Peak to peak time, or frequency calculation

T

Tim

Hi

I have imported the trace of a waveform into Excel (x=time, y=volts).
I can manually measure the time between peaks and the frequency, but I
want to know if there is a formular or equation that can do that
automatically for parts of or the whole data series.

It has a frequency range from 10 to 50 hz and I want to know the
frequency of several 60second recordings.

Any help much appreciated.

Tim
 
B

Bernie Deitrick

Tim,

A lot would depend on your sampling rate and your noise to signal ration:
both together would determine the "filter" that you need to apply to your
data.

That said, it is a whole lot easier to look for crossing zero rather than
for peaks, and will yield an identical result.

Let's say that your times are in column A starting in A2, and your values
are in column B (with labels in row 1).

The formula:

=SUMPRODUCT(((B2:B1000)>=0)*(B3:B1001<0))/(MAX(A2:A1000)-MIN(A2:A1000))

will return the frequency.

Note the offset between the first two ranges: B2:B1000 and B3:B1001. This
'offset' needs to be increased to account for noisy data: the more noise and
the higher the sampling rate, the more your need to separate the ranges.
So, if you had an extremely noisy signal which you were reading every
microsecond, and that might require 10 readings to be reliably changed from
positive to negative values, then you would need to change the B3:B1001 to,
say, B13:B1011, or even B23:B1021 to be certain of properly identifying the
zero crossing point.

HTH,
Bernie
MS Excel MVP
 

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments. After that, you can post your question and our members will help you out.

Ask a Question

Top