Peak to Peak

Peak to Peak (pk-pk) is the difference between the maximum positive and the maximum negative amplitudes of a wave form, as shown below. If there is no direct current (DC) component in an alternating current (AC) wave, then the pk-pk amplitude is twice the amplitude.

 

 

For an AC sine wave with no DC component, the pk-pk amplitude is equal to approximately 2.828 times the root-mean-square (RMS) amplitude. pk-pk values can be expressed for voltage (the usual case), current, or power.

Peak-to-peak amplitude is the change between peaks (highest amplitude value) and trough (lowest amplitude value, which can be negative). With appropriate circuitry, pk-pk amplitudes of electric oscillations can be measured by meters or by viewing the waveform on an oscilloscope. Pk-pk is a straightforward measurement on an oscilloscope, the peaks of the waveform being easily identified and measured against the graticule. This remains a common way of specifying amplitude, but sometimes other measures of amplitude are more appropriate.

The pk-pk value is used, for example, when choosing rectifiers for power supplies, or when estimating the maximum voltage that insulation must withstand. Some common voltmeters are calibrated for RMS amplitude, but respond to the average value of a rectified waveform. Many digital voltmeters and all moving coil meters are in this category. The RMS calibration is only correct for a sine wave input since the ratio between peaks, average and RMS values is dependent on waveform. If the wave shape being measured is greatly different from a sine wave, the relationship between RMS and average value changes. True RMS-responding meters were used in radio frequency measurements, where instruments measured the heating effect in a resistor to measure a current. The advent of microprocessor-controlled meters capable of calculating RMS by sampling the waveform has made true RMS measurement commonplace.