script Derivation & Integration engine

[lab!fyi]

Hi, since forum search did not yield much on subject and there seem to be no built in functions did write little something and decided to share below:

Script is quite automatic. It will account for sampling rate, memory depth, oversampling changes in real time - just run it to auto create and configure Ref* channels that will display functions. Possible need fiddle Range a little for integration. If wish reset to auto values just disable/delete Ref* and it will instantly re-enable in default configuration. Attached script is provided in demo mode, does integral(derivative(x)) functional check and integral(x). Unneeded doMath*() stuff can be commented out in main() function. If wish for derivative to start from 0 (currently it will remember DC offset for later signal reconstruction) set bDerivativeRetainsDCOffset = false; 

Code that accounts for Time changes is quite generic so script can be easily expanded with other doMath*() routines.

Code tested on: WaveForms version 3.8.10 beta 64-bit Qt5.6.3 Windows 7

// Derivation/Integration for WaveForms, v0.1
// By lab!fyi <info@lab.fyi>
// http://lab.fyi/oscilloscope_scripts/derivation_integration/index.html
// This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

// Uncheck or delete Ref[1|2] in Run mode to reset units to automatic values

// Config
bDerivativeRetainsDCOffset = true;
oChannel = Scope1.Channel1; // Used for Ref config detection

// Derivative >>>
function _derivative(aIn, aOut)
{
    aOut[0] = 0;
    if (bDerivativeRetainsDCOffset)
    {
        aOut[0] = aIn[0] * iSTRate;
    }
    for (var i = 1; i < aIn.length; i++)
    {
        aOut[i] = (aIn[i] - aIn[i - 1]) * iSTRate;
    }
}
function derivative(oIn, oOut)
{
    var aO = oOut.data;
    _derivative(oIn.data, aO);
    oOut.data = aO;
}
// <<< Derivative

// Integral >>>
function _integral(aIn, aOut)
{
    var f = 0;
    for (var i = 0; i < aIn.length; i++)
    {
        f += aIn[i] / iSTRate;
        aOut[i] = f;
    }
}
function integral(oIn, oOut)
{
    var aO = oOut.data;
    _integral(oIn.data, aO);
    oOut.data = aO;
}
// <<< Integral

// Config >>>
function getSTRate()
{
    return Scope1.Time.Rate.value * (oChannel.data.length / Scope1.Time.Samples.value);
}

function config(oIn, oOut, fScale)
{
    if (!oOut.enable || !oOut.checked || bInit)
    {
        oOut.setEnable(true);
        oOut.checked = true;
        oOut.Clone(oIn);
        oOut.Range.value *= fScale;
        print
        (
            "(Re)Enabled/Checked & Cloned "
            + "'" + oIn.name + "'"
            + " -> "
            + "'" + oOut.name + "'"
        );
    }

    if
    (
        (oOut.data.length != oIn.data.length)
        || (iSTRate != getSTRate())
    )
    {
        var iRange = oOut.Range.value;
        var iOffset = oOut.Offset.value;
        oOut.Clone(oIn);
        oOut.Range.value = iRange;
        oOut.Offset.value = iOffset;
    }
}
// <<< Config

// ------------------------------------------------

function doMath1(oIn, oOut)
{
    config(oIn, oOut, iSTRate);
    derivative(oIn, oOut);
}

function doMath2(oIn, oOut)
{
    config(oIn, oOut, (1 / iSTRate));
    integral(oIn, oOut);
}

function main()
{
    if (!('Scope1' in this))
        throw("Please open a Scope instrument");

    Scope1.run();

    iSTRate = getSTRate();

    while (Scope1.State.value == 6) 
    {
        while (Scope1.wait())
        {
            // integral(derivative(x))
            doMath1(Scope1.Channel1, Scope1.Ref1);
            doMath2(Scope1.Ref1, Scope1.Ref2);

            // integral(x)
            doMath2(Scope1.Channel1, Scope1.Ref3);

            bInit = false;
            iSTRate = getSTRate();
        }
    }
}

// ------------------------------------------------

bInit = true;

main();

Scope1.stop();

 

derivation_integration.dwf3script

[lab!fyi]

Forgot to mention little problem. It seems to be no counterpart for Oversampling setting in Scope1.Time object. Had to use some workaround to get the setting value.

[attila]

Hi @lab!fyi

Thank you for sharing this.

Could tell a bit about the use of this script and post some screenshots?