Electrical signal power and energy calculations by example

In electronics and signal processing, you have to deal with electrical signals. In many cases, you may need to calculate signal powerand energy. Power and energy for DC In a standard situation, when DC power supply is applied to a known resistor or another device like an LED, motor you can calculate its power very easy by applying Ohms law: If we rung this device for time T then we can calculate total energy used: In some cases, you may not know the resistance of your circuit. In this case, you can measure the current flow. So your power formula can be transformed by using same Ohms law:

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Signal power and energy calculation

The most common signal characteristics are energy and power. In signal theory, these terms require additional comments because they are a bit different from these what we are using in AC or DC systems. What are power and energy? When we connect R resistor to voltage U, then the resistor will dissipate some power which is equal P=U2/R. During time T the energy loss on this resistor will be E= TU2/R. Now let us say that we add some signal s() instead of DC voltage. In this case, the power will depend on time as the signal is time dependent. The term is called instantaneous power: p(s)=s(t)2/R to calculate energy loss during time T we need to integrate: Sometimes it is more convenient to evaluate average power during some time T: When we talk about signal power, we don’t care about R load. Therm Signal power usually is used for comparing different signals. For this it is agreed to use R=1, then we exclude resistance from the formulation, and then we can talk about signal power and energy in signal theory: p(t) = s^{2}(t) Signal energy may be finite and infinite. For instance, a finite signal will have limited length…

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