Rigol DS1054Z noise.

[Wisnaeme]

However, my earlier comment about the 500 uV/div vertical setting (or 5mV/div with 10x probe setting) still holds.
[/quote]
I did take the updates back to DSER and not DSFR after resetting the licenses. This made no change to the noise and didn't seem to change anything other than the maximum sensitivity. I don't think I'll be going near those signal levels so nothing lost with this.

[vk6zgo]

Maybe the Engineer who designed this feature was a digital person & regarded the analog circuitry as a sort of "pipeline" feeding the signal to the ADC.
Or perhaps he was the "bunny" who had to come up with a "quick fix" after the analog guys forget to provide a proper
ground switch.

Does that mean that the inputs of the Rigol scope can be made "floating" given that the analog guys forgot to provide a proper ground switch? Or did I misunderstand? What part is not properly grounded? The analog input of the ADC, or the digital output of the ADC?

No!
One side of the input is always earthed.

The "earthing" switch referred to shorts the non-earthed side of the input to the earthed side.
This is commonly used to establish "zero volts" to set the zero line of the display to whatever graticule line is required.

Not having such a switch is no major drama,as a BNC connector with a very short connection between "inner & outer" can be made up,which will provide a real shorted inout.

[pascal_sweden]

The "earthing" switch referred to shorts the non-earthed side of the input to the earthed side.
This is commonly used to establish "zero volts" to set the zero line of the display to whatever graticule line is required.

Isn't this only relevant for analog oscilloscopes?

[timb]

The "earthing" switch referred to shorts the non-earthed side of the input to the earthed side.
This is commonly used to establish "zero volts" to set the zero line of the display to whatever graticule line is required.

Isn't this only relevant for analog oscilloscopes?

Why would it be? I regularly move the trace to different parts of the graticule on my DSO. (Though, instead of actually switching the input to ground, they could just artificially display a zero volt trace. No real difference there.)

The only reason you wouldn't need to set the trace to GND reference is if your DSO allows you to precisely place it. On my Tek, I can set a trace to, say, 4V (the center of the graticule being 0V, the first grid line above would be 1V/nVDiv, the first grid line below center being -1V/nVDiv, etc.) but I rarely do that, as it requires going through some menus, versus twirling a knob.

[ebastler]

The "earthing" switch referred to shorts the non-earthed side of the input to the earthed side.
This is commonly used to establish "zero volts" to set the zero line of the display to whatever graticule line is required.

Isn't this only relevant for analog oscilloscopes?

Why would it be? I regularly move the trace to different parts of the graticule on my DSO.

I do that too. But my DSO (as, I believe, the vast majority of digital scopes) has channel indicators on the side of the screen, which show where the 0V level is. So I agree with pascal_sweden that switching the input to GND mode to get your bearings is a bit redundant with DSOs. (While in analog scopes it was the only quick way to establish where 0V are.)

[tautech]

The "earthing" switch referred to shorts the non-earthed side of the input to the earthed side.
This is commonly used to establish "zero volts" to set the zero line of the display to whatever graticule line is required.

Isn't this only relevant for analog oscilloscopes?

Why would it be? I regularly move the trace to different parts of the graticule on my DSO.

I do that too. But my DSO (as, I believe, the vast majority of digital scopes) has channel indicators on the side of the screen, which show where the 0V level is. So I agree with pascal_sweden that switching the input to GND mode to get your bearings is a bit redundant with DSOs. (While in analog scopes it was the only quick way to establish where 0V are.)

For those that don't want the display cluttered with on-screen measurements the need for grounding the input is necessary when setting the waveform zero level exactly to a graticule so that waveform amplitudes can be quickly observed.....a methodology for many that is a carry over from the days of no OSD on CRO's.

Not all use set methods of scope use and manufacturers know this.

[ebastler]

... my DSO (as, I believe, the vast majority of digital scopes) has channel indicators on the side of the screen, which show where the 0V level is. So I agree with pascal_sweden that switching the input to GND mode to get your bearings is a bit redundant with DSOs. (While in analog scopes it was the only quick way to establish where 0V are.)

For those that don't want the display cluttered with on-screen measurements the need for grounding the input is necessary when setting the waveform zero level exactly to a graticule so that waveform amplitudes can be quickly observed.....a methodology for many that is a carry over from the days of no OSD on CRO's.

Not all use set methods of scope use and manufacturers know this.

I was not talking about measurements, but about the channel indicators in the left margin of the screen (circled in the attached screenshot). These do the job for me: I can see, at any time and without the need for a GND switch, where the 0V level is, and can align it to a graticule  line if needed.

[alsetalokin4017]

Many owners of the DS1054z will have noticed that the displayed "zero volts baseline" rarely lines up exactly with the channel baseline indicators, and in some cases can be way off.

This is an uncorrectable DC offset and should be factored into any interpretation of Measurements that reference the channel baseline values. It also can move around, depending on whether you have run the self-cal routine at your present lab ambient temperature.



 

[tautech]

Many owners of the DS1054z will have noticed that the displayed "zero volts baseline" rarely lines up exactly with the channel baseline indicators, and in some cases can be way off.

This is an uncorrectable DC offset and should be factored into any interpretation of Measurements that reference the channel baseline values. It also can move around, depending on whether you have run the self-cal routine at your present lab ambient temperature.

Not at all uncommon for DSO's but not the end of the world either.
Self Cal after an appropriate warm up time should get any zero offset down below a mV, then if this amount matters you are really using the wrong tool for the job.

[ebastler]

Many owners of the DS1054z will have noticed that the displayed "zero volts baseline" rarely lines up exactly with the channel baseline indicators, and in some cases can be way off.

This is an uncorrectable DC offset and should be factored into any interpretation of Measurements that reference the channel baseline values. It also can move around, depending on whether you have run the self-cal routine at your present lab ambient temperature.

Not at all uncommon for DSO's but not the end of the world either.
Self Cal after an appropriate warm up time should get any zero offset down below a mV, then if this amount matters you are really using the wrong tool for the job.

Thanks, tautech. And the offset values alesatonkin's scope is showing are indeed all around 0.25 mV (assuming that all channels were set for 10x probes, as indicated in the screenshot for channel 4). Nothing to worry about, I would say.

[tautech]

Many owners of the DS1054z will have noticed that the displayed "zero volts baseline" rarely lines up exactly with the channel baseline indicators, and in some cases can be way off.

This is an uncorrectable DC offset and should be factored into any interpretation of Measurements that reference the channel baseline values. It also can move around, depending on whether you have run the self-cal routine at your present lab ambient temperature.

Not at all uncommon for DSO's but not the end of the world either.
Self Cal after an appropriate warm up time should get any zero offset down below a mV, then if this amount matters you are really using the wrong tool for the job.

Thanks, tautech. And the offset values alesatonkin's scope is showing are indeed all around 0.25 mV (assuming that all channels were set for 10x probes, as indicated in the screenshot for channel 4). Nothing to worry about, I would say.

Some might insist the display and onscreen measurements align at zero volts when directed to in the UI but then how is this being accomplished.......with a hard zero SW command? Then will subsequent measurements be correct after ignoring any internal noise in a DSO?
Let's post some screen shots with differing acquisition and detection settings to see if the zero level becomes better aligned.

[David Hess]

You must admit it is an elegant solution,if you don't anticipate the above "bugs".

Maybe the Engineer who designed this feature was a digital person & regarded the analog circuitry as a sort of "pipeline" feeding the signal to the ADC.

Or perhaps he was the "bunny" who had to come up with a "quick fix" after the analog guys forget to provide a proper ground switch.

Or marketing wanted the appearance of lower noise.  Doesn't the Rigol 2000A series do this as well?

It may be a safety issue for the oscilloscope.  In a proper design, ground coupling may be used to precharge the AC coupling capacitor preventing damage to the input circuits.

[Fungus]

Thanks, tautech. And the offset values alesatonkin's scope is showing are indeed all around 0.25 mV

??

More like a couple of mV. He has his 'scope set to 20mV/div.

According to the manual:

DC Offset Accuracy: ±0.1 div ±2 mV ±1% offset value

I'd say it's in spec.

Here's mine FWIW

[David Hess]

If you ground the DC coupled input externally, then you can see if the input bias current through the 1 megohm input shunt is causing any offset.

It seems odd that all of the offsets are in the same direction with about the same magnitude but as pointed out, without an physical analog ground coupling function, the automatic calibration may not be able to remove it.

[ebastler]

Thanks, tautech. And the offset values alesatonkin's scope is showing are indeed all around 0.25 mV

??
More like a couple of mV. He has his 'scope set to 20mV/div.

He has the scope configured for 10x probes. So that's 20mV/div at the (presumed) probe tip, but 2mV/div at the scope's BNC input. Hence, the offset at the actual scope input is well below a mV, right?

[Fungus]

He has the scope configured for 10x probes. So that's 20mV/div at the (presumed) probe tip, but 2mV/div at the scope's BNC input. Hence, the offset at the actual scope input is well below a mV, right?

Oh, I see what you mean.... yes, electrically it's 10x less.

[vk6zgo]

The "earthing" switch referred to shorts the non-earthed side of the input to the earthed side.
This is commonly used to establish "zero volts" to set the zero line of the display to whatever graticule line is required.

Isn't this only relevant for analog oscilloscopes?

An earthing switch of this nature is trivial to provide in analog 'scopes----just provide another position on the "input coupling" switch.
It gets messier with DSOs ,where the switch is normally a relay,driven ultimately by software.

As I said before,if there isn't an actual earthing switch,a  real "hard" earth can be provided by a shorted BNC connector.

If you put a real short across a DSO input,& your display says something other than zero volts ( in other words,an offset),you can see if the 'scope can auto calibrate that out,or just take a note of the offset for later reference.

The use of such is an example of a technique which seems to have been lost in this era of higher stability in test equipment,that of presenting the equipment with a known condition.

People do seem to assume that the accuracy of their equipment is good,& if all goes well that is OK,but in unforseen circumstances,it is good to know whether the DUT has a problem,or your test equipment is lying to you,

[Keysight DanielBogdanoff]

On closer investigation the "I unplugged everything" was proven correct, however there was a USB powerbank device that was switched on and remained so even with power removed from everything else. I sniffed it out using a long power cable and walking the property with the scope.

I'm imagining this (for better or for worse. Probably for worse.)

[nctnico]

You forgot to measure the noise from the brain of that grey haired dude you pushed away