# Questions tagged [physical-units]

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### Changing units in Fourier filtering

I'm applying a radial low-pass filter on a $H{\times}W$ pixel 2D image $I$ where $H \neq W$. To implement this filter, I apply 2D DFT to $I$ to produce $I'$, the $H{\times}W$ frequency domain ...
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### Loss of precision due to low-pass filtering in physical units

Suppose I have a $10{\times}10$ pixel image, where each pixel represents 1 mm in physical units, and I apply a Gaussian low-pass filter with $\sigma = 5$. Can I make any statements such as "the ...
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### Correct way of viewing negative voltages in units of dB for noise analysis

I have a voltage signal, on top of which there is some noise. I am interested in the noise components so the way I am trying to do this is to fit the known signal to the data and look at the residuals....
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### Convolution Input/output Units

How come are the units of convolution for LTI system not consistent? $$y(t)= \int_{-\infty}^{\infty} x(\tau)h(t-\tau)d\tau$$ $y(t)$ unit is volt, whereas the RHS has volt.time unit!!!!
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### What is the difference between the PSD and the Power Spectrum?

Can any one explain the difference in the amplitude between the two and what does each one represents? For example, when using the pwelch algorithm in MATLAB how ...
### Why is “$1/\mathrm{Hz}$” unchanged while converting$\mathrm{V}^2/\mathrm{Hz}$ to $\mathrm{dB}/\mathrm{Hz}$?
When computing power spectral density via Fourier transform and Parseval's theorem, one gets units of $V^2/Hz$ (e.g. Wiki). As a popular next step, the following unit conversion is widely used: \$V^2/...