# Option SCAN down to 1ms?

Hi guys,

i could really need the “Realtime-Scan” from 1-100ms. I already contacted BenF for this, but he said post it in the forum, so i did, and now i need you guys to help me to convince him to put this in (it also would’nt be much work i guess ) .
I have to check a signal (square-signal) for single missing parts, that has about 200Hz. With AUTO it takes to long to reload the screen so i would not see those missing parts. Too sad that SCAN only works with 100ms and up.

Ben said to me that the eyes could not follow the wave below 100ms, but i say this is wrong. I can see the swiping of the wave down to 20ms. A realtime sweep of the screen with 10ms/DIV would take about 120ms. Thats like 8 Frames per second which actually less than 12 FPS which makes the eye see a motion. You might have seen those oldstyle Movies where u can see the dirt spots on the film.

I think the SCAN is useful down to 2ms (if the refresh rate of the screen is like 30 FPS). Changes in a not moving signals are easy to see, and i would bet you could see changes of a signal with a refreshrate of 40FPS. At 50ms/DIV it takes like ages to redraw the wave, and this annoyes me really when i want to see how the signal is behaving in realtime!

Is there anyone else that thinks the same?

Cheers Toby

I think I understand what you ask for, but I’m still not sure why you want this change. You leave me to guess and the usage I envision does not make a lot of sense to me.

A 200Hz signal has a time period between cycles of only 5ms and if (the guessing part) this signal of yours is a steady pulse train (digital square pulses), you will have one pulse for every 2.5ms. This is the equivalent of 400 unique lows and highs every second. If (more guessing on my part) your idea is to display these pulses (using scan) and look at the screen to see if one is missing, you don’t stand a chance. 400 pulses is just too much to comprehend every second and they will also be phase shifted (the edges will not appear at the same position of the display because scan is not triggered) making it a complete mess to watch.

The common solution to a problem like this is to use a pulse trigger. That is to let the scope scan continuously (no display) until it finds a pulse which meets trigger criteria (such as width larger than some user defined value) and only then stop to display the result. You set up the pulse trigger and leave the scope running for several minutes and if it triggers, you know you have an issue. In terms of digital analysis this is about as simple as it gets, but still not supported by the Nano. A logic probe will have a lot more to offer in this respect and possibly this is what you really need.

I want this for detecting failure of signals in cars.

Yes at 200Hz the timeperiod ist 5ms, BUT i would set up 5ms/DIV which results in a waveformrefresh (the screen has 12 DIV -> 60ms for screenrefresh) of 17 Frames per second. Remember: At 12 FPS the eye starts to see a continues motion.

Perhabs its even possible to watch a 400Hz signal, but then you gotta be more focused.

I wrote a little OpenGL program to see what ms are like. I can see 16ms “spikes”. Therefore i think it is possible to watch almost 1KHz, but only with focused attention on the screen (if the screen has 60FPS).

For anyone interested, i attach the program and the source!

What is the actual refresrate of the screen of the nano v2??
16ms_60FPS.rar (8.03 KB)