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DSOX1102G weird and noisy square waveform when probe tip is set to X10

Question asked by Pollaris on Aug 28, 2017
Latest reply on Sep 15, 2017 by Pollaris

I bought a brand new 100MHz DSOX1102G oscilloscope, when executing initial tests I noticed a strange behavior when I set the probe tip switch to X10 position and using probe comp/demo connectors, when I press the Auto Scale button I'm getting a weird waveform that appears an extended X like a crosstalk signal effect. If I set the same probe tip switch to X1 position and press Auto Scale I get the test square waveform perfectly.

 

I have experience with oscilloscopes, I also have a Tek TBS1102B and doing the same test with the probes provided by Keysight I get both in the X1 and X10 positions the same square waveform as expected on Keysights one, perfect !

I also noticed that the probe tip switch set to X10 on the DSOX1102G capture too much noise, much more that is noticed on TBS1102B. Despite this, noise floor apparently is within the parameters of the device.


The only way I can get the correct square waveform with probe switch set to X10 position is activating the channel BW limiter that I think it´s not normal, so the waveform is perfect and clean like as observed at X1 position.

 

Also I noticed in menu Probe Check I only get success when the probe switch is set to X1, if I move the switch to X10, the Probe Check fails with warning window indicating to connect the probe to Probe Comp terminal and probe grounding wire to Probe Ground terminal. Maybe some impedance matching problem between the probes at X10 switch position and the oscilloscope input´s circuitry ?

I tested with the two Keysight leads that came with the oscilloscope, tested with the default Tek fixed X10 probe and tested the Keysight probes on TBS1102B too. The probes are perfect and on TBS1102B everything works as expected.

This behavior occurs both on two DSOX1102G channels and only when the probes are set to X10, when are set to X1 the oscilloscope acts as should be showing a perfect test square waveform.

When I connect my Arbitrary Function Generator with BNC to BNC coax cable I have no problem, all waveforms are showed as expected with frequency and amplitude within the parameters adjusted in my AFG. Even signals of very low amplitude are observed in the same way that I see them in Tektronix. Again, oscilloscope input impedance matching issue ?

 

I would like to know if this is expected behavior for this device (I do not think so but...) whether it is a hardware faulty on my unit or a firmware problem that can be fixed in a future release.

It is sad to buy a brand new equipment from a renowned manufacturer of measuring instruments and to know that I may have errors in my analysis and measurements, a fact that has never occurred to my really basic but reliable Tektronix TBS1102B. Although I really liked the DSOX1102G and I´m very impressed by it resources but I do not know if I bought a faulty unit or not.

 

I will appreciate a reply hoping that my findings may be useful in determining what is happening with my oscilloscope and possibly other users as well.

 

I have attached some pictures demonstrating to make clear what I am saying, I apologize for any errors in my English since my main language is Portuguese and maybe I have not been clear in the translation.

 

Thanks for any comments and it would be useful too if someone can reproduce the same steps and tell me the result.

 

Cheers !

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