this calibration 3.3 sgianl for Probe Compensation is normal ? - Page 1
Forum section: electronics / beginners

author: ammjy
author_rank: Regular Contributor
timestamp: December 12, 2019, 01:34:44 pm
content: Hello, EEVBlog users,I have a question about oscilloscope probe compensation.Please, see the attached figure.I didn't use this oscilloscope long time. model is OWON VDS3102.attached figure showing that 3.3V 1kHz siganl for probe compensation.but, as you see, before signal fall down, graph is bounce one time.is it normal ? could you give some advice ?

author: tggzzz
author_rank: Super Contributor
timestamp: December 12, 2019, 03:48:25 pm
content: If you are using a standard *10 "high" impedance probe, then the flat top indicates the probe is correctly compensated.The spike you highlight is not normal, since it looks like it occurs before the transition. I suggest you zoom in on the spike.If it disappears then it is an artefact of the scope, possibly during post-processing after capture. If it doesn't disappear then close examination might indicate the cause.

author: ammjy
author_rank: Regular Contributor
timestamp: December 12, 2019, 04:25:37 pm
content: Quote from: tggzzz on December 12, 2019, 03:48:25 pmThanks you for your kind help, Mr. Tggzzz.definitely my scope has problem. and now I remember before also my scope had this problem.both two channel has same this problem from 3.3V 1kHz square wave source.I should think how can I solve it.

author: tggzzz
author_rank: Super Contributor
timestamp: December 12, 2019, 04:56:39 pm
content: What is the timebase on that screendump?Have you considered the possibility that the calibration signal is the problem? Do you have another source with a suitable edge?

author: ammjy
author_rank: Regular Contributor
timestamp: December 12, 2019, 05:30:35 pm
content: Quote from: tggzzz on December 12, 2019, 04:56:39 pmtime base was 50ns/div,yes I think so too. because, both two channel showing same problem.I have a signal generator, so I will check with it againas soon as capture the graph, I will upload here !

author: ammjy
author_rank: Regular Contributor
timestamp: December 12, 2019, 05:47:35 pm
content: Quote from: tggzzz on December 12, 2019, 04:56:39 pmJust now I've finished test with 3.3 amlitude, 1 Khz, square wave signal from signal generator.Impedance is not matched. so, it has small ringing (or over/undershot) due to impedance.I think, ringing is due to signal generator.signal generator has 50ohm impedance.my signal generator is cheap one, name is GK101.and ringing is changing depend on frequency.

author: David Hess
author_rank: Super Contributor
timestamp: December 12, 2019, 05:57:39 pm
content: The calibrator output is not always clean at high frequencies, and even if it is as with some Rhode and Schwartz DSOs, it requires a coaxial connection to the probe tip to take advantage of it. It is intended for low frequency compensation.

author: ammjy
author_rank: Regular Contributor
timestamp: December 12, 2019, 06:14:13 pm
content: Quote from: David Hess on December 12, 2019, 05:57:39 pmThanks you for the your advice

author: ammjy
author_rank: Regular Contributor
timestamp: December 12, 2019, 06:36:40 pm
content: signal generator GK101 give always ringing.actually I am not sure it is occur due to impedance or signal generator.but, anyhow definite one thing is GK101 has ringing.screenshot from ()

author: David Hess
author_rank: Super Contributor
timestamp: December 12, 2019, 09:35:34 pm
content: Quote from: ammjy on December 12, 2019, 06:36:40 pmGeneral purpose signal generators will work for low frequency probe compensation however they also commonly have poor high frequency transient response. Special "reference level pulse generators" are used for calibrating high frequency transient response.

author: ammjy
author_rank: Regular Contributor
timestamp: December 13, 2019, 01:05:53 pm
content: Quote from: David Hess on December 12, 2019, 09:35:34 pmThanks for the good advice

author: David Hess
author_rank: Super Contributor
timestamp: December 14, 2019, 03:40:26 am
content: Actually I should amend my statement as some signal generators have an awful lot of "tilt" on their square wave. But good ones have very flat square waves.One of the advantages of using a function generator for probe compensation is that a coaxial connection can be used to the probe tip yielding a very clean calibration signal. Some old Tektronix oscilloscope used a BNC connector for the probe compensation output which was really nice.