I'm measuring the flow of a hall effect flow meter using an MCU and counting pulses. The value calculated by the microcontroller program did not agree with the calibration standard. The MCU value always read higher implying that it was counting more pulses. However, when I connected my scope to measure the frequency I got a value which aligned to the cal standard. And the MCU program also then recorded the correct number of pulses. After some help in another thread it was determined that the capacitance of the probe was making the circuit work by filtering noise. Some experimentation determined that about 100pF eliminated the noise in the circuit and didn't attenuate the frequencies of interest which are <800Hz
While the current problem is solved I want to get a probe that might be better in future similar situations. At 10X my current probe has about 18pF capacitance. I'm considering purchasing a 100X probe. I see some have about 6pF capacitance whereas the more expensive 1000X probes can have about 2-3pF capacitance. Considering my use case will these probes give me a better insight into noise in my circuits. In particular is it realistic to be able to think that the spurious pulses can actually be seen on the scope? Thanks.
While the current problem is solved I want to get a probe that might be better in future similar situations. At 10X my current probe has about 18pF capacitance. I'm considering purchasing a 100X probe. I see some have about 6pF capacitance whereas the more expensive 1000X probes can have about 2-3pF capacitance. Considering my use case will these probes give me a better insight into noise in my circuits. In particular is it realistic to be able to think that the spurious pulses can actually be seen on the scope? Thanks.