4. When measuring the input / output voltage ripple, care must be taken to avoid a long ground
return for the oscilloscope probe. After removing the grabber and outer plastic sleeve from the
scope probe, measure the input voltage ripple by touching the probe between V
IN
and GND
and measure the output voltage ripple by touching the probe between V
OUT
and GND as
shown in Figure 2.
VIN
GND
VOUT
GND
MEASURING
V
IN
RIPPLE
MEASURING
V
OUT
RIPPLE
TEKTRONIX
TDS 640A
OSCILLOSCOPE
PROBE
Figure 2. Proper Noise Measurement Technique