In this note, we are going to know about DMM or Digital Multimeter Block Diagram. Also definition, working, advantages, and applications. Welcome to Poly Notes Hub, a leading destination for engineering notes.
Author Name: Arun Paul.
What is Digital Multimeter or DMM?
A Digital Multimeter (DMM) is an electronic instrument that measures voltage (AC/DC), current, and resistance. It replaces traditional analog meters by providing accurate readings through a digital display. DMMs are commonly used in the electrical and electronic sectors to troubleshoot, test, and repair circuits.
Specification of Digital Multimeter or DMM
- Measures AC and DC voltage up to a specified range (e.g., 200mV to 1000V).
- Offers high accuracy compared to analog meters.
- Digital display with 3½ or 4½ digits for precise readings.
- Some DMMs feature auto-ranging, which selects the appropriate range automatically.
- High input impedance (10MΩ or more) prevents circuit loading.
- Some advanced DMMs include frequency measurement, capacitance measurement, and data logging.
Explain Digital Multimeter Block Diagram
Here is the DMM or Digital Multimeter Block Diagram –
- Input Section: The input terminals are used to attach test leads that measure voltage, current, and resistance. The input part comprises a shunt for measuring current and a switch for selecting AC, DC, or resistance measurements.
- AC Attenuator: When measuring AC voltage, the AC Attenuator lowers the high AC voltage to a level that is suitable for processing. This assures that the circuit components can safely withstand the voltage.
- AC Converter: Before proceeding with any further processing, the AC Converter converts the AC voltage signal into a DC signal. This is important because digital circuitry employ DC signals.
- DC Attenuator: The DC Attenuator decreases large DC voltages to lower levels, ensuring precise and safe measurements.
- Ohms Converter: When measuring resistance, the circuit sends the input signal to the Ohms converter. This block applies a known voltage and monitors the resulting current to determine resistance using Ohm’s Law.
- Analog to Digital Converter: The A/D converter is a critical component that converts the processed analog signal to a digital signal. The digital data is then displayed and processed.
- Precision Reference: The Precision Reference offers a constant reference voltage, ensuring accurate analog-to-digital conversion. This increases the reliability and precision of the readings.
- Digital Display: The final measurement result is shown numerically on the digital display (often an LCD screen or LED screen).
- BCD Output & Interface: The BCD (Binary-Coded Decimal) Output and Interface connect the multimeter to external devices such as computers or printers for data logging and analysis.
Digital Multimeter Working Principle
The operation of a Digital Multimeter (DMM) consists of numerous steps. First, the user picks a measuring mode, such as voltage, current, or resistance. The input signal is then routed through the proper attenuator, whether AC/DC or an Ohms Converter. If AC voltage is measured, the signal is first converted to DC using the AC Converter.
The processed signal is then transferred to the A/D Converter, where it is digitized to ensure precise measurement. A precision reference ensures that the conversion is precise. Finally, the Digital Display displays the digital output numerically. If necessary, the BCD Output and Interface can send the data to other devices for further processing.
Advantages of Digital Multimeter
Here we have listed some digital multimeter advantages –
- This type of meter provides precise readings compared to analog meters.
- The Digital display on this meter eliminates human errors in reading scale values.
- The digital multimeter is compact and portable.
- This meter operated on battery. It has low power consumption.
- It can measure voltage, current, resistance, and more in a single device.
Digital Multimeter Applications
Here we have listed some applications of digital multimeter –
- Used by technicians for testing circuits, troubleshooting faults, and repairing devices.
- Essential for checking voltage, current, and resistance in wiring and electrical systems.
- Helps in testing car batteries, sensors, and electronic components.
- Used in power plants, manufacturing units, and automation industries for maintenance.
- Used by students and professionals for learning electrical and electronic concepts.
- Important in labs for prototyping and testing electronic components.