LabVIEW
Phase difference block
@konradsk98 wrote:
Hi, I'm just a new LabVIEW user, and I have a problem with searching of "phase difference" block. When I used a "search" option in function pallete there isn't this block too. I don't know which block or set of blocks can replace this one. If it's important - I have the latest LabVIEW version.
If your question related to the phase only and sine signals, then in easiest form you can use Extract Single Tone Information VI, then get phase differences as shown below:
To repeat, so we have this picture of a program and all we can really determine is a "formula" for nonlinear fitting but we cannot tell what are the dependent and independent variable and parameters. It the current form, it is not even an equation!
They use a "read measurement file" as poor mans file dialog, ignoring any output except the path which is the read over and over, repeating the same calculation ad infinitum, even though once would be sufficient (unless the file gets constantly changed by an outside process, which I doubt). It is not obvious why there are 2D arrays and we cannot tell how it is converted to dynamic data. (column? row?) because the toDDT express VI configurations cannot be seen. Most of the wires are not even aligned with the terminals so we cannot even tell what's connected to where.
How does the data look like? Can you attach two typical input files and tell us what result you would expect? i am sure this can all be done with code the size of a postage stamp!
@konradsk98 wrote:I have got a measurement data for three accelerometers, and by using algorithm Levenberg-Marquardt in Curve fitting I have to approximate this data (frequency and amplitude).
Firstly I need to import this data from Excel file to LabVIEW (I don't know why "Read and measurement data" can take only half of whole table by using tab-delimited method) and get a chart of measurement points. Later I have to set a number of iteration (1000, 10000), and put some model (amplitude characteristic - a formula).Screenshot in attachment shows example of this program. Unfortunately I'm trying to do something in this case, but there is no effects of my work. The formula has w (omega) and I know I have to correct w=2πf.
So is the frequency known or a fitting parameters? So you apparently have three signals (but you only read two files?) and from the description, they seems to be sinusoidal. You really only would need Levenberg-Marquardt if the data is heavily truncated (much less than one period) AND you have excellent initial guesses for all parameters. Nobody will ever need 10000 iterations, If Lev-Mar does not converge within much less than a few hundred, you have over-parameterization and highly correlated parameters and the result cannot be trusted.
If all data is sinusoidal, there are trivially simple ways to process the signal, as already mentioned. Of course there is an infinite number of phase shifts (2pi apart) that will be equally good solutions. If the signals are complicated, but only differ in time-shift, pairwise cross-correlation might help.
In summary, instead of throwing pictures with basically not useful information at us, show us some typical data and explain the experiment! Where are the accelerometers mounted and what causes them to accelerate? Why are there three? Does each represent an axis in 3D (x, y, z)? What are you trying to learn about the system from the results?
