Analog Multimeter Project

Project Overview

This project was developed under the EE-365 Industrial Instrumentation and Measurements course at Habib University during Spring 2020. The objective was to design and build an analog multimeter using a d'Arsonval Galvanometer, integrating three key measurement modes: voltmeter, ammeter, and ohmmeter. The project explores the challenges of analog instrumentation, including calibration, component selection, and design integration.

REPORT: https://github.com/SarwanShah/HU_2020_Analog-Multimeter-Design/blob/main/Final_Report.pdf

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Project Features

• Voltmeter: Measures voltages in the range of 0 to 50V.
• Ammeter: Measures currents in the range of 0 to 100mA.
• Ohmmeter: Measures resistances from 1 to 100Ω, with provisions for 10% battery variation.
• Integrated Design: Combines all three instruments into one device with selectable modes.
• Simulation & Hardware Validation: Includes circuit simulations and hardware implementation using veroboard.

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Project Implementation

➤ Galvanometer Calibration

• Internal Resistance (Rm): Measured as 218.4Ω.
• Full-Scale Deflection Current (IFSD): Determined to be 4.195mA through gradual voltage application.

➤ Ammeter Design

• Shunt-Type Design: Utilizes a parallel shunt resistor to limit the current through the galvanometer.
• Shunt Resistance (Rsh): Calculated to be 9.56Ω with a practical combination of 10Ω || 220Ω.

➤ Voltmeter Design

• Series-Type Design: Employs a series resistor to divide the input voltage.
• Multiplier Resistance (Rse): Designed at 11.7kΩ, with a practical combination of 680kΩ || 12kΩ.

➤ Ohmmeter Design

• Series-Type Design: Uses a 9V battery, a fixed resistor for current limiting, and a variable resistor for zero-control.
• Resistor Network: Includes 1734Ω, 192.7Ω, and 2.2kΩ || 8.2kΩ resistors to handle various ranges.

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Simulation Results

➤ Ammeter Simulation

• Linear relationship observed between input current (0–100mA) and galvanometer deflection current (up to 4.195mA).

➤ Voltmeter Simulation

• Linear increase in galvanometer deflection current as input voltage varies from 0 to 50V.

➤ Ohmmeter Simulation

• Inverse proportional relationship between input resistance (1–100kΩ) and galvanometer deflection current.

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Hardware Implementation

• The circuit was implemented on a veroboard, requiring extensive soldering and optimization to minimize interference.
• A manual jumper setup was used to switch between modes instead of slide switches, reducing the risk of simultaneous mode activation.
• Additional resistors