How to choose proper parameters for Chebyshev digital filtering function?

[Paul_k1]

Hello,

We have to use a filter function in our program written in VB.NET in order to filter data. Currently, the function is as follows:

data = frmMain.AxCWDSP.ChLPF(testData, sampleFreq, 15, 8, 1)

In our application, we collect data from the sensors while the object is spinning at different RPM speeds (from 300 to 3000 RPM). 

My problem is that I need to understand whether my filtering of the collected data is working properly or not since I'm not quite understanding this function. So far, I know that:

"ChLPF(testData, sampleFreq, 15, 8, 1)"

stands for :

Chebyshev low-pass filtering with the parameters:

"ImpResponse, sample frequency, low cut off frequency, Ripple, Order"

My questions are:

How do I choose sample frequence? Is it related to RPM speed in Hz or is it data sample count?

How do I choose Ripple? the values that I get from the sensor vary from about +- 0.001, so my ripple should be very small then?

How do I choose Order? I was reading that "order referes to number of Poles, and the more poles, the better". Is it true? If so, what exact number shoud it be?

How do I choose proper low-cut frequency? based on my lowest RPM that I use such as 300RPM / 60 = 5Hz?

On this website, I was able to find the IRF Filter program which allows me to select different filters and play with different settings. However, I'm not sure what do Amplitude and phase graphs represent? Should these graphs look as similar as possible like on the picture that I attached?

Please let me know If I have to provide more information.

Thanks,

Paul.

[PedroMunoz]

Hi Paul:

The frequency in Chebyshev filter is the frequency at which you want to sample the input signal and it must be greater than 0. The ripple is the maximum permisible passband loss in decibels and it must be greater than 0. The low cutoff frequency most observe the Nyquist criterion, so that means that it mst be half of the sampling frequency.

[Paul_k1]

Thank you so much for the reply.

Most of it making sense to me except for the units of frequency. Is it supposed to be in Herts (about 55 hz) or in frequency sample rate (about 2000 samples)?

Paul.