Digital voltmeter converts ________.
Analog to digital signal
Understanding Digital Voltmeters and Signal Conversion
A voltmeter is an instrument used for measuring the potential difference, or voltage, between two points in an electric circuit. Voltmeters come in various forms, including analog and digital.
An analog voltmeter typically uses a needle that moves across a calibrated scale to indicate the voltage value. It directly measures the continuous analog voltage.
A digital voltmeter (DVM), on the other hand, displays the voltage reading as a numerical value, usually on an LCD or LED screen. To display a continuous analog voltage as a discrete numerical value, the digital voltmeter performs a crucial conversion process.
The Core Function: Analog to Digital Conversion
The fundamental operation that distinguishes a digital voltmeter is its ability to convert an analog signal into a digital signal. Here's why this is necessary:
- Electric signals in circuits, like voltage, are often continuous and vary smoothly over time. This is an analog signal.
- Digital displays and processing systems work with discrete values represented by binary digits (bits). This is a digital signal.
- A digital voltmeter takes the analog voltage input and uses an internal circuit, known as an Analog-to-Digital Converter (ADC), to transform this continuous signal into a series of digital codes.
- These digital codes represent the measured voltage value, which is then processed and displayed as a number.
Therefore, the primary function of a digital voltmeter is the conversion from analog voltage to a digital representation.
Evaluating Other Options
Let's look at the other options to understand why they do not describe the main function of a digital voltmeter:
- Resistance to voltage: While voltage, current, and resistance are related by Ohm's Law (\(V = I \times R\)), a voltmeter's primary job is to measure voltage that is already present, not to convert resistance into a voltage. Instruments like ohmmeters measure resistance.
- Current to voltage: Some measurement circuits might convert current to voltage using a known resistance (e.g., a shunt resistor) so that a voltmeter can measure it, but this conversion happens *before* the voltage reaches the voltmeter's core analog-to-digital conversion stage, or is a technique used by instruments like ammeters that work on voltage measurement principles after converting current. The digital voltmeter itself converts the *voltage* it receives.
- Digital to analog signal: This process, performed by a Digital-to-Analog Converter (DAC), is the opposite of what is needed for a digital display. DACs are used in devices like audio players or signal generators to convert digital data back into a continuous analog signal. A digital voltmeter converts analog input to digital output for display.
Conclusion on Digital Voltmeter Conversion
Based on the function of displaying an analog voltage as a numerical value, the digital voltmeter's essential operation is converting the analog input signal into a digital signal that can be processed and shown on a digital display.
| Feature | Analog Voltmeter | Digital Voltmeter |
|---|---|---|
| Output Display | Needle on scale | Numerical display (LCD/LED) |
| Signal Processing | Direct measurement of analog voltage | Converts analog voltage to digital signal (using ADC) |
| Reading Type | Continuous (inferred from needle position) | Discrete numerical value |
| Key Internal Process | Mechanism responding to voltage (e.g., d'Arsonval movement) | Analog-to-Digital Conversion (ADC) |
Revision Table: Key Concepts for Voltmeters
| Term | Definition | Relevance to Voltmeter |
|---|---|---|
| Voltage | Potential difference between two points in a circuit, measured in Volts (V). | What a voltmeter measures. |
| Analog Signal | Continuous signal varying smoothly over time or space. | The type of electrical signal often measured by a voltmeter. |
| Digital Signal | Discrete signal represented by binary values (0s and 1s). | The type of signal processed and displayed by a digital voltmeter. |
| Analog-to-Digital Converter (ADC) | Electronic circuit that converts an analog signal into a digital signal. | The essential component inside a digital voltmeter. |
Additional Information: Types of ADCs used in DVMs
Digital voltmeters utilize different types of Analog-to-Digital Converters (ADCs) to perform the conversion. Some common types include:
- Successive Approximation ADC: A widely used type offering a good balance of speed and resolution.
- Dual-Slope ADC: Often used in high-precision DVMs due to its accuracy and noise immunity, although it is slower.
- Flash ADC: Very fast but can be complex and power-hungry, often used where speed is critical.
The choice of ADC affects the digital voltmeter's speed, accuracy, resolution, and cost.
Important Questions from Miscellaneous
A stone is thrown horizontally from the top of a 20 m high building with a speed of 12 m/s. It hits the ground at a distance R from the building. Taking g = 10 m/s2 and neglecting air resistance will give :
A sphere of volume V is made of a material with lower density than water. While on Earth, it floats on water with its volume f1V (f1 < 1) submerged. On the other hand, on a spaceship accelerating with acceleration a < g (g is the acceleration due to gravity on Earth) in outer space, its submerged volume in water is f2V. Then:
A railway wagon (open at the top) of mass M1 is moving with speed v1 along a straight track. As a result of rain, after some time it gets partially filled with water so that the mass of the wagon becomes M2 and speed becomes v2. Taking the rain to be falling vertically and the water stationery inside the wagon, the relation between the two speeds v1 and v2 is :
Consider the following statements:
1. Distance between the longitudes becomes zero on North Pole and South Pole.
2. Distance between the longitudes is maximum on the Equator.
3. Number of longitudes is more than number of latitudes.
Which of the statements given above is/are correct?
One block of 2⋅0 kg mass is placed on top of another block of 3⋅0 kg mass. The coefficient of static friction between the two blocks is 0⋅2. The bottom block is pulled with a horizontal force F such that both the blocks move together without slipping. Taking acceleration due to gravity as 10 m/s2, the maximum value of the frictional force is :
