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new killer scope in town - a true game changer from R&S - RTB2002 & RTB2004

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Robaroni:

--- Quote from: Hydron on December 11, 2023, 03:39:17 am ---The front board has it's own firmware - I'd be very confident that the IC reading the inputs is on that board not another.

--- End quote ---

Thanks, that helps, it was my suspicion. I may put it under a microscope and see where the encoder lead comes out.

Lino22:

--- Quote from: PeDre on December 30, 2021, 06:45:00 pm ---In the manual there is a note about the divider factor of the probe with AC coupling. Why should the voltage be different than with DC coupling? Is there an explanation for this?

Peter

User Manual v11 - Page 50

4.1 Connecting probes and displaying a signal
...
No attenuation of passive probes with AC coupling:

If AC coupling is set, the attenuation of passive probes has no effect, and voltage is applied to the instrument with factor 1:1. Observe the voltage limits, otherwise you can damage the instrument.


Edit:
Maybe the coupling capacitor is directly at the socket, even before the 1 megohm input resistor?

--- End quote ---

I am sorry for being back to this. I just want to make sure i understand.

>> I have a probe with only a 10M resistor in series, no divider. When i use it to connect a signal with both AC and DC element to RTB2000, then:

1. AC coupling
The DC part will be "stopped" by the input capacitor, and the AC part will be attenuated  10:1.
If the DC is massive, it can burn the input as it will be transferred across the probe with no attenuation.

2. DC coupling
There is no capacitor on the input, and so both AC and DC will be attenuated 10:1 at the input.

>> Now, i have a P6015A probe that has its own internal 1000:1 divider , and parasite capacity 1pF across the 1000M series resistor in it and 2pF on the input to the ground.
I measure 25kV /1us body/1ms cycle pulses from a magnetron pulser, and the probe is inserted between the pulser and the magnetron (right on the cathode) and connected to RTB2000.
There seems to be a difference between AC and DC coupling, as the DC coupling seems to load the pulser more and makes it drop out.
Do you guys have any idea why?


egonotto:
Hello,

with a divider probe you must use DC-coupling.

Since a coupling capacitor has an extremely high impedance at DC, practically the entire input voltage at the coupling capacitor drops at DC. This can be very unhealthy.

See the circuit in the picture Divider.png.

Best regards
egonotto

Lino22:

--- Quote from: egonotto on December 15, 2023, 03:37:07 pm ---Hello,

with a divider probe you must use DC-coupling.

Since a coupling capacitor has an extremely high impedance at DC, practically the entire input voltage at the coupling capacitor drops at DC. This can be very unhealthy.

See the circuit in the picture Divider.png.

Best regards
egonotto

--- End quote ---

I am afraid that it is more like this. So the input impedance the signal right after the probe can see is largely set by the 100k resistor.

EEVblog:

--- Quote from: pdenisowski on December 10, 2023, 12:19:28 am ---
--- Quote from: Robaroni on December 09, 2023, 12:14:18 pm ---Unfortunately I can't find out because your tech dept. doesn't even have basic schematics that trouble shoot down to board level. It's always been that way? Maybe you shouldn't have told me that, I think end users should have the right to repair with schematics and access to parts, it's not a good omen that your tech dept. doesn't even have schematics.

--- End quote ---

Just curious:  have you tried getting schematics for current products from Rigol or other T&M instrument manufacturers?  I would be very interested in seeing them.

--- End quote ---

So would I. I don't know of any scope manufacturer who has released schematics in probably the last 25 years.
Siglent for example do service manuals, which is fantastic, but there are no schematics:
https://siglentna.com/download/6149/?tmstv=1702895353

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