The amount of ripples in a dc source is indicated by the ripple factor which is defined as the ratio of the rms value of the ripple voltage to the absolute value of the dc voltage.
Ripple factor(γ)= (Vripple(rms)/Vdc)*100
Thus if we have 10V dc supply with a variation between 9.5 to 10.5 volts, the ripple factor would be (.5/5)*100 which indicates a ripple factor of 5%.
The peak-to-peak value of the ripples at the output of a full wave rectifier is given by
In the case of a half wave rectifier, the peak voltage is given by
where I is the current in the circuit, f is the frequency and C is the value of capacitance that is connected in parallel to filter the ripples
Ripples can be measured in the field by an ordinary multimeter. Set the multimeter to measure AC voltage, and check the voltage at the output of the power supply. Any ripples would reflect as an AC voltage. Now, set the multimeter to dc voltage and measure the actual dc output. The Ripple factor is the ratio of the ac voltage to the dc voltage.
Effects of Ripples
Ripples can cause failure of components such as capacitors and can cause heating and failure in certain electronic components.
In audio circuits, the ripples can be reflected as noise, as the frequency of the ripples is within the audio band.
Ripples can also interfere in TV displays