Rigol DS1074z vs DS1054z - any difference?

[don.r]

It's nothing new. I think it was ICL, who manufactured mainframes in the late '60 & '70s, whose base models had a jumper or so which could be removed which doubled the processing speed; for a price of course.

Nothing new...  Amdahl had a switch on some of their 470 mainframes that enabled increased throughput.  This allowed the customer to decide when to accept the high rent for higher throughput.  Pay for performance.

https://en.wikipedia.org/wiki/Amdahl_Corporation

IBM did this long before with their mechanical tabulating machines. They would mechanically retard the cheaper machine with a relay. When it was upgrade time, they flipped a switch and - bingo - faster machine. They also played games with pulleys and belts to achieve a similar effect.

[glarsson]

IBM did this long before with their mechanical tabulating machines. They would mechanically retard the cheaper machine with a relay. When it was upgrade time, they flipped a switch and - bingo - faster machine. They also played games with pulleys and belts to achieve a similar effect.

But this made perfect sense. You rented the machines from IBM and running at higher speed resulted in more wear and tear, i.e. higher maintenance costs for IBM. Later IBM did the same with rented printers.

Later some mainframes had a knob allowing the customer to adjust the speed themselves. Want end of month sales reports quicker? Turn up the speed and pay some extra. For the rest of the week turn down speed and save.

[michaelf]

Is there anything from Rigol about this? They just let it slide for sales reasons?

[vk6zgo]

I found the video on Youtube.  The Rigol test starts at 16:26.  If I saw that transient response, I would consider the oscilloscope broken or in need of calibration.

I remembered wrong though.  It is an actual MSO1074Z and not a hacked 1054 but that just makes the situation worse.

Please explain! (This is a very Oz " in joke", but take it literally).

I don't have a MS 1074Z, or a source of fast rise time signals, so can't reproduce the result, but the rise time looks reasonable to me, just "counting squares" on the pix, & the bit of pre ringing & overshoot aren't all that dire.

It is always difficult to know what the Rigol screen should look like, not having one---is the reading at "D"of 0.00000000ps the sticking point? 

[David Hess]

I found the video on Youtube.  The Rigol test starts at 16:26.  If I saw that transient response, I would consider the oscilloscope broken or in need of calibration.

I remembered wrong though.  It is an actual MSO1074Z and not a hacked 1054 but that just makes the situation worse.

I don't have a MS 1074Z, or a source of fast rise time signals, so can't reproduce the result, but the rise time looks reasonable to me, just "counting squares" on the pix, & the bit of pre ringing & overshoot aren't all that dire.

The problem is not the rise time although various users have reported a wide range of rise times at different signal levels which is consistent with the problem shown.  The rise time should be invariant with signal level.

The preshoot is normal for a DSO where sin(x)/x reconstruction is being used and aliasing is present.  You just have to live with it if the sample rate is insufficient for the bandwidth.  If this test was done with more channels active lowering the sample rate to 500 MS/s or 250 MS/s, then the preshoot would be worse.

The problem is that straight slope after the rising edge.  It indicates that the vertical amplifier chain is recovering from a signal which exceeded its full power bandwidth which should not be possible.

It would be instructive to test using rising and falling edges to see if that distortion is symmetrical.

I wonder if the 70 and 50 MHz models display the same behavior.

[MrW0lf]

https://www.eevblog.com/forum/testgear/rigol-ds1054z-bandwidth/msg1095201/#msg1095201
"I used 20%/80% as the step response is not OK of the rigol below 500mV/div. This means it does not have a Gaussian or flat frequency response in the 200mV range and below."

[David Hess]

https://www.eevblog.com/forum/testgear/rigol-ds1054z-bandwidth/msg1095201/#msg1095201
"I used 20%/80% as the step response is not OK of the rigol below 500mV/div. This means it does not have a Gaussian or flat frequency response in the 200mV range and below."

Is there an explanation for why this would be?  If there is a change in frequency response, it is usually for the bandwidth to be lowered at the highest gain settings while preserving a the same Gaussian response.  Having a flat instead of Gaussian frequency response on a 100 MHz oscilloscope isn't very reassuring.

It is difficult to evaluate the transient response measurements in that discussion thread without knowing more about the pulse generator(s).  Almost all normal pulse generators are not suited for this measurement.  For instance I would not use a 250 MHz PG502 with is similar in performance to the 250 MHz E-H 122 for it unless I had first evaluated it using a sampling oscilloscope or a trusted high bandwidth oscilloscope.

[Fungus]

It is difficult to evaluate the transient response measurements in that discussion thread without knowing more about the pulse generator(s).

And the cables, the connectors, etc.

[David Hess]

It is difficult to evaluate the transient response measurements in that discussion thread without knowing more about the pulse generator(s).

And the cables, the connectors, etc.

That is true at higher bandwidths but unless something is broken, nothing except the pulse is critical at 100 MHz.

One of the things he did not do in the video I linked was use the feedthrough termination on a different oscilloscope.  But the type of distortion shown is not something I would expect from a bad feedthrough termination.

Which brings up a different question; how can a feedthrough termination be objectively tested?  The fastest vertical inputs are 50 ohms so they cannot be used, or can they?  What about with a VNA?  The best option I have thought of is to use a high impedance sampling oscilloscope but they are even rarer than 50 ohm sampling oscilloscopes.