Digital energy meter operates on the principle of

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Examoogle · Accepted Answer

Digital Integration

Explanation: A digital energy meter operates by continuously measuring instantaneous power and integrating it over time to calculate total energy consumption. The integration process is realized digitally using microcontrollers or dedicated DSP chips that sample voltage and current inputs at high frequencies.

Working Principle: The instantaneous power $p(t) = v(t) 	imes i(t)$ is calculated by the digital signal processor. The energy consumed $E$ is the integral of this power over time, expressed as $E = \int v(t)i(t) dt$. In a digital system, this is computed as a discrete sum $\sum p(n) 	imes \Delta t$, effectively performing numerical integration to update the register value.

Key Formulas: $E = \int_{0}^{T} v(t) i(t) dt$ — Continuous time energy calculation; $E \approx \sum_{n=1}^{N} v(n) i(n) \Delta t$ — Digital (Discrete) integration method

Key Points: Digital energy meters eliminate moving parts present in Ferraris-type induction meters.; They utilize Analog-to-Digital Converters (ADC) to sample voltage and current signals.; Multiplication and summation are performed in the digital domain to derive active power.; High accuracy, immunity to mechanical vibrations, and tampering detection are key features.

Advantages: High accuracy over a wide range of current; Low power consumption of the meter itself; Capability for remote monitoring and multi-tariff recording

Disadvantages: Susceptibility to electromagnetic interference (EMI); More complex circuitry compared to electro-mechanical meters

Applications: Smart grid metering; Residential and industrial power consumption billing; Real-time power quality monitoring

Additional Info: Digital meters sample signals at rates determined by the Nyquist-Shannon sampling theorem to prevent aliasing.. Option B and C are incorrect as addition/subtraction are merely elementary arithmetic operations, whereas energy is the accumulation (integration) of power over a time interval.

Answer: A is correct — Digital energy meters function by sampling voltage and current waveforms and performing discrete digital integration to calculate cumulative energy.

Exam Tip: Always remember that 'energy' is time-integral of 'power', and in a digital environment, this integration is implemented as a cumulative summation of sampled products.

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