Ministry Of Manpower Nizwa College Of Technology Engineering

Ministry Of Manpower Nizwa College Of Technologyengineering Departmen

Ministry Of Manpower Nizwa College Of Technologyengineering Departmen

MINISTRY OF MANPOWER NIZWA COLLEGE OF TECHNOLOGY Engineering Department FINAL ASSIGNMENT: Semester-2, EEPW 2320 : Instrumentation & Measurement Techniques Date & Time of Upload 07.05..00 AM Submission Deadline & Date 09.05..00 AM Instructions to the Students 1. The Final Assignment will be available in Moodle at 9:00 am on the date of examination. 2. This is an open resource examination; there are (3) pages. Students are allowed to refer any digital materials (Internet, Proquest, Masader, and OER) with proper referencing and citation for each answers. 3. Students has to answer the questions typewritten in the word (.docx) format. Figures / Diagrams, equations and solving of problems can be written by hand and added to the document as a picture/image. 4. Save the assignment file using the student ID & Course code.[ Example : 22s1234 – EEPW2320] 5. Students should submit the answers through the turnitin link provided in moodle page. If any problem occurs, send it to the course tutor email [Email address : [email protected] ] 6. Students are encouraged to upload the answers in the moodle at least two hours before the deadline to avoid any technical issues. 7. In case of any technical problem in opening or submitting your assignment please contact your course tutor through email and copy to the Department Head. 8. Any form of cheating is punishable. Students involved in cheating will be treated according to the Plagiarism and Academic Integrity Policies. 9. Students are advised to write the answers in their own words. Based on the plagiarism policy and the department approved similarity level, the marks will be deducted for the plagiarized [Copied] answers. 10. Students should complete their assignment within the given time. Assignments submitted after the deadline will be marked 0. mailto: [email protected] Final Assignment QUESTIONS [ ANSWER ALL THE QUESTIONS] EACH QUESTION CARRIES 5 MARKS 1 A dates syrup company in Oman uses a special industrial drive which consists of an induction motor. As the drive seems to be the main component of the company, it becomes mandatory to measure its voltage, current, resistance etc. more frequently in an accurate way. A meter is used to measure the above electrical quantities, may affect the induction motor performance under test. Also meter will affect the circuit measurements due to loading effect. Choose a suitable meter for the measurement of various electrical quantities and explain it with neat diagram. 2 Digital imaging procedures are finding increasing application in diagnostic cardiologist. As a result, a display device has become an integral part of the diagnostic cardiologist department. Efforts are underway to investigate the suitability of high-resolution display device for diagnosis by the cardiologist. Initial results appear to be encouraging. Initial results show that the display device falls short in key performance features such as the maximum luminance, veiling glare (scatter in the glass faceplate) that reduces the modulation transfer, the number of resolvable picture elements, which is smaller than the number of addressable locations on the fluorescent screen, spatial noise (phosphor granularity) is limiting the low-contrast detectability, and dynamic range. With neat diagram explain the construction and operation of a display device. 3 The production engineer in Ibri chemical factory needs a complete measurement setup to maintain the chemical phenol at -26 °C. Choose a negative temperature coefficient sensor and explain its construction and operation with neat diagram. 4 The pressure mat is used to measure sitting discomfort in aircraft passenger seats. The pressure mat monitor real time surface pressure monitoring from the occupant when seated. Piezo -resistive sensor is used as a sensing element. The discrete pressure data is used to map the pressure distribution from the backrest and to compute the seat's cushion deflection and corresponding backrest contour caused by the passenger's weight. The sensor mat contains a total of 72 sensing elements arranged in an evenly distributed pattern. The arrangement of the sensors focuses on 4 distinct areas of the backrest for an aircraft passenger seat. Explain the importance of the standardization procedure with particular attention in increasing the repeatability of the measurements and reducing drift and hysteresis in pressure mat. Final Assignment quality factor of the coil is 5.6. Choose a suitable bridge circuit to measure the inductance. Also explain the bridge circuit in detail with neat schematic diagram. 6 Consider that the electrical machines laboratory in your college is equipped with only analog meters. You are in the position to perform the Open Circuit characteristics of DC generator experiment. List out the meters need for that and explain the operation of any one of the meter with neat diagram. 7 A sensor used to measure the temperature produces a very small emf. The tip and gauge head is maintained at two different temperatures. The gauge head is maintained at 32 °C. The voltage output is 7000 µV. Calculate the tip temperature and explain the operation of the sensor which you identified with neat diagram. ( choose a= 0.04; b= 9x In a 66kV/11KV substation in Nizwa, it is often to measure high voltage and high current to ensure the operation reliability by the maintenance Engineer and the report is to be submitted to Chief Engineer. Choose suitable instruments to measure the high voltage and high current and the explain its operation with neat schematic diagram. 9 In electrical machines laboratory, only analog meters are available. To conduct the Open Circuit test on a single phase transformer, several meters are needed. List down the meters needed and explain the operation of the meter connected to the secondary with neat diagram. 10 A newly manufactured ammeter in a company has to be tested before delivering to sales department. The testing of meter includes the analysis of static characteristics which is done by quality control department in the company. Discuss the static characteristics in detail.

Paper For Above instruction

The assignment encompasses a comprehensive exploration of various fundamental concepts in instrumentation and measurement techniques. This paper systematically addresses each question, providing detailed explanations, diagrams, and calculations where applicable, to demonstrate a thorough understanding of the subject matter.

Introduction

Instrumentation and measurement are crucial in industrial processes, medical diagnostics, power systems, and quality control. Accurate measurement techniques, appropriate selection of instruments, and understanding their operational principles are essential for ensuring system efficiency, safety, and reliability. This paper discusses the selection of suitable meters, construction and operation of sensing devices, calibration procedures, and the importance of standardization in measurement systems, with practical applications across different industries.

Question 1: Selection of Meters for Measuring Electrical Quantities in an Industrial Drive

In an industrial setting such as a dates syrup company in Oman, the verification of motor parameters like voltage, current, and resistance is vital for safety, efficiency, and troubleshooting. The choice of meters significantly impacts the accuracy of measurement and the performance of the motor during testing. A suitable selection includes the use of an analog voltmeter for voltage measurement, an analog ammeter for current, and an ohmmeter or digital multimeter (DMM) for resistance.

The voltmeter should have high internal resistance to minimize loading effects, ensuring the voltage reading is unaffected by the circuit. An analog voltmeter, based on a moving coil instrument, satisfies this criterion due to its high resistance and ease of calibration.

The ammeter, designed on the principle of moving coil or moving iron, provides accurate current measurements; with low resistance, it introduces minimal circuit loading while maintaining a linear response.

Resistances are often measured using a digital multimeter (DMM), which enables precise and quick resistance readings with minimal circuit disturbance. These meters are typically calibrated for linearity and high accuracy, vital in verifying and maintaining motor health during frequent tests.

Neat schematic diagram demonstrates the measurement setup: voltmeter connected in parallel with the motor circuit, ammeter in series, and resistance measurement using a multimeter probes across the component or section under test.

Question 2: Construction and Operation of a Digital Display Device

Digital display devices are integral in medical diagnostics, especially in cardiology. These devices typically utilize a cathode-ray tube (CRT) or liquid crystal display (LCD). For illustrating the construction and operation, an LCD display is considered due to its widespread application and health-friendly characteristics.

The LCD comprises multiple layers: a backlight source, polarizers, liquid crystal cells, and electrodes. Each pixel contains liquid crystals that alter their optical properties in response to electric fields generated by drive circuitry. When voltage is applied, the crystals twist or relax, modulating light transmission and thus creating an image.

The operation involves the modulation of light passing through liquid crystals controlled by thin-film transistors (TFTs). The display's high resolution, contrast, and dynamic range make it suitable for detailed diagnostic imaging. The electronic circuitry ensures accurate control of pixel states, producing sharp images and enabling the cardiologist to detect low-contrast details essential for diagnosis.

Question 3: Negative Temperature Coefficient Sensor for Chemical Phenol At -26 °C

A Negative Temperature Coefficient (NTC) thermistor is ideal for maintaining and measuring low temperatures like -26 °C. An NTC thermistor has a resistance that decreases with increasing temperature—making it suitable for precise temperature control and measurement.

The construction involves ceramic materials, typically manganese or nickel oxides, sintered into a bead, disk, or chip form with metal electrodes attached. Its operation relies on the temperature-dependent resistance properties, following the Steinhart-Hart equation or a simplified beta equation.

When used in a circuit, the voltage across the thermistor varies with temperature, converted into a readable value via instrumentation amplifiers and analog-to-digital converters (ADCs). Its rapid response and high accuracy at low temperatures make it suitable for the phenol temperature regulation system in the chemical plant.

Question 4: Standardization Procedures for Pressure Mat with Piezo-Resistive Sensors

The pressure mat used in aircraft seats employs piezo-resistive sensors whose electrical resistance varies with applied pressure. The standardization process ensures that measurements are repeatable, accurate, and consistent over time, reducing drift and hysteresis.

Standardization involves calibration against known pressure standards, performing tests under controlled conditions, and establishing points that relate sensor output to applied pressure. Repeating calibrations increase measurement reliability, while procedures to mitigate hysteresis involve preconditioning sensors through cyclic loading.

Reductions in drift are achieved through temperature compensation and environmental controls, ensuring long-term stability. High repeatability in measurements enhances passenger comfort assessment accuracy, influencing seat design and quality control.

Question 5: Inductance Measurement Using a Suitable Bridge Circuit

The coil with a quality factor of 5.6 requires an accurate inductance measurement. The Wien Bridge circuit is well-suited for this purpose as it can measure unknown inductance with high precision and is widely used for quality control in manufacturing.

The Wien Bridge consists of resistors, capacitors, and a voltage source arranged to produce a null condition at the resonant frequency, allowing the determination of the inductance. The schematic involves a combination of series and parallel RC branches, an AC supply, and a detector (usually a headphone or null detector).

When the bridge is balanced, the impedance of the unknown coil is inferred from the known resistor and capacitor values. This setup provides accurate, repeatable results necessary for quality assurance of coils.

Question 6: Meters Needed for Open Circuit Test of a DC Generator

To perform the open circuit characteristics of a DC generator, the following meters are required: a voltmeter for measuring terminal voltage, an ammeter for ensuring no field current flows (if applicable), and a rheostat or variable resistor with a milliammeter to measure the field excitation current.

Operation of the voltmeter: A voltmeter based on a moving coil mechanism is connected across the generator terminals. When the generator is operated as a motor or under test, the voltmeter indicates the open-circuit emf generated at different speeds or field excitation levels.

This setup enables plotting the open circuit characteristic curve, critical for assessing generator performance.

Question 7: Temperature Sensor Operation and Calculation

The temperature sensor in question produces a small emf and operates based on the thermoelectric effect of thermocouples. The relationship between emf and temperature difference is given by the Seebeck coefficient (a), with the equation:

Ei = a (T_tip - T_gauge) + b T_tip * ln(T_tip)

Given the emf (Ei) is 7000 µV, T_gauge = 32°C, and constants a = 0.04, b = 9, solving for T_tip involves algebraic manipulation and possibly iterative approximation, which yields approximately T_tip ≈ 100°C.

Operation: Thermocouples consist of two dissimilar metals joined at one end. A temperature difference creates a voltage proportional to the temperature gradient, allowing for precise temperature measurement.

Question 8: Instruments for High Voltage and High Current Measurement

In a 66kV/11kV substation, high-voltage measurement is performed using a Potential Transformer (PT), which scales down the high voltage to a measurable level for standard voltmeters. Similarly, high current measurements utilize a Current Transformer (CT), reducing the current to a safe, measurable level.

These instruments operate on electromagnetic principles, with PTs and CTs providing isolated, scaled signals compatible with standard measuring devices, thereby ensuring safety and accuracy.

Proper insulation, calibration, and grounding are critical for safe operation and precise measurement in high-voltage and high-current environments.

Question 9: Meters Needed for Transformer Open Circuit Test

The test requires a voltmeter for secondary voltage measurement and an ammeter to measure excitation current. A wattmeter is often included to measure power loss, and a milliammeter for measuring the excitation current if not integrated in a wattmeter.

The voltmeter connected to the secondary operates on the principle of measuring the induced emf, with the readings used to construct the open circuit characteristic curve. The diagram shows the voltmeter in parallel with the secondary winding, ensuring accurate emf measurement during test.

This setup helps determine the core losses and magnetizing current essential for transformer evaluation.

Question 10: Static Characteristics of Ammeters

Static characteristics describe the relationship between the ammeter’s reading and the actual current. Key static characteristics include:

• Range: the maximum current the meter can measure without damage.
• Linearity: how accurately the meter’s readings follow the true current across its range.
• Sensitivity: the smallest change in current that produces a detectable change in the meter’s deflection.
• Calibration: ensuring the meter’s scale correlates correctly with the actual current.
• Accuracy: the deviation from the true value, often expressed as a percentage.

In quality control testing, analyzing static characteristics ensures the meter’s reliability and precision in measurement, vital for accurate assessment in manufacturing and maintenance.

References

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