Question: In a CapSense application, why does noise decrease when resolution is increased?
Response: Noise decreases when resolution increases due to the nature of the oversampling incremental measurement method. The higher the resolution is, the longer the period is that you are measuring the sensor. The longer the period is, the more noise gets filtered out. Please refer to the user module datasheet of the ADCINC User Module in the PSoC Designer software. Figure showing the frequency response and affect of oversampling is shown below:
The graph is normalized to the sample rate (or scan rate) of the system. Observe that noise in the system will get filtered out. The higher the noise frequency is, the more it gets attenuated. Noise with a frequency that is a multiple of the sample rate gets completely filtered out.
So, if the resolution is increased, the sample rate will decrease, and the sample period will increase. If the sample rate decreases, it means that a lot more system noise will be filtered out.