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 power and energy. –it is easy with DC In standard situation when DC power supply is applied to known resistor or other device like 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:

Signal power and energy calculation

One of frequently used signal characteristics are energy and power. In signal theory these therms require additional comments because they are a bit different from these what we are used to use in AC or DC systems. What is power and energy? If wee connect R resistor to voltage U, then 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 lets say that we ad some signal s() instead of DC voltage. In this case the power will depend on time as signal is time dependent. The therm is called instantaneous power: p(s)=s(t)2/R in order to calculate energy loss during time T we need to integrate: Sometimes its is more convenient to calculate 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…