Vega Customer Applications Manual
Section 4 - Output Ripple and Noise
Rev. A3: October 2003
Page 18 of 48
Section 4 - Output Ripple and Noise
The Measurement of ripple and noise.
Lambda measures ripple and noise on switching power supplies using an oscilloscope with the bandwidth limited to
20Mhz. The measurement is taken at the end of a 150mm length pair of twisted cables terminated with 10uF
electrolytic capacitor and 0.1uF ceramic capacitor. The earth wire of the oscilloscope probe should be as short as
possible, winding link wire around the earth collar of the probe is the preffered method.
Noise from a switching power supply is made up of two distinct elements "ripple" and "high frequency". "Ripple" noise
is the variation at the switching frequency of the supply. "High frequency" noise is superimposed on top of the "ripple"
and results in a typical waveform as below.
The term PARD means "Periodic and Random Deviation" and is a measure of the TOTAL noise (ie high fequency
noise + ripple) quoted as peak to peak. This is the figure quoted in the specifications of each module.
Содержание V4FFS 12V12A
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