![]() ![]() ![]() This difference is called the Form Factor of the wave, and the relationship of 1.11 is only true for a perfect sine wave. If V AV (0.637) is multiplied by 1.11 the answer is 0.707, which is the RMS value. V RMS = V PK x 0.707 and I RMS = I PK x 0.707Īlso, the peak value of a sine wave is equal to 1.414 x the RMS value. It can be shown that the RMS value of a sine wave is 0.707 of the peak value. That is, if an AC sine wave has a RMS value of 240 volts, it will provide the same energy to a circuit as a DC supply of 240 volts. The RMS or ROOT MEAN SQUARED value is the value of the equivalent direct (non varying) voltage or current which would provide the same energy to a circuit as the sine wave measured. There are however some meters that will read the RMS value, these are called "True RMS meters". ![]() The average value is the value that usually determines the voltage or current indicated on a test meter. Using only half a cycle, as illustrated in fig 1.2.3 the average value (voltage or current) is always 0.637 of the peak value of the wave. If the average of the full cycle was taken it would of course be zero, as in a sine wave symmetrical about zero, there are equal excursions above and below the zero line. This is normally taken to mean the average value of only half a cycle of the wave. If the sine wave being measured is symmetrical either side of zero volts (or zero amperes), meaning that the dc level or dc component of the wave is zero volts, then the peak value must be the same as the amplitude, that is half of the peak to peak value.įig 1.2.3 The Average Value of a Sine Wave Average Value In a voltage waveform the peak value may be labelled V PK or V MAX (I PK or I MAX in a current waveform). The reference value normally used is zero. The PEAK value of the wave is the highest value the wave reaches above a reference value. As a sine wave is symmetrical about its centre line, the amplitude of the wave is half the peak to peak value, as shown in Fig 1.2.2. The AMPLITUDE of a sine wave is the maximum vertical distance reached, in either direction from the centre line of the wave. The instantaneous value of a sine wave one quarter of the way through the cycle will be equal to the peak value. often chosen to coincide with some other event. This is the value (voltage or current) of a wave at any particular instant. In a current waveform it would be labelled I PP or I PK−PK as I (not C) is used to represent current. It will be measured in volts on a voltage waveform, and may be labelled V PP or V PK−PK. The PEAK TO PEAK value is the vertical distance between the top and bottom of the wave. ![]()
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