I am trying to get rid of spikes of noise in a sinusoidal signal...

See attached picture (a snipet of the signal) to see what I am talking about.
I would like to get the index of the maximum and minimum points for every second, but these random spikes are interfering with the measurement.
I tried using the median filter vi with ranks of 5 for right and left (I tried values from 1-10, and 5 worked the best), but this has caused problems with the index calculation (the index is higher than it should be based on the graph).
Any ideas on a different filter I should be using? Or am I making an error with the median filter vi?
Attachments:
signal with noise.JPG ‏57 KB

Okay, Lynn, you made me look it up.
For a low pass filter (analog), the phase shift is:
, where w is the filter center frequency and w(0) is the signal frequency (can't do omegas here, I guess).
So, for a 50 Hz filter on a 1 Hz signal (pretty much what the picture shows), the phase shift is 1.14 degrees or 3.18 milliseconds, whatever number of data points that comes out to in the sampling rate Laura121 is using.
I thought about a Savitsky-Golay filter, but it looked like the amount of calculating it would take would not be worth any possible advantages. YMMV.
Cameron
To err is human, but to really foul it up requires a computer.
The optimist believes we are in the best of all possible worlds - the pessimist fears this is true.
Profanity is the one language all programmers know best.
An expert is someone who has made all the possible mistakes.
To learn something about LabVIEW at no extra cost, work the online LabVIEW tutorial(s):
LabVIEW Unit 1 - Getting Started
Learn to Use LabVIEW with MyDAQ

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