EMTC 111 Electrical/Electronic Measuring Instruments Module II PDF

EMTC 111 – Electrical/Electronic Measuring Instruments MODULE II 9 September 2024 Page 1 Module II: Types of Electrical Instruments Lesson 1: Direct Current (DC) and Alternating Current (AC) Measurements Lesson 2: Moving Coil Instruments Lesson 3: Moving Iron and Electrodynamic In...

EMTC 111 – Electrical/Electronic Measuring Instruments MODULE II 9 September 2024 Page 1 Module II: Types of Electrical Instruments Lesson 1: Direct Current (DC) and Alternating Current (AC) Measurements Lesson 2: Moving Coil Instruments Lesson 3: Moving Iron and Electrodynamic Instruments Lesson 4: Ohmmeter, Ammeter, Voltmeter, and Wattmeter 9 September 2024 Page 2 Module II, Lesson 1: Direct Current (DC) and Alternating Current (AC) Measurements EMTC 111 – Electrical/Electronic Measuring Instruments 9 September 2024 Page 3 Module II, Lesson 1: Direct Current (DC) and Alternating Current (AC) Measurements Objective: To understand the fundamental differences between direct current (DC) and alternating current (AC), including their characteristics, applications, and measurement techniques. This lesson will also cover the advantages and disadvantages of both types of current. 9 September 2024 Page 4 Module II, Lesson 1: Direct Current (DC) and Alternating Current (AC) Measurements Topics Covered: 1. Introduction to Direct Current (DC) 2. Introduction to Alternating Current (AC) 3. Comparison of DC and AC 4. Applications of DC and AC 5. Measurement Techniques for DC and AC 9 September 2024 Page 5 Module II, Lesson 1: Direct Current (DC) and Alternating Current (AC) Measurements 1. Introduction to Direct Current (DC) 1.1 Definition and Characteristics Definition: Direct Current (DC) is the type of electrical current that flows in a constant direction. The voltage level remains constant over time. Characteristics: Unidirectional Flow: Current flows in one direction, from the positive to the negative terminal. Constant Voltage: The voltage remains stable, not fluctuating or changing polarity. Examples: Batteries, DC power supplies, and electronic devices like smartphones and laptops. 9 September 2024 Page 6 Module II, Lesson 1: Direct Current (DC) and Alternating Current (AC) Measurements 1.2 Representation and Measurement Waveform Representation: DC can be represented as a straight horizontal line on a graph where voltage (or current) is plotted against time. 9 September 2024 Page 7 Module II, Lesson 1: Direct Current (DC) and Alternating Current (AC) Measurements Measurement: DC voltage and current can be measured using voltmeters and ammeters respectively, which are calibrated to read constant values. 9 September 2024 Page 8 Module II, Lesson 1: Direct Current (DC) and Alternating Current (AC) Measurements 2. Introduction to Alternating Current (AC) 2.1 Definition and Characteristics Definition: Alternating Current (AC) is the type of electrical current that periodically reverses direction. The voltage alternates in polarity and magnitude over time. Characteristics: Bidirectional Flow: Current alternates direction periodically, typically in a sinusoidal waveform. Variable Voltage: Voltage varies in magnitude and direction, often described by its peak, peak-to-peak, and RMS (Root Mean Square) values. Examples: Household electrical power, AC generators, and power grids. 9 September 2024 Page 9 Module II, Lesson 1: Direct Current (DC) and Alternating Current (AC) Measurements 2.2 Representation and Measurement Waveform Representation: AC is typically represented by a sinusoidal waveform on a graph where voltage (or current) varies in a sinusoidal pattern over time. 9 September 2024 Page 10 Module II, Lesson 1: Direct Current (DC) and Alternating Current (AC) Measurements Measurement: AC voltage and current are measured using multimeters or oscilloscopes. Multimeters provide RMS values for practical use, while oscilloscopes can display the waveform. 9 September 2024 Page 11 Module II, Lesson 1: Direct Current (DC) and Alternating Current (AC) Measurements 3. Comparison of DC and AC DC Key Differences AC Flows in a single Reverses direction DIRECTION OF FLOW direction periodically Voltage fluctuates in a Voltage is constant VOLTAGE BEHAVIOR sinusoidal or other periodic pattern Less efficient for long- More efficient for long- distance transmission TRANSMISSION distance transmission due to energy losses using transformers 9 September 2024 Page 12 Module II, Lesson 1: Direct Current (DC) and Alternating Current (AC) Measurements 9 September 2024 Page 13 Module II, Lesson 1: Direct Current (DC) and Alternating Current (AC) Measurements For AC, the use of transformers can raise or “step-up” the voltage from low level to high level. From volts to kilovolts, or from kilovolts to Megavolts. The higher the voltage, the stronger the “pushing force”, making the current travel long distances. Therefore, AC is better for transmission of electric power over long distances. 9 September 2024 Page 14 Module II, Lesson 1: Direct Current (DC) and Alternating Current (AC) Measurements 3.2 Advantages and Disadvantages DC Advantages: Stable Voltage: Ideal for sensitive electronic equipment. Simple Circuit Design: Easier to design circuits that require a constant voltage. DC Disadvantages: Transmission Losses: High losses in long-distance transmission. Cost: More expensive to convert DC to different voltage levels. 9 September 2024 Page 15 Module II, Lesson 1: Direct Current (DC) and Alternating Current (AC) Measurements AC Advantages: Efficient Transmission: Lower losses over long distances. Transformers: Easy to transform voltage levels using transformers. AC Disadvantages: Complexity: Requires more complex circuit design for power conditioning. Harmonics: Can produce harmonics and interference in electrical systems. 9 September 2024 Page 16 Module II, Lesson 1: Direct Current (DC) and Alternating Current (AC) Measurements 4. Applications of DC and AC 4.1 Direct Current Applications Electronics: Used in devices requiring a constant voltage. Battery-Powered Devices: Phones, laptops, and portable gadgets. Control Systems: DC motors in robotics and automation. 9 September 2024 Page 17 Module II, Lesson 1: Direct Current (DC) and Alternating Current (AC) Measurements 4.2 Alternating Current Applications Power Distribution: Used in residential and industrial power distribution systems. Household Appliances: AC is used in most household appliances and fixtures. Industrial Equipment: AC motors and equipment in factories and plants. 9 September 2024 Page 18 Module II, Lesson 1: Direct Current (DC) and Alternating Current (AC) Measurements 5. Measurement Tools for DC and AC 5.1 DC Measurement Tools DC Voltmeter: Measures constant DC voltage. Connect in parallel with the component under test. DC Ammeter: Measures constant DC current. Connect in series with the circuit. Multimeter: Can measure both DC voltage and current. 9 September 2024 Page 19 Module II, Lesson 1: Direct Current (DC) and Alternating Current (AC) Measurements 5.2 AC Measurement Tools AC Voltmeter: Measures AC voltage. Usually equipped with RMS measurement capabilities. AC Ammeter: Measures AC current, often including features to measure RMS values. Multimeter: Can also measure both AC voltage and current Oscilloscope: Displays AC waveforms, allowing for detailed analysis of waveform characteristics like frequency, amplitude, and phase. 9 September 2024 Page 20 Module II, Lesson 2: Moving Coil Instruments EMTC 111 – Electrical/Electronic Measuring Instruments 9 September 2024 Page 21 Module II, Lesson 2: Moving Coil Instruments Objective: To understand the construction, working principle, and applications of moving coil instruments, which are widely used for measuring electrical quantities like current and voltage in both analog and digital formats. 9 September 2024 Page 22 Module II, Lesson 2: Moving Coil Instruments Topics Covered: 1. Introduction to Moving Coil Instruments 2. Construction of Moving Coil Instruments 3. Principle of Operation 4. Types of Moving Coil Instruments 5. Applications and Calibration 9 September 2024 Page 23 Module II, Lesson 2: Moving Coil Instruments 1. Introduction to Moving Coil Instruments 1.1 Overview Purpose: Moving coil instruments are used to measure electrical quantities such as voltage and current. They are characterized by their accuracy and sensitivity, making them suitable for precise measurements. Design: These instruments use a moving coil mechanism to provide a visual indication of the measurement on a scale. 9 September 2024 Page 24 Module II, Lesson 2: Moving Coil Instruments 9 September 2024 Page 25 Module II, Lesson 2: Moving Coil Instruments 1.2 Historical Context Development: Moving coil instruments have been in use since the late 19th century and represent a significant advancement in analog measurement technology. They are renowned for their high accuracy and ease of use. 9 September 2024 Page 26 Module II, Lesson 2: Moving Coil Instruments 2. Construction of Moving Coil Instruments 2.1 Key Components Moving Coil Permanent Magnet Iron Core Pointer and Scale Control Mechanism Pivot and Jewel Bearings 9 September 2024 Page 27 Module II, Lesson 2: Moving Coil Instruments Moving Coil: Construction: The moving coil is a coil of wire mounted on a pivot and placed within a magnetic field. Function: It rotates in response to the current flowing through it, moving a needle across a calibrated scale. 9 September 2024 Page 28 Module II, Lesson 2: Moving Coil Instruments Permanent Magnet: Construction: A high- strength permanent magnet creates a stable magnetic field within which the moving coil operates. Function: The magnetic field interacts with the current flowing through the coil, causing the coil to move. 9 September 2024 Page 29 Module II, Lesson 2: Moving Coil Instruments Iron Core: Construction: The iron core is made from a material with high magnetic permeability, meaning it can become magnetized easily and strengthen the magnetic field. Function: The iron core enhances the strength of the magnetic field produced by the stationary permanent magnet. 9 September 2024 Page 30 Module II, Lesson 2: Moving Coil Instruments Pointer and Scale: Construction: A pointer attached to the moving coil indicates the measurement on a calibrated scale. Function: Provides a visual representation of the electrical quantity being measured. 9 September 2024 Page 31 Module II, Lesson 2: Moving Coil Instruments Control Mechanism: Construction: Includes a spring or mechanical stop to return the coil to its initial position when the current is removed. Function: Ensures that the pointer returns to zero or the starting position when not in use. 9 September 2024 Page 32 Module II, Lesson 2: Moving Coil Instruments Pivot and Jewel Bearings: Construction: The coil is mounted on a pivot with jewel bearings to minimize friction and ensure smooth movement. Function: Allows the coil to rotate freely within the magnetic field. 9 September 2024 Page 33 Module II, Lesson 2: Moving Coil Instruments 3. Principle of Operation A moving coil instrument operates on the principle of electromagnetic induction. It consists of a coil of wire suspended in a magnetic field. When an electric current flows through the coil, it generates a magnetic field that interacts with the stationary magnetic field of a permanent magnet. This interaction creates a torque that causes the coil and an attached pointer to rotate. The angle of rotation is proportional to the current passing through the coil, allowing the instrument to measure electrical current or voltage. 9 September 2024 Page 34 Module II, Lesson 2: Moving Coil Instruments 9 September 2024 Page 35 Module II, Lesson 2: Moving Coil Instruments 4. Types of Moving Coil Instruments 4.1 Moving Coil Voltmeters 4.2 Moving Coil Ammeters 4.3 Moving Coil Multimeters 4.4 Moving Coil Galvanometers 9 September 2024 Page 36 Module II, Lesson 2: Moving Coil Instruments 4.1 Moving Coil Voltmeters Design: These instruments measure voltage by using a moving coil mechanism. Range: Typically equipped with a range switch to measure various voltage levels. Application: Used to measure the potential difference across components or circuits. 9 September 2024 Page 37 Module II, Lesson 2: Moving Coil Instruments 4.2 Moving Coil Ammeters Design: Measures current by placing the moving coil in series with the circuit. Range: Often includes shunt resistors to extend the measurement range for higher currents. Application: Used to measure the current flowing through a circuit. 9 September 2024 Page 38 Module II, Lesson 2: Moving Coil Instruments 4.3 Moving Coil Multimeters Design: Combine voltmeter and ammeter functions into a single instrument. Features: Include multiple ranges and functions for measuring voltage, current, and resistance. Application: Versatile tool for general-purpose electrical measurements. 9 September 2024 Page 39 Module II, Lesson 2: Moving Coil Instruments 4.4 Moving Coil Galvanometers Design: Highly sensitive instruments used to detect small currents or voltages. Application: Often used in laboratory settings for precise measurements and experimental setups. 9 September 2024 Page 40 Module II, Lesson 2: Moving Coil Instruments 5. Applications Electrical Measurement: Used in various electrical and electronic applications to measure voltage, current, and resistance. Testing and Troubleshooting: Useful for diagnosing faults and verifying circuit performance. Instrumentation: Employed in scientific instruments and laboratory experiments for accurate measurements. 9 September 2024 Page 41 Module II, Lesson 3: Moving Iron and Electrodynamic Instruments EMTC 111 – Electrical/Electronic Measuring Instruments 9 September 2024 Page 42 Module II, Lesson 3: Moving Iron and Electrodynamic Instruments Objective: To understand the construction, operation, and applications of Moving Iron and Electrodynamic instruments, which are essential for measuring electrical quantities like voltage, current, and power. This lesson covers the principles, types, and practical uses of these instruments. 9 September 2024 Page 43 Module II, Lesson 3: Moving Iron and Electrodynamic Instruments 1. Moving Iron Instruments 1.1 Introduction to Moving Iron Instruments Purpose: Moving iron instruments are used for measuring AC and DC electrical quantities. They are widely used due to their robustness and ease of use. Design: These instruments use the interaction of magnetic fields to drive a moving element (iron vane) which indicates the measurement on a scale. 9 September 2024 Page 44 Module II, Lesson 3: Moving Iron and Electrodynamic Instruments 1.2 Construction of Moving Iron Instruments Iron Vane Stationary Coil Pointer and Scale Damping Mechanism 9 September 2024 Page 45 Module II, Lesson 3: Moving Iron and Electrodynamic Instruments 1.2 Construction of Moving Iron Instruments Iron Vane: Construction: The moving iron vane is a piece of soft iron mounted on a pivot. It is subjected to the magnetic field created by the current flowing through a stationary coil. Function: The vane moves in response to the magnetic field, providing a measurement indication. 9 September 2024 Page 46 Module II, Lesson 3: Moving Iron and Electrodynamic Instruments Stationary Coil: Construction: A stationary coil generates the magnetic field in which the moving iron vane operates. Function: The coil is usually wound around a core and connected to the circuit whose current or voltage is to be measured. 9 September 2024 Page 47 Module II, Lesson 3: Moving Iron and Electrodynamic Instruments Pointer and Scale: Construction: A pointer attached to the moving iron vane moves across a calibrated scale. Function: The pointer provides a visual indication of the measurement. 9 September 2024 Page 48 Module II, Lesson 3: Moving Iron and Electrodynamic Instruments Damping Mechanism: Purpose: To prevent oscillations and ensure steady readings. Types: Air friction or eddy current damping is commonly used. 9 September 2024 Page 49 Module II, Lesson 3: Moving Iron and Electrodynamic Instruments 1.3 Principle of Operation A moving iron instrument operates based on the principle of varying magnetic reluctance. It consists of a coil and a movable iron piece. When an electric current flows through the coil, it creates a magnetic field that magnetizes the iron piece. This magnetization causes a force that moves the iron piece within the coil. The movement of the iron piece is proportional to the current, and this displacement is used to drive a pointer on a scale to indicate the measured value. 9 September 2024 Page 50 Module II, Lesson 3: Moving Iron and Electrodynamic Instruments 1.4 Types of Moving Iron Instruments Attraction Type: Design: The iron vane is attracted to a stationary iron core. Usage: Primarily used in AC measurements. 9 September 2024 Page 51 Module II, Lesson 3: Moving Iron and Electrodynamic Instruments Repulsion Type: Design: The iron vane is repelled by a stationary iron core with the same magnetic polarity. Usage: Used for both AC and DC measurements, providing better linearity and accuracy for DC measurements. 9 September 2024 Page 52 Module II, Lesson 3: Moving Iron and Electrodynamic Instruments 1.5 Applications AC and DC Voltage Measurement: Suitable for a wide range of voltage and current measurements. Power Measurement: Often used in power meters due to their ability to measure the RMS value of AC signals. 9 September 2024 Page 53 Module II, Lesson 3: Moving Iron and Electrodynamic Instruments 2. Electrodynamic Instruments 2.1 Introduction to Electrodynamic Instruments Purpose: Electrodynamic instruments are used for precise measurements of electrical quantities such as current, voltage, and power. They are known for their accuracy and ability to measure both AC and DC signals. Design: These instruments use the interaction of two magnetic fields to produce a deflection that is proportional to the measured quantity. 9 September 2024 Page 54 Module II, Lesson 3: Moving Iron and Electrodynamic Instruments 9 September 2024 Page 55 Module II, Lesson 3: Moving Iron and Electrodynamic Instruments 2.2 Construction of Electrodynamic Instruments Moving Coil System: Construction: The moving coil system consists of a coil that is suspended in the magnetic field of a stationary permanent magnet or electromagnet. Function: The coil moves in response to the interaction of its magnetic field with the stationary magnetic field. 9 September 2024 Page 56 Module II, Lesson 3: Moving Iron and Electrodynamic Instruments Stationary Magnetic Field: Construction: A strong, stable magnetic field is created by stationary permanent magnets or electromagnets. Function: Provides a constant magnetic field in which the moving coil operates. Pointer and Scale: Construction: A pointer attached to the moving coil indicates the measurement on a calibrated scale. Function: Provides a visual representation of the measured value. Damping Mechanism: Purpose: Prevents oscillation and ensures stable readings. Types: Air friction or eddy current damping is used to stabilize the pointer. 9 September 2024 Page 57 Module II, Lesson 3: Moving Iron and Electrodynamic Instruments 2.3 Principle of Operation An electrodynamic instrument operates on the principle of electromagnetic force between two current-carrying coils. It has a fixed coil and a movable coil, both placed in a magnetic field. When an electric current flows through the coils, it creates magnetic forces between them. These forces cause the movable coil to rotate. The rotation is proportional to the current passing through the coils, and this movement drives a pointer or display to indicate the measured value. 9 September 2024 Page 58 Module II, Lesson 3: Moving Iron and Electrodynamic Instruments 2.4 Types of Electrodynamic Instruments Electrodynamic Voltmeters: Design: Measures voltage by deflecting a moving coil in a stationary magnetic field. Usage: Suitable for both AC and DC voltage measurements. Electrodynamic Ammeters: Design: Measures current by detecting the force on a moving coil within a magnetic field. Usage: Used for measuring current in AC and DC circuits. Electrodynamic Wattmeters: Design: Measures power by combining voltage and current measurements through separate coils. Usage: Used for precise power measurements in AC and DC circuits. 9 September 2024 Page 59 Module II, Lesson 3: Moving Iron and Electrodynamic Instruments 2.5 Applications Precision Measurement: Used in laboratory settings and industrial applications where accurate measurements are required. Power Measurement: Commonly used in power meters due to their accuracy and ability to measure both AC and DC power. 9 September 2024 Page 60 Module II, Lesson 4: Ohmmeter, Ammeter, Voltmeter, and Wattmeter EMTC 111 – Electrical/Electronic Measuring Instruments 9 September 2024 Page 61 Module II, Lesson 4: Ohmmeter, Ammeter, Voltmeter, and Wattmeter Objective: To gain a theoretical understanding of how ohmmeters, ammeters, voltmeters, and wattmeters measure electrical properties. 9 September 2024 Page 62 Module II, Lesson 4: Ohmmeter, Ammeter, Voltmeter, and Wattmeter 1. Ohmmeter 1.1 Purpose and Function Purpose: An ohmmeter is used to measure electrical resistance in ohms (Ω). It determines how much resistance is present in a component or circuit. Function: It applies a small voltage across a resistor or circuit and measures the current flowing through it. 9 September 2024 Page 63 Module II, Lesson 4: Ohmmeter, Ammeter, Voltmeter, and Wattmeter Ohmmeters can be either connected in series or parallel based on requirements (whether resistance being measured is part of circuit or is a shunt resistance). 9 September 2024 Page 64 Module II, Lesson 4: Ohmmeter, Ammeter, Voltmeter, and Wattmeter 1.2 Types of Ohmmeters Analog Ohmmeter: Design: Features a moving-coil meter with a pointer and a calibrated scale. Operation: Measures resistance by balancing a current with a known reference resistor. Use: Suitable for measuring a wide range of resistances, but less precise compared to digital ohmmeters. 9 September 2024 Page 65 Module II, Lesson 4: Ohmmeter, Ammeter, Voltmeter, and Wattmeter Digital Ohmmeter: Design: Provides a digital readout of resistance values. Operation: Uses electronic components and microprocessors to measure resistance. Advantages: Offers higher precision, easier to read, and often includes additional features like range selection and automatic zero adjustment. 9 September 2024 Page 66 Module II, Lesson 4: Ohmmeter, Ammeter, Voltmeter, and Wattmeter 1.3 Usage and Calibration Usage: Measurement: Ensure the component or circuit is de-energized before measuring. Connect the ohmmeter leads to the component terminals or circuit points. Range Selection: Set the meter to the appropriate resistance range. Start with a higher range and move to lower ranges if needed. Calibration: Zero Adjustment: Before measuring, ensure the ohmmeter reads zero when the leads are shorted together. Reference Checks: Periodically check against known resistors to ensure accuracy. 9 September 2024 Page 67 Module II, Lesson 4: Ohmmeter, Ammeter, Voltmeter, and Wattmeter 1.4 Applications Component Testing: Verify the resistance of resistors, cables, and other components. Circuit Diagnostics: Identify faulty components or connections with excessive resistance. 9 September 2024 Page 68 Module II, Lesson 4: Ohmmeter, Ammeter, Voltmeter, and Wattmeter 2. Ammeter 2.1 Purpose and Function Purpose: An ammeter measures the electrical current flowing through a circuit, expressed in amperes (A). Function: It measures the amount of charge passing through a conductor over time. It is typically connected in series with the circuit. 9 September 2024 Page 69 Module II, Lesson 4: Ohmmeter, Ammeter, Voltmeter, and Wattmeter Ammeters are connected in series with the circuit. A series connection is used because objects in series have the same current passing through them. 9 September 2024 Page 70 Module II, Lesson 4: Ohmmeter, Ammeter, Voltmeter, and Wattmeter 2.2 Types of Ammeters Analog Ammeter: Design: Consists of a moving-coil meter with a pointer that moves across a calibrated scale. Operation: Measures current by detecting the magnetic field created by the current flowing through the coil. Use: Suitable for general-purpose measurements and visual indications of current levels. 9 September 2024 Page 71 Module II, Lesson 4: Ohmmeter, Ammeter, Voltmeter, and Wattmeter Digital Ammeter: Design: Provides a digital display of current measurements. Operation: Uses electronic circuitry to measure and display current accurately. Advantages: Higher accuracy, ability to measure very small currents, and additional features such as auto-ranging. 9 September 2024 Page 72 Module II, Lesson 4: Ohmmeter, Ammeter, Voltmeter, and Wattmeter 2.3 Usage and Calibration Usage: Measurement: Connect the ammeter in series with the circuit to measure current. Ensure the circuit is de-energized while connecting the ammeter. Range Selection: Select the appropriate current range based on the expected current level. Calibration: Zero Adjustment: Some ammeters require zero adjustment when no current is flowing. Reference Checks: Verify accuracy using known current sources or calibration standards. 9 September 2024 Page 73 Module II, Lesson 4: Ohmmeter, Ammeter, Voltmeter, and Wattmeter 2.4 Applications Current Measurement: Monitor and measure current in various electrical and electronic circuits. Troubleshooting: Identify current issues or verify proper operation of circuit components. 9 September 2024 Page 74 Module II, Lesson 4: Ohmmeter, Ammeter, Voltmeter, and Wattmeter 3. Voltmeter 3.1 Purpose and Function Purpose: A voltmeter measures the electrical potential difference (voltage) between two points in a circuit, expressed in volts (V). Function: It measures the potential difference without significantly affecting the circuit. Typically connected in parallel with the points of interest. 9 September 2024 Page 75 Module II, Lesson 4: Ohmmeter, Ammeter, Voltmeter, and Wattmeter The voltmeter is connected in parallel with the circuit. The voltmeter is connected to the two points in the circuit where you want to measure the voltage drop. 9 September 2024 Page 76 Module II, Lesson 4: Ohmmeter, Ammeter, Voltmeter, and Wattmeter 3.2 Types of Voltmeters Analog Voltmeter: Design: Features a moving-coil meter with a needle and a calibrated scale. Operation: Measures voltage by detecting the magnetic field produced by the current flowing through a coil. Use: Useful for measuring voltage levels in various circuits and systems. Digital Voltmeter: Design: Provides a digital readout of voltage measurements. Operation: Uses electronic circuits to measure and display voltage accurately. Advantages: Higher precision, easier to read, and often includes features such as auto-ranging and higher resolution. 9 September 2024 Page 77 Module II, Lesson 4: Ohmmeter, Ammeter, Voltmeter, and Wattmeter 3.3 Usage and Calibration Usage: Measurement: Connect the voltmeter in parallel with the component or circuit points where the voltage is to be measured. Range Selection: Set the meter to an appropriate voltage range to avoid overloading. Calibration: Zero Adjustment: Some digital voltmeters may require zero adjustment or calibration using known voltage sources. Reference Checks: Regularly compare against calibrated voltage sources to ensure accuracy. 9 September 2024 Page 78 Module II, Lesson 4: Ohmmeter, Ammeter, Voltmeter, and Wattmeter 3.4 Applications Voltage Measurement: Measure the voltage across components, power supplies, and circuits. Diagnostic Testing: Check voltage drops, verify power supply outputs, and troubleshoot electrical issues. 9 September 2024 Page 79 Module II, Lesson 4: Ohmmeter, Ammeter, Voltmeter, and Wattmeter 4. Wattmeter 4.1 Purpose and Function Purpose: A wattmeter measures the electrical power in a circuit, expressed in watts (W). It determines how much power is consumed or delivered by a component or system. Function: It calculates power by measuring both voltage and current, and multiplying them to get the power. It can also account for the phase angle in AC circuits. 9 September 2024 Page 80 Module II, Lesson 4: Ohmmeter, Ammeter, Voltmeter, and Wattmeter A wattmeter consists of two main components: the current coil (CC) and the potential coil (PC). The CC is connected in series with the load, carrying the load current (I), while the PC is connected in parallel to the load, across which the load voltage (V) is applied. 9 September 2024 Page 81 Module II, Lesson 4: Ohmmeter, Ammeter, Voltmeter, and Wattmeter 4.2 Types of Wattmeters Analog Wattmeter: Design: Typically consists of two coils (voltage coil and current coil) and a pointer to indicate power on a calibrated scale. Operation: Measures power by using the interaction between the magnetic fields of the two coils. Use: Suitable for general-purpose power measurements and visual indication. 9 September 2024 Page 82 Module II, Lesson 4: Ohmmeter, Ammeter, Voltmeter, and Wattmeter Digital Wattmeter: Design: Provides digital readings of power measurements. Operation: Uses electronic components to measure voltage and current, and calculate power with higher precision. Advantages: Accurate measurements, ability to display power factor, and often includes additional features like power consumption over time. 9 September 2024 Page 83 Module II, Lesson 4: Ohmmeter, Ammeter, Voltmeter, and Wattmeter 4.3 Usage and Calibration Usage: Measurement: Connect the wattmeter in parallel and series with the circuit, depending on whether measuring AC or DC power. Range Selection: Select the appropriate power range based on the expected power level. Calibration: Reference Checks: Use known power sources to ensure accurate measurements and adjust if necessary. 9 September 2024 Page 84 Module II, Lesson 4: Ohmmeter, Ammeter, Voltmeter, and Wattmeter 4.4 Applications Power Measurement: Measure the power consumed by electrical devices and systems. Efficiency Testing: Evaluate the efficiency of electrical appliances and circuits by measuring input and output power. 9 September 2024 Page 85