Prosig Noise & Vibration Measurement Blog » spikes

Interpolation Versus Resampling To Increase The Sample Rate

Dr Colin Mercer — Mon, 22 Jun 2009 14:12:21 +0000

These are two different techniques aimed at different objectives. First consider a simple sinewave that has been sampled close to the Nyquist frequency (sample rate/2).

Visually this looks very pointy. We will examine it using a filter based interpolation and a classical curve fitting procedure to obtain a better representation.

As a second example we will look at a [...]

Cleaning Up Data

Dr Colin Mercer — Mon, 22 Sep 2003 14:17:08 +0000

When we have a very noisy signal with a large number of spikes and signal bursts then if all else fails try Median Filtering. This is a technique often used in cleaning up pictures. The operation is almost childishly simple in concept but we will save the [...]

Data Smoothing : RC Filtering And Exponential Averaging

Dr Colin Mercer — Mon, 28 Apr 2003 15:18:11 +0000

What are RC Filtering and Exponential Averaging and how do they differ? The answer to the second part of the question is that they are the same process! If one comes from an electronics background then RC Filtering (or RC Smoothing) is the usual expression. On the [...]

Smoothing Spectral Data

Dr Colin Mercer — Mon, 15 Jul 2002 16:23:56 +0000

Sometimes data has spikes which are clearly artefacts of the processing or are due to some other external source. One is used to seeing these on time series but in some cases there are unrepresentative “spikes” in the frequency analysed data. An example spectrum is shown below.

Figure 1 Spectrum with False “spikes”

There are [...]

Don’t Let Spikes Spoil Your Data

Dr Colin Mercer — Wed, 06 Jun 2001 16:50:06 +0000

In many real-world applications it is impossible to avoid “spikes” or “dropouts” in data that we record. Many people assume that these only cause problems with their data if they become obvious. This is not always the case. Consider the following two time histories.

Figure 1: Signal containing "spikes"

Figure 2: Signal with "spikes" removed

To the [...]

Getting Rid Of Spikes

Dr Colin Mercer — Wed, 06 Jun 2001 07:38:46 +0000

For various reasons data captured in the real world often contains spikes that will give erroneous results when analysed. DATS for Windows provides various ways of editing and removing these anomalies. Let us consider a real life case history.

Fig. 1 : A sine wave with two obvious spikes before and after 'de-spiking'

A large aerospace manufacturer [...]