I need an alghorithm to generate sinudial waveform from discrete samples>?!

[petersmith885]

I need an algorithm to generate sinoudial waveform from discrete samples>?!(ie 10sample per cycle )
we have a protection Digital current Relay that samples discretely...
i need the continuous waveform of that current...
how can i do that?:grin:

 

[chuckey]

You are going to generate sine waves, so that is what your current waveform will look like! Do you want to measure frequency?, amplitude?, you know it should be a sine wave but there could be something else as well?. Are your samples locked to the waveform? What form do they take, mean value of each 36 degree period, 1 micro second sample of a 10 Hz period signal? Are they BCD measured results at logic level or analogue voltages?.
Frank

 

[petersmith885]

you know.,,,the amplitude of this signal is decreasing by the time,but the frequency is constant,the samples are locked into the waveform and we take the samples by the time intervals and the samples are value of each point...
at all i need the wave form,to measure it's decrease rate....
i need the continous form because,the discrete form will generate impulses when diffrentiating...

 

[FvM]

To reconstruct a sampled waveform in the analog domain, you have to apply a low-pass filter that keeps the Nyquist-Shannon criterion. If you however intend to process it in the digital domain at a higher sample rate, you need an interplation filter for the rate upconversion. Your question hasn't been clear about the intended action.

 

[chuckey]

If you apply these measurement to a microprocessor and store 10 successive values then compare each value with the 11th, 12th etc then you can see if the new values are greater or less then the previous. Apply a correction factor of the arc sine of the values position and each result in terms of ration should be the same and can be displayed directly. For instance, 7th sample value = 78% (of max), 18th sample measured at 76% so the signal has decayed by a factor of 76/78, but the arcsine of this sample should read .8 so the value as read should be 76/78 X 1 / .8.
If you have a local sine wave oscillator which you can phase lock to the incoming wave form if you have an compare its amplitude to the incoming waveform, driving an ALC circuit to control its amplitude, then as the incoming sine wave changes in amplitude the error voltage will try to change the amplitude of the local sine wave to keep it the same and can be calibrated in terms of % amplitude error.
Frank