Detection of peaks on a Log Scale.

[Capillod]

Hi there
I am using a DAQ card to detect the amplitude voltage of a circuit. The output voltage is vairying and i want to detect the peaks. The chart has many peaks e.g. 20 peaks each one slightly smaller than the previous one.
I have tried using the Advanced Peak Detector PtByPt vi. but i am getting some strange results.
It seems to detect the first 4 or 5 peaks no problem but any subsequent peaks give strange results.
The peroid of the changing voltage is about 20 seconds.

Any suggestions???


Please see the attached file.

Thanks
Capillod

[SciWare]

Hi Capillod

One thing to keep in mind is that the location that the peak detector outputs is a fractional index of the internally held data buffer so you will need to calculate from the fractional index the real location. The calculation is

PeakLocation = Fractionalindex – SampleLength + x

I’ve attached a demo that simulates a spectrum and passes it point by point into the Advanced Peak Detector PtByPt.vi this will allow you to simulate your system and fine tune the peak detection.

Good Luck

[astroboy]

Hi  May I have these downloaded files in version 7.0?

Many thanks in advance.

Clement

[SciWare]

Hi Clement

Sure, no problem.