ETS amplitude differences

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PatrickSmeets
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Joined: Mon Nov 02, 2020 1:31 pm

ETS amplitude differences

Post by PatrickSmeets »

I'm measuring a repeating 350kHz block wave signal in ETS mode.When the sample interval is set to 1ns (1Gs/s), the waveform shows the correct amplitude of about 11V.
ETS_1ns.png
When changing to 400ps sample interval (2.5Gs/s) or smaller, the amplitude drops to 10V.
ETS_400ps.png
Did anybody encounter the same behaviour? Any suggestions?

Gerry
PICO STAFF
PICO STAFF
Posts: 929
Joined: Mon Aug 11, 2014 11:14 am

Re: ETS amplitude differences

Post by Gerry »

Hi Patrick,

This scaling of just over 10% is, indeed, what happens, consistently, to the amplitude of a real-time sampled waveform, when switching to an Extended Time Sampled waveform. I'm about to take a break, but I'll look into this further for you when I return.

Regards,

Gerry
Gerry
Technical Specialist

PatrickSmeets
Newbie
Posts: 0
Joined: Mon Nov 02, 2020 1:31 pm

Re: ETS amplitude differences

Post by PatrickSmeets »

Hello Gerry,

Meanwhile, did you make any progress on the issue? Maybe you have suggestions for a possible work-around.

Kind regards,
-Patrick

Gerry
PICO STAFF
PICO STAFF
Posts: 929
Joined: Mon Aug 11, 2014 11:14 am

Re: ETS amplitude differences

Post by Gerry »

Hi Patrick,

I've only just returned, so looking at this closer, it applies to all Timebases less than 2u s/div irrespective of sample count, input range, and signal source & frequency (Bit resolutions other than 8 are not applicable to ETS Mode). It is also specific to the 5000 series so appears to be a bug, which I will alert our development team to.

In the meantime, the only workaround I can think of would be creating a Picosecond range custom probe, to switch to when you use ETS mode on PicoSecond sample intervals, which is below. However, be aware that the Probe will upset the neat divisions of the vertical scale which means that you can only return to the neat divisions by removing the custom probe (returning to a x1), so only use it if you want to make measurements with channel rulers that are more accurate. For best accuracy, adjust the custom probe for your specific scaling error, by measurement. So, from the signal generator, send a 1V 2MHz square wave into a +/- 2V input range, on a Timebase of 1us/div for Repeat Trigger Mode. Then set the coupling to AC, and switching between Trigger Methods, divide the Repeat Trigger peak of the square wave by the ETS peak of the square wave and use the ratio for the gradient of the Scaling Method in the custom probe.
Picosecond ETS Mode Range Adjust.psprobe
(1.09 KiB) Downloaded 44 times

Regards,

Gerry
Gerry
Technical Specialist

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