DESIGN AND CONSTRUCTION OF A DIGITAL MULTIMETER
Abstract
This work is on the design and construction of digital multi-meter using PIC microcontroller. A multimeter is a tool basically used to measure current, voltage and resistance.. In this system, a typical multi-meter may include features such as the ability to measure AC/DC voltage, DC current, resistance, temperature, diodes, frequency and connectivity. This design uses of the PIC microcontroller, voltage rectifiers, voltage divide, potentiometer, LCD and other instruments to complete the measure. When we used what we have learned of microprocessors and adjust the program to calculate and show the measures in the LCD, keypad selected the modes. The software programming has been incorporated using MPLAB and PROTEUS. In this system, the analogue input is taken directly to the analogue input pin of the microcontroller without any other processing. So the input range is from 0V to 5V the maximum source impedance is 2k5 (for testing use a 1k pot). To improve the circuit adds an op-amp in front to present greater impedance to the circuit under test. The output impedance of the op-amp will be low which a requirement of the PIC analogue input is.
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