Analog voltage input to frequency

[jeffc]

I'm logging an analog input voltage and would like to convert the signal to frequency. Does anyone know if this is possible with Labview?

[Labviewguru]

Jeff(?),

Anything that is possible, is possible with LabVIEW.

Now, what exactly are you trying to do?

You have indicated that you want to convert an analog voltage, to a frequency. Frequency is a time-based signal, and is usually represented as amplitude vs. Time, such as an AC Signal. I am not sure what you are asking here. Could you please provide a bit more detail.

But really, anything is possible with LabVIEW, as long as it is possible.

[jeffc]

I'm trying to replace an old hardware (25yrs) instrument. As best as I can tell it takes the output from an accelerometer (+ or -5v) filters the signal through a band pass and then rectifies it. Now here is where i'm stumbling, the signal is changed to frequency and fed through a pulse counter to be averaged. Strange I know but the engineers only want an objective number that represents the amount of wobble, they don't care about the actual data. I think the old box actually outputs averaged acceleration divided by time (hardware triggered on and off) on a 1 to 10 scale.

The daqpad 6020E is what they are using on site now.
Any help or hints would be appreciated

Jeff C

[CraigGraham]

> through a pulse counter to be averaged. Strange I know but the
> engineers only want an objective number that represents the amount of
> wobble, they don't care about the actual data. I think the old box
> actually outputs averaged acceleration divided by time (hardware
> triggered on and off) on a 1 to 10 scale.
>
> The daqpad 6020E is what they are using on site now.
> Any help or hints would be appreciated
>
> Jeff C

Like this? Slide represents the analogue input; LV6.

--
Craig Graham
Physicist/Labview Programmer
Lancaster University, UK




[Attachment VariableFrequencySine.vi, see below]

[Hugh]

So you want to use the filtered, rectified output of your accelerometer
to drive the
input of a voltage controlled oscillator. What is the required VCO gain,
i.e. Hz/Volt?
What are the maximum and minimum frequencies?

The difficulty with using LabVIEW for this will undoubtedly be one of
generating your
waveform in real-time. You'll have to be fairly clever. Johnson &
Jennings' book, "LabVIEW
Graphical Programming" has an example of continuous waveform generation
with on-the-fly
amplitude changes (chapter 15). You need to do on-the-fly frequency
changes but this
example might be a good start.

If I was you I'd stick a hardware VCO in my instrument package and be
done with it 😉
http://www.electronics-tutorials.com/oscillators/voltage-controlled
-oscillators.htm

Hugh

jeffc wrote:

>I'm trying to replace an old hardware (25yrs) instrument. As best as I
>can tell it takes the output from an accelerometer (+ or -5v) filters
>the signal through a band pass and then rectifies it. Now here is
>where i'm stumbling, the signal is changed to frequency and fed
>through a pulse counter to be averaged. Strange I know but the
>engineers only want an objective number that represents the amount of
>wobble, they don't care about the actual data. I think the old box
>actually outputs averaged acceleration divided by time (hardware
>triggered on and off) on a 1 to 10 scale.
>
>The daqpad 6020E is what they are using on site now.
>Any help or hints would be appreciated
>
>Jeff C
>

[Oleg]

Hi,
If I've understood you correctly you are looking for an instrument to count the number of peaks in your signal. You can use "Functions/Analyze/Signal Processing/Time Domain/Peak Detector.vi" or "Functions/Analyze/Signal Processing/Time Domain/Threshold Peak Detector.vi". This VIs analyze the input array and returns the number of peaks in it.

But my experience shows that these VIs work well only for signals with big signal/noise ratio and good shape of signals. In most cases it's more convenient to write your own pulse analyzers.

Good luck.

Oleg Chutko