frequencyrange dependant Ripple & Noise Measurement possible ?

[Rolf_K]

Hello,
is there a frequencyrange dependant Ripple & Noise Measurement possible ?
We need to measure the follwing according IEEE802.3at for PoE Powersupply Voltage Requirements:

• f<500Hz:              max. 0.5 Vpp
• 500Hz-150kHz:    max. 0.2 Vpp
• 150kHz-500kHz:  max. 0.15 Vpp
• 500kHz-1MHz:     max. 0.1 Vpp

This might be possible via script ...
if yes, could you give an example ?
Or is there a other solution ?

[attila]

Hi @Rolf_K

I don't know exactly how do you want to measure it but with Spectrum you can use the Logging view or Script like this:

Spectrum.run();
while(wait()){
    var hz = Spectrum.Trace1.frequency;
    var mag = Spectrum.Trace1.magnitude;
    var c = hz.length;
    for(var i = 3; i < c; i++){ // 3 to skip DC
        if(hz[i]<500 && mag[i]<0.5) continue;
        if(hz[i]<150e3 && mag[i]<0.2) continue;
        if(hz[i]<500e3 && mag[i]<0.15) continue;
        if(mag[i]<0.1) continue;
        Spectrum.stop();
    }
}

 

Edited December 5, 2022 by attila

[Rolf_K]

Hi @attila,
thanks a lot for your answer !
I talked with some colleagues to clarify the measurement setup:
The measurement result should be the same as
if you create the 4 filters in hardware and measure the peak to peak Voltage in time domain with the scope !
So a possible solution could be an inverse FFT with the filtered  4 frequency ranges,
and then measure the peak to peak voltages for each of the 4 frequency ranges in the time domain
( i assume this results in the same as the hardware filter).
Is that posible (especially an inverse FFT) ?

Edited December 7, 2022 by Rolf_K

[attila]

Hi @Rolf_K

IFFT is not available here but you could make use of a filter channel, a script which changes the sample rate and adjusts the filter parameters for freq ranges, uses pk2pk measurement for testing.

[Rolf_K]

Hi @attila,
thanks a lot for your answer ! 👍
I try to figure out, which filtertype fits best:
Butterworth, Chebychev or Custom !
(Custom in the help is not good explained ...)
 

Edited December 9, 2022 by Rolf_K

[attila]

Hi @Rolf_K

Probably Butterworth