translation into sine wave

[boldfish]

I have a reciprocating test table connected to a DAQ that outputs position sampled at the rate of 20 samples per second.

The positional output is a range of values from 0 to 20 and over time a sample of 10 cycles is normal.

I would like to graph this set of data in the form of a sine wave; 0 and 20 correspond to the points where the graphed line crosses the x axis and the peak of the sine wave is at 10 and -10.

I'm struggling and need some help. Can anyone suggest a formula for translating this data?

 

[MintJulep]

What?

You can only graph something as a sine wave if it is a sine wave.

Otherwise the graph will look like whatever it is.

 

[RWF7437]

What is A "DAQ" ?

What are you trying to do ?

If you have data of amplitude vs. time, why not simply plot it ? If it looks like a sine wave it probably is but you can test this by also plotting a sine wave alongside it.

You say "The positional output is a range of values from 0 to 20 and over time a sample of 10 cycles is normal." (sic)

But elsewhere you say the range is from -10 to +10. Which is it ?

good luck

 

[Denial]

If you are trying to establish the "sine wave of best fit", you can use Excel's "Solver" to minimise the squared errors (or any other measure of error that you might prefer).

 

[boldfish]

A DAQ is a data aquisition system. The one I am using is some variation of WINDAQ.

The output through the DAQ is simply a set of numbers ranging from 0 to 20 (position of the table in inches). As the table cycles, the numbers increase from 0 to 20 and then decrease from 20 to 0 and repeats.

I'm not looking for an exact sine wave. I just need a sine wave shape (which this data does produce). However, I need the shape to be shifted so that the 0 and 20 values correspond to 0 (crosses the x axis).

The area of interest is when the table is moving. There is no significant occurence at 0 or 20.

I guess what I really need is the plot of velocity.

Thanks anyway.

 

[MintJulep]

Your data recorder gives you point pairs of time and position, yes?

Velocity is the first derrivative of position.

 

[IRstuff]

so subtract 10 from all the values to center them

derivative is delta_pos/delta_time

TTFN

FAQ731-376