viscosity yet are still drinkable, in order to coat and soothe the throat.
4. Motion: The way in which things move.
   Application: In the world of mechanics, there are four types of motion. We have rotary, oscillating, linear and reciprocating motion. This motion helps to define the efficiency of production of machine wheels, axle and so on. i.e how effective they could be.
5. Level: This is the amount of place a liquid or substance is allowed to reach or stay in mostly container, or other object which can hold material. Application: Liquid level measurements are made to ascertain the quantity of liquid held in a container or vessel. This liquid affects both the container and the material used upon.
6. Pressure: Pressure means force per unit area exerted by a fluid on the suface of the container. Absolute pressure means the fluid pressure above the reference value of a perfect vacuum or the absolute zero pressure. Application: It is used in reciprocating compressors or engines, its usually used to convert it to displacement by an elastic element and then use one of the electromechanical transducers for an electrical output.
7. Flow: Flow measurement are essentially used for the transportation of slurries, compressed natural gas on pipelines, water and gas supply system to domestic consumers, irrigation systems and a number of industrial process controlled system.

What is viscosity

Viscosity: is defined as the resistance to flow. Resistance to flow means that the particles can move around, but it may be difficult for them to pass by each other. Viscosity decreases as the fluid is heated and increases as the fluid is cooled.

Advantages of viscosity in most industries

1. The viscosity of some medication such as the various fluids used to remove warts, has also been modified for easier application.
2. Drug companies manufacture medicines, such as cough syrup, that have a high viscosity yet are still drinkable, in order to coat and soothe the throat.
3. It is a measure of oil resistance to flow
4. It governs the sealing effect of oil and the rate of oil consumption.
5. It determines the ease with which the machines may be stated or operated under varying temperature conditions.

acceleration due to gravity= 9.81m/s²

Head= 300m

Efficiency rate= 75%

Velocity= 63000kg/s

P= ghrv

P = acceleration due to gravity × Head × Efficiency rate × Velocity

P = 9.81 × 300 ×

 × 63000

    =139,056,750

     = 140MN

1. It must maintain a stable voltage that does not range more than 10%
2. It must maintain a stable frequency that does not vary more than
3. It must be environmentally friendly: meaning that the lines should not cause traffic or inconvenient the people living in the immediate environment.
4. It must supply energy at an acceptable price.
5. It must provide at all times the power that consumers need.
6. It must meet or agree with safety standards.

(1) The measuring system of an indicating instrument is subjected to deflecting torque, controlling torque…………………….torque (1 mark)
Answer; the indicating instrument contains three types are (1)deflecting torque (2) controlling torque (3) damping torque
(2) Dynanometer wattmeter instrument is most commonly used ……………..
Answer; dynanometre are commonly used in AC and DC
(3) Moving iron instrument are either of attraction type or …………….
Answer; It is either of repulsion type or attraction type
(4) A ……………. Resistor extends the range of an ammeter
Answer; NOTE: THE RANGE OF PMMC AMMETER CAN BE EXTENDED BY CONNECTING A LOW RESISTANCE SHUNT IN PARALLEL, WHILE THE RANGE OF A VOLTMETER CAN BE EXTENDED BY CONNECTING A HIGH RESISTANCE CALLED MULTIPLIER IN SERIES.
(5) The digital instrument count the cycles produced by the unknown frequency during a precisely controlled…………….
Answer; period of time
(6) Define the term measuring instruments
ANSWER; MEASURING INSRUMENT ARE INSTRUMENT THAT ARE MAJORLY ELECTROMECHANICAL OR ELECTRONIC DEVICE, THAT IS USED TO MEASURE ELECTRICAL OR NON ELECTRICAL DEVICE IN ORDER TO DISPLAY THEIR QUANTITY EITHER IN A DICRETE FORM(USING DIGITAL INSTRUMENTS) OR VARYING FORM BY THE USE OF A POINTER (USING ANALOG INSTRUMENT)
c) List 5 advantages of electronic instrument over electromechanical instrument.
ANSWER
I) It is used to monitor nearby signal
ii) it’s not as enormous or big as compared to electromechanical instrument
iii) it has high flexibility
iv) it also have high sensitivity
v) low cost
vi) faster response when in use i. e during usage
d) Explain with the aid of an appropriate diagram and mathematical analysis that the deflecting torque of a permanent magnetic moving coil instrument (p.m. m. c) is proportional to the current flowing through it.
ANSWER
NOTE: Before showing the mathematical analysis you are expected to list all the parameters used in the p. m. m. C and their name. Such as;
B=breadth of the, coil in Meter
N=number of turns in the coil in turns
B=The flux density of the coil, in weber per meter
L=length of the depth of the coil in meter
I=current flowing through the coil in ampere

Followed by the solving… Such as;

The force magnitudeexperienced in the coil
F=BIL (BREADTH × CURRENT × LENGTH)
Number of turns experience at each side of the coil
F NBIL
Deflecting torque( Td) =F × distance at a right angle I.e BREADTH
Td= F×B I.e NBIL×B
A=L×B. so therefore,
Td=NBIA….. (1)
But we are asked to prove that deflecting torque (Td) is at right angle to the current flowing through. Then, we say
Constant (k) =NBA
Substitute NBA as K into equation
Td=KI
Recall, that anytime you have a quantity equal to constant (k) , with a value or parameter. It can be rewritten as the quantity DIRECTLY PROPORTIONAL TO THAT VALUE
So therefore,
Td is directly proportional to the current flowing through the coil
2) a Explain the construction and operation of a permanent magnetic moving coil instrument
ANSWER
This is based on the principle of operation that When an instrument is connected a circuit ;so as to measure voltage and current. A current pass through the coil due to the current being measured, which is then placed in the magnetic field of the permanent magnet which therefore allow a mechanical force to be exerted upon it. This allow the pointer on the moving system to be deflected in a clockwise way in the graduated scale, so as to indicate increase in current and voltage.
The deflecting torque on a permanent magnetic moving coil in a moving coil instrument, is as a result of the interaction between the field set up by a permanent magnet( this is reason it is called permanent magnetic moving coil).

ii) SYSTEMATIC ERROR :This error can be caused due to two factors
(a) Faulty instrument : this deals with the short coming of instrument
(b) Environmental factors: some instrument are affected by environmental condition which can lead to error.
iii) RANDOM ERROR : This are errors that can not be directly established. This means that the caused of the error is unknown because of random variation in the parameter or system of measurementmeasurement

2b) A moving coil instrument with a resistance of 10 ohms give a full scale deflection with a potential differene of 45mV. The coil has 100 turns, an effective depth of 3cm and a width of 2.5cm. The controlling torIque exerted by the spring is 49×10^-9NM. Calculate the density in the air gap
Solution
R=10ohms
TC=49×10^-9NM
P. d=45×10^-3 V
N=100turns
A=2.5×3×10^-4M=7.5×10^-4
B=?
I=V/R100
=45 ×10^-3/10
=4.5×10^-3A
At equilibrium Tc=Td
Tc=NBIA
49×10^-9=100×B×4.5×10^-3×7.5×10^-4
B=49×10^-9/3375×10^-7
B=49×10^-2/3375
=0.145×10^-3weber/M^2
2c) Highlights two merit and two demerit of pmmc
Two merit
I) They are accurate and reliable
ii) They have uniformly scale i.e evenly divided scale
Two demerit
I) it is limited to D. C only
ii) it is quite expensive compare to moving iron instrument because of their accurate design
3a) describe three types of error
I)GROSS ERROR :This deals majorly with human beings little mistake which can be caused by;
(a) IMPROPER ADJUSTMENT OF INSTRUMENT :Mostly when a laboratory personnel is trying to adjust the instrument to suit the measurements due to human errors some little mistake could take place which can later be ignored
(b) COMPUTATION ERROR:The operator may make mistake when putting the values in a written form
(c) CALCULATION ERROR:The operator might make mistake while calculating

3b) A voltmeter having a sensitivity of 100 ohm /V reads 100volts on it 150V scale when connected across an unknown resistor in series with milliameter when the milliameter reads 5mA, calculate
I) apparent resistance of the unknown resistor
ii) actual resistance of the unknown resistor
iii) Error due to loading effect of the voltmeter
SOLUTION
I) finding total resistance Rt=Vt/It
100/5×10^-3=20000ohms=20kohm
So therefore apparent resistance of the unknown resistor is 20Kohms

ii) voltage resistance =100×150=15000ohms(why is because we are given 100ohms per volts and 150v is given to represent one ohm)
Actual resistance =Rv×Rt/Rv-Rt
=150×20/150-20
=3000/130
=23.08Kohms

iii) % error =Actual -Apparent /Actual ×100
=23.08-20.0/23.0×100
=3.08/23.08×100
=13.34%

3c) Draw the major block diagram of a Cathode ray tube and explain each unit/stage

Cathode ray tube: it display the quantities being measured
Vertical amplifier :it amplify the signal waveform to be viewed
Trigger circuit : it produces trigger pulses to start horizontal sweep
Sweep generator :it produces saw tooth voltage waveform used for horizontal deflection to the electron beam
Horizontal amplifier: it is fed with a saw tooth voltage which is then applied to the x-plates
High and low voltage supply: it supply voltage power

4a) Highlights 4 advantages of digital frequency
i) The digital output signal can be coded as decimal BCD or binary codes
ii) digital frequency meter measures Unknown frequency by counting the number of cycles the frequency produce in a precisely contolled period of tim
iii) in a Schmitt trigger the signal is converted into square wave with a very fast rise and fall time than differentiated and chip.

EEC 126. CLASS: ND1

1. The measuring system of an indicating instrument is subjected to deflecting torque, controlling torque…………………….torque (1 mark) Answer; the indicating instrument contains three types are (1)deflecting torque (2) controlling torque (3) damping torque
2. Dynanometer wattmeter instrument is most commonly used ……………..Answer; dynanometre are commonly used in AC and DC
3. Moving iron instrument are either of attraction type or …………….Answer; It is either of repulsion type or attraction type
4. A ……………. Resistor extends the range of an ammeter Answer; NOTE: THE RANGE OF PMMC AMMETER CAN BE EXTENDED BY CONNECTING A LOW RESISTANCE SHUNT IN PARALLEL, WHILE THE RANGE OF A VOLTMETER CAN BE EXTENDED BY CONNECTING A HIGH RESISTANCE CALLED MULTIPLIER IN SERIES.
5. The digital instrument count the cycles produced by the unknown frequency during a precisely controlled…………… Answer; period of time
6. Define the term measuring instruments ANSWER; MEASURING INSRUMENT ARE INSTRUMENT THAT ARE MAJORLY ELECTROMECHANICAL OR ELECTRONIC DEVICE, THAT IS USED TO MEASURE ELECTRICAL OR NON ELECTRICAL DEVICE IN ORDER TO DISPLAY THEIR QUANTITY EITHER IN A DICRETE FORM(USING DIGITAL INSTRUMENTS) OR VARYING FORM BY THE USE OF A POINTER (USING ANALOG INSTRUMENT)

c) List 5 advantages of electronic instrument over electromechanical instrument.

ANSWER
I) It is used to monitor nearby signal
ii) it’s not as enormous or big as compared to electromechanical instrument
iii) it has high flexibility
iv) it also have high sensitivity
v) low cost
vi) faster response when in use i. e during usage

d) Explain with the aid of an appropriate diagram and mathematical analysis that the deflecting torque of a permanent magnetic moving coil instrument (p.m. m. c) is proportional to the current flowing through it.

ANSWER
NOTE: Before showing the mathematical analysis you are expected to list all the parameters used in the p. m. m. C and their name. Such as;
B=breadth of the, coil in Meter
N=number of turns in the coil in turns
B=The flux density of the coil, in weber per meter
L=length of the depth of the coil in meter
I=current flowing through the coil in amper

The force magnitudeexperienced in the coil
F=BIL (BREADTH × CURRENT × LENGTH)
Number of turns experience at each side of the coil
F NBIL
Deflecting torque( Td) =F × distance at a right angle I.e BREADTH
Td= F×B I.e NBIL×B
A=L×B. so therefore,
Td=NBIA….. (1)
But we are asked to prove that deflecting torque (Td) is at right angle to the current flowing through. Then, we say
Constant (k) =NBA
Substitute NBA as K into equation
Td=KI
Recall, that anytime you have a quantity equal to constant (k) , with a value or parameter. It can be rewritten as the quantity DIRECTLY PROPORTIONAL TO THAT VALUE
So therefore,
Td is directly proportional to the current flowing through the coil

Explain the construction and operation of a permanent magnetic moving coil instrument

ii) SYSTEMATIC ERROR :This error can be caused due to two factors
(a) Faulty instrument : this deals with the short coming of instrument
(b) Environmental factors: some instrument are affected by environmental condition which can lead to error.
iii) RANDOM ERROR : This are errors that can not be directly established. This means that the caused of the error is unknown because of random variation in the parameter or system of measurementmeasurement

2b) A moving coil instrument with a resistance of 10 ohms give a full scale deflection with a potential differene of 45mV. The coil has 100 turns, an effective depth of 3cm and a width of 2.5cm. The controlling torIque exerted by the spring is 49×10^-9NM. Calculate the density in the air gap

2c) Highlights two merit and two demerit of pmmc

3. Describe three types of error

3b) A voltmeter having a sensitivity of 100 ohm /V reads 100volts on it 150V scale when connected across an unknown resistor in series with milliameter when the milliameter reads 5mA, calculate
I) apparent resistance of the unknown resistor
ii) actual resistance of the unknown resistor
iii) Error due to loading effect of the voltmeter

Voltage resistance =100×150=15000ohms(why is because we are given 100ohms per volts and 150v is given to represent one ohm)
Actual resistance =Rv×Rt/Rv-Rt
=150×20/150-20
=3000/130
=23.08Kohms

iii) % error =Actual -Apparent /Actual ×100
=23.08-20.0/23.0×100
=3.08/23.08×100
=13.34%

3c) Draw the major block diagram of a Cathode ray tube and explain each unit/stag

1. Cathode ray tube: it display the quantities being measured
2. Vertical amplifier :it amplify the signal waveform to be viewed
3. Trigger circuit : it produces trigger pulses to start horizontal sweep
4. Sweep generator :it produces saw tooth voltage waveform used for horizontal deflection to the electron beam
5. Horizontal amplifier: it is fed with a saw tooth voltage which is then applied to the x-plates
6. High and low voltage supply: it supply voltage power

4a) Highlights 4 advantages of digital frequency

1. The digital output signal can be coded as decimal BCD or binary codes
2. Digital frequency meter measures Unknown frequency by counting the number of cycles the frequency produce in a precisely contolled period of tim
3. In a Schmitt trigger the signal is converted into square wave with a very fast rise and fall time than differentiated and chip.

CONTINUATION OF SUBNETS.
Example 1e: 255.255.128 [/25]Solution: Using class C network address 192.168.10.0 Since 128 is 10000000 in binary, here = 1bit for subnet and y = 7 bits for hosts.
192.1688.10.0 = Network address
255.255.255.128 = Subnet mask.

1. How many subnets?
   Since 128 is 1 bit on [10000000], the answer would be 2 = 2.
2. How many valid hosts per subnet? [Numbers of 2 bit]7 host bits off [10000000], 2 – 2 = 126 hosts.
3. What are the block sizes? 256 – 128 = 128
4. Write out the subnet address for each subnet.
   The number right before the value of the
   NO. 3 ANSWERS.
   = 128
   NO. 4 ANSWERS.
   Subnet 0.0 128.0
   First host 0.1 128.1
5. Broadcast Address for each subnet?
   Last host 127.254 255.254
   Broadcast 127.255 255.255
   ANSWER TO QUESTION 1e.
   i.) How many subnets can be produced from each mask?

Mask A = 255.255.255.128
128 = 10000000. So therefore, 128 has one bit on it 2^1 = 2 subnets.
Mask B = 255.255.255.192
192 has 2 bit on it 11000000
2^2 = 4 subnets
ii.) How many valid hosts per subnets are available?
For A = 2^7 – 2; = 128 – 2; = 126 valid host
B = 2^6 – 2; = 64 – 2; = 62 valid host
A = 7 bits off
B = 6 bits off
iii.) What is the block size of each mask?
For A = 256 – 128 = 128
B = 256 – 192 = 64
Increment for A is from 0, 128 but real subnetting values are 0.0, 128.0
Increment for B is from 0, 64, and 128
iv.) What are the valid hosts in each subnet?
ANSWER.
For A = 2^7 – 2 = 128 – 2 = 126
B = 2^6 – 2 = 64 – 2 = 62
v.) What is the broadcast address of each subnet?
ANSWER.
Broadcast address is always the number at the carrier after the subnet address
Subnet address: 126,252
What is digital transmission?
It is the physical transfer of data [a digital bit stream] over a point-to-point or point-to-multiple communication channel. Examples of such channels are copper wires, optical fibers, wireless, and communication channel and storage media. The data are represented as an electromagnetic signal, such as electrical voltage, radio wave, microwave, or infrared signal. It is the transfer of discrete messages. The messages are either represented by a sequence of fuist by means of line code.
3a.) Complete a table by listing every available subnet mask and its equivalent class inter domain routing [CIDR] slash notation starting from slash 8 [/8] to slash 30 [/30] [6 marks]SOLUTION.
SUBNET MASK.CIDR VALUE.255.0.0.0/8255.128.0.0/9255.192.0.0/10255.224.0.0/11255.240.0.0/12255.248.0.0/13255.252.0.0/14255.254.0.0/15255.255.0.0/16255.255.128.0/17255.255.192.0/18255.255.224.0/19255.255.240.0/20255.255.248.0/21255.255.252.0/22255.255.254.0/23255.255.255.0/24255.255.255.128/25255.255.255.192/26255.255.255.224/27255.255.255.240/28255.255.255.245/29255.255.255.252/30
What is subnet mask?
It is a 32 bit value that allows the recipient of JP packets of distinguishing the network ID portion of the IP address from the host ID portion of the IP address.
What is CIDR [Classic Inter-domain Routine]?
This can be define as the method or ways in which ISP [Internet Service Provider] allocate or distribute a number of address to house, office etc.

COMPUTER PROTOCOL.
This can be defined as a standard program develop to enhance method of transmitting and processing of various kinds of information from one device to another either by wired or wireless.

TYPES OF PROTOCOL.
(1) TCP/IP
Transmission Control Protocol: this involves way of creating a packet and putting them in direct order and checking that no packet got loss at the transmission.
(2) IP: it is a means to channel information to the proper address.
(3) VDP/ICMP
(I) VDP: It is use with the IP when small amount of information involved.
(ii) ICMP: It is use for diagnosis and management purpose for small messages.
(4) Interactive Mail Access Protocol [IMAP]: It allows reading of individual mail box at a single account and commonly business environments.
(5)HTTP [Hyper Text Transfer Protocol]

Question six (6) 2018/2019
Answer:
(1) Proximity to raw materials. E.g the sitting of hydro station is determined by natural water power source.

(2) Proximity to load center: There are factors like resistance that can deteriorate how effective the electricity will flow, due to the closeness or how distant it’s from the transformer

(3) Technical factors. At this point we are going to be talking about the operational factors. Getting spare parts and skilled professional technician to operate the transformer is also needed.
(4)Economic factors.in the managing and maintenance of the transformer is also included.
(5) Environmental factors. Due to the environment it’s been situated also matters a lot. For example a transformer which is situated in a cool environment will function properly, than a transformer situated in an unfriendly environment.

Calculate the power generated by a station which has a heed of 300m a flow rate of 6300kg/s and an overall efficiency of 75%.

Solution
P = ghr
H = 300m
Velocity, V = 6300
= , g = 9.8m/s
P = ghrV
= 9.81 x 300 x x 6300
But to convert it to newton:
11371752 you get to had one 0 (zero) to the numbers
113, 717,520
= 114MN

Power II
(A) Obtain the ABCE parameters for a medium transmission line using nominal –π network.
(B) List four (4) parameters that determine the performance of a transmission line.
Answers
Where A, B, C and D are the constants known as ‘generalized circuit constants’ of the transmission line. Their valves depend on the particular method adopted for solving the transmission network line.
Short line: in the case of lines up to 50 Km, the effect of capacitance on the line performance is negligible. Hence, here, Ls = LR and Vs – VR + LRZ
Comparing this with equation (i) and (ii) above, we get that A = 1, B = 2, C = 0 and D = 1
Incidentally it may be noted that AD – BC = 1
Medium line –nominal –T method
Vs = V1 + Is 2/2
Vi = VR + IR 2/2
Ic = Is – IR = ViY = Y[i/r + IR Z/2] Is = V2Y + In[ Is + YZ/2] Eliminating Vi from equation (iii) and (iv), we get:
Vs = VR + +
Substituting the value of Is, we get:
Vs = [ I + ] VR + [ 2 + [ 2 + Y22/4] IR
Comparing equation (iv) and (v) with equation (I) and (ii) respectively, it is found that:
A = D = I + ; B = [ I + ] and C = Y
It can again be proved that AD – BC = 1
Medium line _nominal π method.
Series impedance per phase = [ R + sx] And admittance is Y = jwc
As seen Is = 1 + ICL = I + VS Y/2
I = IC1 + IR = IR + VRY/2
VS = VR + IZ = VR + Z [ IR + VRY/2
= [ I + Y2/2 ] VR + 2IR
Eliminating I from equation (vii) and (x), we get:
Is = IR + VRY/2 + VSY/2
Now substituting the value of Vs, we have:
Is = IR + VRY/2 + Y/2 { [I + Yz/2] VR + ZIR }
Is = Y[ I + Yz/4] VR + [ I + Yz/2] IR
Comparing equation (x) and (ii) with equation (i) and (xi) above, we get:
A = D = [ I + Yz/2] ; B = Z, C = Y [ I + Yz/4] Again it can be shown that AD – BC = 1

(B)
State four (4) advantages of underground cables.
Answer:
Cables lay underground is very important because due to very small spacing of their conductors, they have a very slow inductance and hence, low inductive drops.
They are good for feeders which are not likely to be disturbed for tapping purposes.

You can also check relative topics below

What is JFET?

A JFET consists of a p-type or n-type silicon bar containing two pn junctions at the sides as shown in the Figure below. The bar forms the conducting channel for the charge carriers. If the bar is of n-type, it is called n-channel JFET and if the bar is of p-type, it is called a p-channel JFET. The two pn junctions forming diodes are connected internally and a common terminal called gate is taken out. Other terminals are source and drain taken out from the bar. Thus a JFET has essentially three terminals which are gate (G), source (S) and drain (D)

Principle of Operation Of JFET

When a voltage VGS is applied between drain & source terminals and Vas is zero, the two p-n junction at the sides of the bar establish depletion layers. The electrons will flow from source to drain through a channel between the depletion layers. The size of these layers determine the width of the channel and hence the current conduct through the bar.

Principle of Operation Of JFET

IMPORTANCE CHARACTERISTICS OF JFET

Hiigher input impedance
Generate less noise
High resistance to nuclear radiation

It is a 3-terminal device terminal voltage controlled semiconductor device i.e. input voltage controls the output characteristicIt is always operated with Vas p-n junction reversed biased.
Gate current, IG = 0A. Hence ID = IS.
JFET is not subject to thermal runaway when the temperature of the device increase
The drain current ID is controlled by changing the channel width
No β rating for JFET because of since IG = 0

There are basically two types of transistors
Bipolar junction transistor (BJT) :- a current controlled device in which output characteristics are controlled by base current
Field effect transistor (FET) :- output characteristics controlled by input voltage i.e. electric field
Types of FET
1. Junction Field Effect Transistor (JFET)
2. Metal oxide semiconductor Field Effect Transistor (MOSFET)
The two types of transistor differ in both their operating characteristics and their internal construction.
BJT is so called because both holes and electrons plays part in the conduction process

Principal Disadvantages Of The BJT

Difference Between JFET and BJT

1. Only one type of carrier, holes in p – type channel and electron in n- type channel in JFET WHILE electron and holes takes part in conduction in BJT
2. JFET has high input impedance since the input circuit is reversed biased WHILE input circuit for BJT is forward biased hence it has low input impedance
3. No current enters gate of JFET i.e. IG = 0 WHILE BJT base current is of few µA
4. JFET uses voltage applied on gate to control current between drain and source WHILE BJT uses current applied to base to control a large current between the collector and the emitter
5. In JFET there is no junction as in BJT. Conduction through an n –type or p – type semi conductor material for this reason noise level in BJT is very small

WIDE AREA NETWORK

WAN]:Wide area networking combines multiple LANs that are geographically separate. This is accomplished by connecting the different LANs using services such as dedicated leased phone lines, dial-up phone line (both synchronous and asynchronous), satellite link, and data packet carrier services. It can be as simple as a modem and remote access server for employees to dial into, or it can be as complex using special routing protocols and filters to minimize the expense of sending data sent over vast distances.

METROPOLITAN AREA NETWORK

MAN consists of a computer network across an entire city college campus or small region. A MAN is larger than a LAN. Depending on the configuration, this type of network can cover an area from miles to tens of miles. A MAN is often used to convert several LANs together to form a bigger network. It is specifically designed for security purpose.

VIRTUAL PRIVATE Network

[VPN]: VPN is a technology that allows a network administrator to create a secure connection over a loss-secure network between computer and the internet. It protects information privacy by allowing the administrator to anonymously appear to be in any network. A VPN is beneficial because it guarantees an appropriate level of security and privacy to the connected systems. This is extremely useful when the existing network infrastructure alone cannot support it.

         EEC 124

Past question and answer

Answer all

1) Describe the basic principle of operation of a bipolar junction transistor including me why majority carriers crossing into the base from the emitter pass to the collector and why the collector current is nearly equals to the emitter current.

Answer
Don’t panick when you see a question like this in the exam hall. This is what you just have to do…. And guess, you just have to answer it step by step..,.. As simple as that.
So let’s go..

BASIC PRINCIPLE OF A BIPOLAR TRANSISTOR

Firstly, a bipolar transistor consists of both NPN and PNP transistor. It also have an N part and a P type material.
After then draw both PNP and NPN junction transistor

It has three layers, three terminal and two junction
-The emitter is heavily doped in a bipolar transistor in order to carry charge carriers from it region to the base region. The charge carriers here are called majority charge carrier while the few charge carriers are called minority(in a PNP junction transistor the emitter is heavily doped so as to pass holes to the base while in a NPN transistor it is heavily doped and forward biased so as to pass electrons to the base region. It contains majority charge carrier

-the base region at the middle is moderately doped so as to be able to control the charge carriers coming from the emitter to the collector. Only 0.5% of charge carriers coming from the emitter remain in the base region why 99.5% is found in the collector. The base region contains minority charge carriers. (For PNP transistor electrons are the minority charge carriers here,, while in NPN transistor the holes are the minority charge carriers.)

-the collector is lightly doped so as to be able to receive charge carriers controlled by the base region. It also contain majority charge carriers.
This will help you to understand,
( Take the expression as a cup which is filled, assuming you fill it with an emitter, may be tap water. Then you use your hand to control it to another cup, which must be empty in other to receive water from the filled cup. At the end you will observe that, the filled cup controlled to the empty cup, still have small water)

Second question says, why majority carriers crossing the base from the emitter region to the collector region.
ANSWER: Because the base is forward bias and heavily doped to pass majority carrier to the base. And the Base is moderately doped so that majority carrier crossing the base may be controlled to the collector which is lightly doped to receive majority carriers from the base.

Third question says, why is collector current nearly equals to the emitter current
Answer G
The question has been answered from the previous page sn’t it?

Because out of 100% of charge carriers coming only 0.5%are left in the base while 95.5% are found in the collector region
These expression makes the collector current approximate to the emitter current.
NOTE. Majority carriers are found in the emitter and collector region while minority carriers are found in the base region.

b) The application of an external voltage to a PN junction diode can influence the drift of holes and electrons. With the aid of a diagram explain this statement, and also how the direction and magnitude of the applied voltage affect the depletion layer.
ANSWER

When an external voltage is applied to a p-n junction making the p-type material positive with respect to the n-type material, as shown in the p-n junction is forward biased.The applied voltage opposes the contact potential, and in effect, closes the depletion layer. Holes and electrons can now cross the junction and current will flow.

An increase in the applied voltage above is required to narrow the depletion layer about 0.2V for germanium and 0.6V for silicon, as a result rapid rise in the current flow. Graphs depicting the current-voltage relationship for forward bias pn junction.

When an external voltage is applied to a P-N junction making the p-type material negative with respect to the n-type material the p-n junction is reversed bias. The application voltage is now in the same sense with the contact potential and opposes the movement of holes and electron due to opening up the depletion layer.
Thus in theory, no current flows. However at normal room temperature certain electrons in the covalent bond lattice acquire sufficient energy from the heat available to leave the lattice, generating mobile electrons and holes. This process is called the electron hole generation by thermal excitation are called minority carrier and this will be attracted by the applied voltage. Thus, In practice, a small current of few micro amperes for germanium and less than one micro amperes for silicon, at normal room temperature, flows under, reverse bias condition.
As the magnitude of the reverse voltage is increased a point is reached where a large current suddenly start to flow. The voltage at which this occur is called the breakdown voltage

c) A pure piece of silicon is doped with (I) pentavalent impurity and (ii) trivalent impurity. Explain the effect this have on the form of conduction.

Answer
Arsenic, antimony and phosphorus have five valence electrons (pentavalent) and when a semiconductor such as silicon is doped with one of these substance, some impurity atoms are incorporated in the tetrahedral structure resulting in N- type material. The fifth valence electrons is not rigidly bonded and is free to conduct, the impurity Atom donates a charge carrier. The resulting material is called n-type material.
It has an excess conduction: This means that the resulting n-type material contain free electro

indium, aluminum and boron have three valence electrons and when a semiconductor such as silicon is doped with one of these substance, some if the semiconductor atoms are replaced by semiconductor impurity resulting into P-type semiconductor. One of the four bond associated with the semiconductor material is deficient by one electron and this deficiency is called a Hole.
It has a deficit conduction: This is when holes give rise to conduction when it capture free electron from neighboring atom.

d) Explain with the aid of a suitable diagram the three states of a scr (silicon controlled rectifier)

Answer
The scr has three conducting state
1) forward blocking state: The anode is positive with respect to the cathode
-J1 is forward biased I.e it is on
-j2 is reversed bias. I.e it is off
-J3 forward biased i.e it is on

• The gate is not triggered
  Therefore scr is not on

2)reverse blocking state: The anode is negative with respect to the cathode.
-J1 is reverse biased I.e it is off
-j2 is forward biased. I.e it is on
-J3. reverse biased i.e it is off
-The gate is not triggered
Therefore the scr is not on

3)forward conducting state:The anode is positive with respect to the cathode.
J1 is forward biased I.e it is on
-j2 is forward biased. I.e it is on
-J3 forward biased i.e it is on

• The gate us triggered
  So, therefore scr is on.

Question 2) Draw the circuit for CC, CB and CE configuration of pnp bipolar transistor, showing correct polarities and direction of various current.
Answer
Current gain =

2b) A bipolar junction transistor operate with a collector current of 1.2A and a base collector of 50mA. What will be the value of the emitter current be.

Answer
From kirchoff’s law when viewing a common base, one will derive that
IE=IB+IC
when, IB=0.05A, IC=1.2A
IE=0.05A + 1.2A.
=1.25A

2c) Explain why the emitter region of a bipolar junction is heavily doped.

Answer
Emitter region is always heavily doped so as to carry or supply enough charge carriers such as electrons and holes to cross the base to the collector region.

3a) Explain briefly the action of a pn junction(I)on open circuit(no external voltage) (ii) when provided with a forward biased (iii) when provided with a reversed biased. Draw the characteristics graph for a forward biased and reversed biased condition.

Answer
When it is open circuited.
We assume that separate block of p-type and n-type materials are pushed together. Also assume that a hole is positive charge carrier at the junction the donated electrons in the n-type material, called the majority carrier diffuse into the p-type material (diffusion is from an area of high density to an area of lower density) and the acceptors hole in the p-type material diffuse into the n-type material. Because the n-type material has lost electrons, it acquires a positive potential with respect to the p-type material and thus tends to prevent further movement of electrons. The p-type material has gained electrons and becomes negatively charge with respect to the n-type materials and hence tends to retain holes. Thus after a short while, the movement of electrons and holes stop due to potential difference across the junction, called the potential barrier. The area in the region on the junction becomes depleted of holes and electron due to electron-hole recombination called depletion layer
Meaning of some terms used
Diffusion:mobile holes move from the n-type material to the p-type material.

When an external voltage is applied to a p-n junction making the p-type material positive with respect to the n-type material, as shown in the p-n junction is forward biased.The applied voltage opposes the contact potential, and in effect, closes the depletion layer. Holes and electrons can now cross the junction and current will flow.

An increase in the applied voltage above is required to narrow the depletion layer about 0.2V for germanium and 0.6V for silicon, as a result rapid rise in the current flow. Graph depicting the current-voltage relationship for forward bias pn junction.

When an external voltage is applied to a P-N junction making the p-type material negative with respect to the n-type material the p-n junction is reversed bias. The application voltage is now in the same sense with the contact potential and opposes the movement of holes and electron due to opening up the depletion layer.

3b) Explain zener and avalanche breakdown.

Answer
Zener breakdown :this form of breakdown occurs in heavily doped junctions thereby narrowing the depletion layer. The breakdown voltage set up a strong electric field (about 108 V/M) across the depletion layer. This electric field is strong enough to break or rupture the covalent bonds thereby generating electron-holes pairs, even a small increase in reverse voltage will result in large current flow, therefore after the breakdown voltage is reached the resistance drops markedly. It occurs at a voltage less than 6ev.
iii) Avalanche breakdown :this form of breakdown occurs in lightly doped junction thereby having a wide depletion layer where the electric field is not strong enough for zener breakdown to occur instead the minority carriers (accelerated by the field) break the covalent bond.A relatively large current flow once the avalanche point is reached. For avalanche this voltage always occur at a voltage above 6ev.

4a) Discuss intensively extrinsic and intrinsic semiconductors.

Answer
INTRINSIC(PURE)SEMICONDUCTOR: This is the semiconductor material in a pure form silicon or germanium with no doping atoms added are called intrinsic semiconductors. At room temperature, some of the electrons acquire sufficient energy for them in o break the covalent bond between atoms and become free mobile electrons. This is called thermal generation of electron-hole pairs. Electrons generated thermally create a gap in the crystal structure called hole, the atom associated with the hole positively charged, since it has lost an electron.This positive charge may attract another electron released from another atom, creating a hole elsewhere.
When a potential is applied across the semiconductor material, holes drift towards the negative terminal (unlike charges attract), and electrons towards the positive terminal, and hence a small current flows.

Extrinsic (impure) semiconductor: when a suitable impurity is added to a semiconductor;its current conducting property changes appreciably and this process of adding an impurity is doping and the added impurity is called a dopant. Adding extremely small amounts of impurities to pure semiconductors in a controlled manner is called doping.
N type semiconductor
Antimony, arsenic and phosphorus are called n-type impurities because they donate electrons. A material is said to be n type semiconductor when an impurity like antimony, arsenic and phosphorus are added to a pure semiconductor such as silicon.

Arsenic, antimony and phosphorus have five valence electrons (pentavalent) and when a semiconductor such as silicon is doped with one of these substance, some impurity atoms are incorporated in the tetrahedral structure resulting in N- type material. The fifth valence electrons is not rigidly bonded and is free to conduct, the impurity Atom donates a charge carrier. The resulting material is called n-type material.
It has an excess conduction: This means that the resulting n-type material contain free electro
P type semiconductor
indium, aluminum and boron have three valence electrons and when a semiconductor such as silicon is doped with one of these substance, some if the semiconductor atoms are replaced by semiconductor impurity resulting into P-type semiconductor.One of the four bond associated with the semiconductor material is deficient by one electron and this deficiency is called a Hole.
It has a deficit conduction: This is when holes give rise to conduction when it capture free electron from neighboring atom.

b) Explain what is meant by linkage current in a bipolar junction transistor and why this can be usually ignored.

Answer
Linkage current is the current which is produce by the result of minority charge carriers. And minority charge carriers are caused by few charge(electrons and holes) in a reversed current.
It is usually ignored because it is very small as a result of the minority charge carriers and hereby it is ignored.

C) state four application of the transistor.

. answer
A. It is used as detector
B. It is used as amplifier
C. It is used as motor rectifier
D. It is used as oscillator

5) in a tabular form differentiate between the three transfiguration terms of input resistance, output resistance, current gain and voltage gain.
Answer

5b) Draw the circuit symbol and give one(1) application of SCR, varactor diode, schottky diode and light emitting diode.
Answer
Application of SCR
(1) Used for switching an A.C power control.

Application of varactor diode
(1)

Application of schottky diode
(1)used for the construction of an integrated circuit design for high speed digital logic application.

Application of light emitting diode
(1)it is used as an indicator

6a) using well labelled diagram show the crystal lattice of intrinsic semiconductor and N type semiconductor and P type semiconductor.

Answer
When additional mobile electrons are introduce by doping a semiconductor with pentavalent atom i.e N type semiconductor these mobile electrons are called majority charge carriers while the relatively few holes produce as a result of intrinsic action in the semiconductor.
For P type semiconductor, the additional holes are introduced by doping a trivalent atom. The holes are called majority carriers while the relatively few electrons in the p type material as a result of intrinsic action are called minority charge carriers.
IN SUMMARY,
majority carriers in N type semiconductor are mobile electrons while minority charge carriers are holes.
IN P TYPE majority charge carriers are holes while minority charge carriers are electrons.
NOTE:Majority charge carriers are charge carriers that are dominating or well sufficient in that element why minority charge carriers are charge carriers that are few i.e not sufficient, very few.

6b) Explain majority and minority charge carriers as regard to extrinsic semiconductor.