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New Rigol DS7000
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mindy:
Hello,

So far I'm happy with MSO7k performance & functionality, but I'm a bit concerned of my device calibration and wondering is this something what can be fixed by a Firmware upgrade or I should be filling a warranty card for my brand new scope :(
I'm unable to get a perfectly flat 1k square with included passive probes RP3500A, I'm getting a small dip at the beginning of each wave.
Can this be a source of a small overshoot observed on a signal generator?

When I tried a DIY 1k probe on a 50 \$\Omega\$ input with 1:20 attenuation I got a perfectly flat square wave.
Does anyone have a similar experience or can suggest if it's still in a acceptable error margin or should I be concerned and send it for a repair?
BTW tried to re-calibrate multiple times but this does not helped
Fungus:

--- Quote from: mindy on February 10, 2019, 12:34:34 pm ---I'm unable to get a perfectly flat 1k square

--- End quote ---

I'd say that was due to the probing technique, nothing to do with the 'scope.


--- Quote from: mindy on February 10, 2019, 12:34:34 pm ---Can this be a source of a small overshoot observed on a signal generator?

--- End quote ---

What does a piece of 50 Ohm terminated coax cable give you?


--- Quote from: mindy on February 10, 2019, 12:34:34 pm ---should I be concerned and send it for a repair?

--- End quote ---

No.
mindy:

--- Quote from: Fungus on February 10, 2019, 11:15:40 pm ---
--- Quote from: mindy on February 10, 2019, 12:34:34 pm ---I'm unable to get a perfectly flat 1k square

--- End quote ---

I'd say that was due to the probing technique, nothing to do with the 'scope.

--- End quote ---

I've tried to use a spring for my probe ground to minimise signal ringing on measuring signal from my integrated AWG what made little to none effect.
I saw very similar result (overshoot) on a different (external) signal source as well.
But the most important is a compensation 1k square wave which clearly shows a dip and can not be fully compensated.
This should eliminate an inductive loading from the equation as compensation signal ground is connected internally.
Obviously I'm not going to solder my probe tip to compensation clip for a better contact, but I did my best to make sure that it has a good contact.
Any further tips to try before concluding that either Probe OR Scope is defective?


--- Quote from: Fungus on February 10, 2019, 11:15:40 pm ---
--- Quote from: mindy on February 10, 2019, 12:34:34 pm ---Can this be a source of a small overshoot observed on a signal generator?

--- End quote ---

What does a piece of 50 Ohm terminated coax cable give you?

--- End quote ---

As I mentioned I tried a quick test (1k 0.25W resistor directly connected to compensation signal & Channel 1) and I got a perfectly flat square wave. Then I'll have more time I'll make a bit more robust probe with compensation and parasitics taking into account. Differential probe would do even better. But my concern right now is about 1M ohm range / included Probes quality.
nctnico:
You can try a coax cable and a 50 Ohm feed-through terminator. A 1M input usually has various frequency cross-over points which need to be adjusted. Perhaps you are seeing the crossover between the LF and HF path of the 1M input. The 50 Ohm input path may be entirely different.
KlausF:
Nice device, but imho way too expensive, regrettably.
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