Questions tagged [measurement]

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36
votes
5answers
36k views

Determining the mean and standard deviation in real time

What would be the ideal way to find the mean and standard deviation of a signal for a real time application. I'd like to be able to trigger a controller when a signal was more than 3 standard ...
14
votes
1answer
291 views

Deconvolving the measurement system from the system response

I'm preforming a system identification measurement, and would like to deconvolve the measurement system's response from the measured response. The set up of the system is as follows; the signal is ...
14
votes
1answer
1k views

Kalman Filter - Optimal Way to Handle “Derived” Measurements?

Ie, if you have as state variables position (p) and velocity (v), and I make low-frequency measurements of p, this also indirectly gives me information about v (since it's the derivative of p). What ...
12
votes
3answers
6k views

How to detect “fast” changes in signal processing

I'm working on a project where we measure the solderability of components. The measured signal is noisy. We need to process the signal in real time so that we are able to recognize the change that ...
8
votes
2answers
404 views

How to measure the quality (or difference in quality) of different images?

I would like to measure the quality of a color image, possibly as a difference to another image, but if possible, on its own too. This question comes from the fact that we have a vision application, ...
6
votes
1answer
622 views

Compare image segmentation approaches

I've got a question related to a comparison of image segmentation algorithms. I'd like to compare two algorithm results to each other in step one. In another step I'd like to compare the two ...
5
votes
2answers
62 views

Finding filaments in high dimensional space

I have unit vectors in a high-dimensional space (~300) that are non-uniformly distributed over this hypersphere. There is physical meaning when the vectors are clustered together, but I'm ...
5
votes
1answer
307 views

Received Morse Code signal-to-noise ratio?

I have some digital recordings of some received over-the-air CW broadcasts of known plain-text (W1AW code practice) at known WPM code speeds, but in moderate to heavy RF noise and fading. Can I ...
5
votes
3answers
726 views

Measuring non-planar objects in image

I'm working on a computer vision application (using openCV) and the goal is to measure the width of an object before/after it falls on a container. So after the fall its position will be random, ...
3
votes
1answer
1k views

Measuring signal phase difference between receivers

I am working on a project which aims to locate a transmitter. I consider doing this using several receivers and measuring the phase differnces between them. My problem is that arduino measures once ...
3
votes
0answers
272 views

Phase response of S11/S22 parameter for an RF attenuator? [closed]

I am new into the RF measurements. I was measuring the S11/S22 (reflection) parameters of an RF attenuator (with different attenuation levels, e.g., 10 dB) via a vector network analyzer from Rhode &...
3
votes
0answers
2k views

How to convert raw pulse sensor data into actual pulse?

I've built a simple device, which sends readings from a pulse sensor to a PC. I get these data: What technique or algorithm can I use in order to calculate the pulse rate (beats per minute) from ...
2
votes
1answer
1k views

What's the Difference Between UQI and SSIM Measures for Image Similarity / Quality?

I'm studying image quality assessment (IQA) problem and I'm currently learning about quality measures UQI and SSIM, I know UQI is a predecessor of SSIM, but they look exactly the same for me...
2
votes
1answer
85 views

Is fft2 in MATLAB unitary? Some differences happen

I meet a problem when implementing fft2 in MATLAB. The question is I try to simulate the realistic measurements $Y = |FCXF^H|^2$ - the intensity of Fourier domain of object $X$, where $F$ denotes ...
2
votes
1answer
802 views

Adjustment of window length with sliding/moving RMS method for frequency drifts

I'm using a sliding RMS mechanism to compute RMS of a signal, i.e. with a window size of N, I add the squared value of the new sample $x[n]$ to the running total while deducting the squared value of ...
2
votes
0answers
169 views

Digital filter for sharp impulse in data

I am looking for an algorithm or a filter to remove sharp peaks from my data. I am collecting raw data after every 1 second from an sensor through an ADC. The ADC has an internal FIR filter. I use ...
2
votes
1answer
426 views

Digital Vs. Analog Phase measurement [closed]

I'm working on a Ultrasonic Transducers resonance tracking system. Where phase shift between Voltage and Current is the feedback signal for my system when phase difference is Zero that means system is ...
1
vote
3answers
367 views

How to calibrate a signal with respect to frequency

I have recordings from accelerometers (non-flat response with respect to frequency) and I'd like to convert my voltage time series into acceleration values. Is there a standard method for doing this? ...
1
vote
1answer
46 views

Separability vs. Resolution - Synonymous terms?

In terms of discrete representation of a variable, let's say time measurements in absolute values in [seconds], is there a difference between separability and resolution? When do speak of either ...
1
vote
2answers
298 views

Why these harmonics always present?

I am using Audio Precision 2700 to test some test vectors. I have connected resistor banks as class - d power amp's load, and tap from this resistor using a XLR cable to the AP. When my power amp is ...
1
vote
1answer
623 views

Accuracy of Goertzel algorithm for measure harmonic

If I use Goertzel algorithm for calculate the magnitude of current or voltage, use for measure current harmonic or voltage harmonic or fundamental component. I not use for detect harmonic. Do you know ...
1
vote
1answer
34 views

Why use complex envelope to model raw measurements?

The usual answers when asking "why use complex numbers to model measurements?" is usually: (a) Because you are measuring a phenomenon like electricity and magnetism. (b) Because it is super ...
1
vote
2answers
97 views

Proof that spectrum analyzer measures mathematical Power Spectral Density

It seems to me the power spectral density (PSD) is defined as follows. Consider a signal $X(t)$ The windowed version of this signal is Consider a signal $X(t)$. We defined a time-windowed version of $...
1
vote
1answer
323 views

Can I use SINAD for THD+N measurements? Are they inverse of each other?

I'm looking for a clarification, which I haven't really been able to find. It's probably obvious but I'd like to be absolutely sure of what I'm calculating. I noticed that the formula that calculates ...
1
vote
1answer
156 views

Sensor rise time compared to experimental step input rise time

I have a dynamic calibration system. With it, I am applying a experimental step input to a pressure sensor. The goal is to measure the step response of the sensor and use it to calculate the frequency ...
1
vote
1answer
164 views

Calculating THD where peaks are not exact harmonics

I have captured an FFT of a 1 kHz signal that I am generating using a WM8904 codec running at 48k samples/second connected via I2S to a ARM microcontroller (Atmel SAME70). It appears to have some ...
1
vote
1answer
362 views

How to calculate the entropy of random normally distributed samples?

I have a hardware device that outputs a normal distribution of readings. It's (fitted) parameters are mean = 35 units, std.dev. = 8 units and I read the values as 8 bit integers. I'm trying to ...
1
vote
1answer
352 views

Best reference for object size estimation in an image

I'm working on a project where I need to measure the size of a 2D object on a flat surface from an image. I have total freedom to create a reference with any shape and size. The camera I am using is ...
1
vote
2answers
1k views

Digital low-pass filters; best practice application

I have time domain strain gauge data from a structure which is subjected to low frequency, random loading. The signal / noise ratio is pretty good, but I would like to try to improve on it as much as ...
1
vote
0answers
36 views

How to determine number of observations based on measurement frequency?

So I'm working on a problem where I'm measuring a signal with two different instruments -- one is a low frequency measurement system (1 Hz), and the other is a high frequency measurement system (200 ...
1
vote
0answers
67 views

How to draw a smooth spectrum from a discrete array of measurements at selected frequencies?

I have a AS7265x triad spectroscopy sensor from SparkFun (link) which gives me measurements at 18 individual light wavelengths between 410nm and 940nm. The datasheet says that the FWHM of each sensor ...
1
vote
0answers
98 views

Calculating Transfer Functions From Harmonic Distortion Percentage

Hi I am working on emulating a piece of analog audio equipment and would like to be able to create a transfer function based on the measured percentages of harmonic distortion. I know that harmonic ...
1
vote
1answer
112 views

Filter results from force measurements

I was provided with several force measurements. Precisely: The vertical compression force exerted from the milling tool on a working peace. The plot of the force looks reasonable and of course it ...
1
vote
0answers
48 views

How does the error in azimuth angle vary as one moves away from the boresight direction of a radar

My question is basically same as the title. I am trying to find a mathematical model which provides the error, $d\theta$, in azimuth angle($\theta$) as one moves away from the boresight direction of ...
1
vote
0answers
45 views

Parameter estimation from a measure

I'm doing an exercise where, given a data sample taken from a physical measure, I have to estimate the parameters of the measure where samples $x_i$ are described by the equation: $$ x_i = A \sin(2\pi ...
1
vote
0answers
72 views

Why is the term deconvolution used more for signals and not so much (or at all) for systems?

Wikipedia defines mathematical deconvolution here, and with the examples given and my experience, what I've read over the years is that deconvolution is used to determine an input signal provided a ...
1
vote
0answers
624 views

Sampling and zero crossing

I am sampling a sine wave of 50Hz(stepped down from 230V) at the rate of 500KHz. For identifying disturbances in the wave, i was thinking of comparing a cycle of incoming sine values with reference ...
1
vote
0answers
18 views

How is per-class rate defined?

I've recently read the following For our pixel labeling, consistent with [20], we report the number of pixels correctly classified (per-pixel rate) and the average of per-class rates. The per-...
1
vote
1answer
40 views

Accurate measurement of object's position on a bayer-filtered and grayscaled images

This is an experience-related question about cameras and image processing. I have a laboratory setup. Under some simplifications it looks like a red ball rolling on a white table (the real setup is ...
1
vote
1answer
528 views

Measuring the similarity of two waveforms [closed]

I have two approximately sine truncated waveforms of different amplitudes and I want a numerical measure of how similar they are to each other. I am sending a sonic pulse train whose multiple ...
1
vote
0answers
154 views

Image objects dispersion and diversity measures

I have images like below: I want to find some measures describing black spots dispersion and diversity. First measures I use are mass center off all black spots, mean area of spot, stdev of area ...
0
votes
3answers
126 views

Quality of experience engineer

I have noticed certain overlap between digital signal processing and quality assurance for jobs that require expertise in evaluating the quality of the transmitted signals on telecommunication systems ...
0
votes
2answers
393 views

Measuring amplitude of a spectral component

I'm trying to measure the amplitude of a spectral component in a signal. The component's frequency is always known beforehand. I take a given number of samples, apply the flattop window to reduce ...
0
votes
1answer
31 views

how to get the location long and lat out of the raw measurements?

I'am making a research about GNSS I used GNSS logger to collect measurements but couldn't understand how these measurements turn into location of long and lat? the picture below of the measurements ...
0
votes
2answers
27 views

Using the traditional instruments for measuring high frequency signal

All we know that we can not use the probe for measuring the high-frequency signal (microwave signals). I still can not understand the reason. I have read that the reason because of the wavelength size ...
0
votes
2answers
486 views

measure angle between two lines, can rotation center constraint be used to refine the initial measured result?

I'm trying to measure the angle between two needle positions in an analog meter (gauge). such as: After the image processing of several images, I get the processed image below(a image show different ...
0
votes
1answer
65 views

Can I measure non-linearity of a line echo path?

I'm dealing with an echo signal from a hybrid. An echo path includes DAC, the hybrid, ADC and the line infrastructure. I can see, that after using a digital linear echo-canceller the residual echo ...
0
votes
1answer
35 views

Oversample or undersample correlated noise?

I wish to measure nontrivial (non-Gaussian) broadband current noise for its distribution and power spectral density. The noise is amplified (with transimpedance amplifier) with some characteristic ...
0
votes
1answer
77 views

Measuring THD using consumer sound card

I am trying to measure (estimate) THD of an audio path using a consumer sound card. The idea is that I do two measurements, one without the system being measured in the path and one with it: ...
0
votes
1answer
52 views

Phase difference measurement of a 100 kHz tone

I would like to measure the phase difference of a 100 kHz tone. The tone is transmitted and then received. The received tone is sampled using an 1 MHz 12 bit ADC(IQ) and the SNR is at least 35 dB. ...