Resolution enhancement and trigger threshold

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shlllink
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Resolution enhancement and trigger threshold

Post by shlllink »

Hi all,

I am using a Picoscope 3206D and Picoscope 7. I used the resolution enhancement to increase the resolution from 8 to 12 bits. When taking data with a 500 mV trigger threshold, I noticed that there were quite a few events below 500 mV that were recorded.

I know that resolution enhancement employs a flat moving average filter, but I'm not sure why this would cause events below the trigger threshold to be saved.

I believe an extra 4 bits of resolution means that 256 pulses are averaged together. Is it possible that only a single pulse out of 256 needs to be above the trigger threshold, and then the averaging process can lower the amplitude of the pulse before saving it?

Martyn
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Re: Resolution enhancement and trigger threshold

Post by Martyn »

Resolution enhancement is applied post capture on collected data in the PC. Triggering is performed on the original data in the PicoScope.
Martyn
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shlllink
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Re: Resolution enhancement and trigger threshold

Post by shlllink »

Thanks for the clarification.

That would mean that the scope was just recording events that occurred below the trigger threshold. This can be seen by looking through the waveforms. I can see pulses as low as 300 mV even though I set the trigger threshold to be 500 mV.

I this normal behavior? I've never seen this occur before I tried using the resolution enhancement. That's why I thought there might have been some connection.

Martyn
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Re: Resolution enhancement and trigger threshold

Post by Martyn »

Can you post psdata files showing what you mean, then we can see the actual data and the setup of the scope and software.
Martyn
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shlllink
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Re: Resolution enhancement and trigger threshold

Post by shlllink »

Certainly. This is only half of the traces. The whole file was too large.

Waveforms # 24, 44 and 58 are examples of what I'm talking about, though there are many others.
Attachments
20240223-0004 half.psdata
(4.94 MiB) Downloaded 17 times

Martyn
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Re: Resolution enhancement and trigger threshold

Post by Martyn »

If you remove the resolution enhancement so that you are seeing raw values, you will see that every trigger is actually at the same value of 471.2mV as shown by the masurement I have added which is maximum between rulers.
TriggerPoint.png
this applies to the buffers you mentioned but also ones which clearly pass through the trigger point, as per this buffer
TriggerPoint2.png
This is below the 500mV because you also have applied a zero offset of -23mV to the signal.
You don't get an exact 500mV as the scope will have applied digital scaling to ensure that it meets the published specifications.

If you wish to make sure that the signal passes through the trigger point and not just reaches it, I would change the trigger type to advanced edge, and add in more hysteresis.
Martyn
Technical Support Manager

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