High Pulse Width measurement

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PedroWeb
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Joined: Thu Mar 09, 2017 11:39 pm

High Pulse Width measurement

Post by PedroWeb »

Hi,

I'm using PicoScope to measure the CPU time. I was relaying on the automatic measurement to get the worse case scenario (Max High Pulse Width) but after analyzing the traces I noticed that the automatic measurement is not working as expected (Please see screenshot below)

I'm measuring with the cursor 70.35us however the max value is 63.28us reported by the automatic measurement.

I'm using the PicoScope version 6.1.2.7.2687 and HW 5444B.

Does anyone got the same problem?

Am I doing something wrong?

Thank you in advance for your help
Attachments
HighPulseWidth.png

Martyn
Site Admin
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Location: St. Neots

Re: High Pulse Width measurement

Post by Martyn »

High Pulse Width Measurement: The amount of time that the signal spends above its mean value. This is the average value for all the pulses in a waveform that have a rising edge, when Whole Trace is selected, or related to the rulers if one of the other options is used.

So the readings you are seeing look to be correct.

The terms in the table can sometimes cause confusion, they are :-

Value - The value for the buffer on the screen

Min, Max, Average - These are averages for the number of buffers specified by the Capture Count, and not for the single buffer on the screen. The Capture Count can be set in Tools->Preferences->General
Martyn
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lightning_doc
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Joined: Mon Nov 20, 2017 12:58 pm

Re: High Pulse Width measurement

Post by lightning_doc »

Hello,
in our filed (high voltage/current impulse testing) we measure the pulse widths as the full width at half maximum (FWHM), i.e. the distance between points on the curve at which the variable reaches half its maximum value.
Is there a way to program this kind of measurements ourselves, or to include it as a standard measurement to the picoscope software?

Thanks

Martyn
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Joined: Fri Jun 10, 2011 8:15 am
Location: St. Neots

Re: High Pulse Width measurement

Post by Martyn »

It is not possible to add a custom measurement using our PicoScope 6 software, so I will pass the information on to the development team for consideration.
Martyn
Technical Support Manager

lab!fyi
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Joined: Mon Dec 12, 2016 6:58 pm

Re: High Pulse Width measurement

Post by lab!fyi »

Following may be of some use if want to have arbitrary and fixed ref level for measurements w/o configuration like Pulse Width, Duty etc: In this example ref level is set to 0V, so can be steered around on real signal with DC offset (or additional math).

Clip signal -100mV...+100mV:
((abs(A-0.1)-(A-0.1))-(abs(A+0.1)-(A+0.1)))/-2+0.1

Some other potentially useful functions:

Extract positive part from signal:
(-abs(A)+A)/-2

Extract negative part from signal:
(abs(A)-A)/-2

As can see LowPulseWidth(Clip) matches cursors on zero level.
Attachments
signal_clipping_math.jpg

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