Why do you get voltage increase on oscilloscope when hand goes near probe. Is this capacitance or RF related?
I am designing a new type of handheld probe. So started design research.
Why do you get a voltage increase on oscilloscope when your hand goes near probe. Is this capacitance related or RF related effect ? If you ground the probe to the body effect disappears ?
Set oscilloscope to 20milliseconds at 50millivolt divisions and you clearly see 50hz waveform from UK 240v mains wall sockets and lab equipment in surrounding area etc...
If you now put your hand near the oscilloscope probe the waveform increases in height.
I am having trouble deciding is this capacitive or RF Related ?
Accepted answer
Its both Capacitive and RF as an EMC function. The probe is an input to a very sensitive amplifier that is biased at a very low voltage level. As you move your hand in front, your hand add parasitic capacitance which is being charged (like a charge pump) to increase the voltage. The closer you move your hand, the higher the increase in capacitance. This parasitic capacitance is common mode capacitance and is known as 'pickup'.
