Average or Peak-Detect Oscilloscope setting for this waveform.

[jabbar81]

I have attached the screen-shot of my Agilent oscilloscope screen.
The output pulses on Channel-1 has about 4 micro second pulse-width pulses (yellow).
In the figure the Mode selected is "Normal", but when i select "Peak-detect" on "Acquire mode" in oscillosope, all the pulses are shown almost having same amplitude of 350V.

So only the voltage level of the output vary with the "normal" acquire mode selection, number of pulses remain the same. Also the pulses peak volatge varies with subsiquent trigger pulses on CH-2.

My question is which mode to select on the oscilloscope NORMAL or PEAK-DETECT?

 

[keith1200rs]

You need to be careful with sampling oscilloscopes. When you slow down the timebase you can miss events if you select the wrong mode. I don't know specifically the options available on the Agilent oscilloscopes but you need to read the manual carefully to choose the best mode. I almost always run my oscilloscope on 'envelope' mode. That runs the sampling as fast as possible and displays the maximum & minimum values on the screen so glitches aren't missed. That may be called peak detect on the Agilent.

If you slow down the timebase and have, say, 500k points to display, the oscilloscope has to reduce the number of points to fit on the screen. The simplest method, possibly called 'normal' is only to display a limited number of points and discard the rest. That gives a high chance of missing glitches.

Keith

 

[Pjdd]

keith has covered the technical point nicely so I won't add anything in that respect. But I'd like to insert an off-topic suggestion if I may: The attached image is in the uncompressed BMP format and is a huge 2.25MB in size which will take a long time to download by those with slow connections. Uploading it in compressed form can make a big difference. The choice of compression format depends on the image content. This image uses only 10 different colours and PNG would be a good choice. For illustration, I've compressed it as a PNG image to a size of 8.71KB - a compression ratio of more than 250 to 1 without any loss of quality.

 

[keith1200rs]

Pjdd,

A very good point - I have edited the original post.

Keith.