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Min Max does not retain true min or max

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Min Max does not retain true min or max

Postby Scott » Thu Jun 23, 2016 3:52 pm

I am running PicoScope 6 version 6.11.12.1692 with a 5444A PicoScope.

While monitoring four power supplies to see how much they are fluctuating I see the min and max
values varying in both directions.

The help states these should retain the lowest minimum and the highest maximum but they behave
more like a moving average filter.

I have masks set on all of the supplies of 200mV and I am using the DC Average measurement function.

I believe the "Value" should be averaged by this function but the max and min should hold the extremes
of the "Value" and not be averaged as well. Is this correct?

Thanks for your time,
Scott.
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Re: Min Max does not retain true min or max

Postby Hitesh » Mon Jun 27, 2016 2:36 pm

Hi Scott,

When collecting data, the measurements table should show the maximum and minimum values encountered in the last 20 captures.

If a data file containing measurements is loaded, the table will show the min and max values for the data contained in the file.

What sort of values are you seeing that suggests that it is a moving average filter?

Regards,
Hitesh

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Pico Technology
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Re: Min Max does not retain true min or max

Postby Scott » Mon Jun 27, 2016 4:49 pm

Hello Hitesh,

Your first sentence sort of answers the question.

"When collecting data, the measurements table should show the maximum and minimum values encountered in the last 20 captures."

Every 20 measurements, the min and max are updated with the min/max values during that capture set.
This is what makes it appear like a moving average filter to me since I am expecting the min/max to
maintain the min/max from the start of capturing.
This is not a true min/max over the life of the capture, only for a very short time span.

I attached three photos showing what I am looking at.
This is simply monitoring to see the extremes a non-loaded power supply is outputting.
Since the min/max move, the true min/max are not showing.
Note the second trace "D" max value is lower than the first even though it occurs
after the first in time.
The third picture shows what the help states and what I was expecting.

Supply_Test_1.jpg
First in time


Supply_Test_2.jpg
Second in time


Supply_Test_3.jpg
Help Info


I will look into the data file and see what it shows.

Thanks for your time,
Scott.
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Re: Min Max does not retain true min or max

Postby alan » Mon Jun 27, 2016 7:25 pm

Hi Scott,

Check also Tools / Preferences / General and you can change the number of captures that the measurement statistics are calculated over.

Regards
Alan
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