This is stupid. You don't know what you're doing. With that setup it is perfectly normal to get -3 dB at 100 MHz. 100 MHz does not mean, that this will still be shown at 100%. And when you then take into account that the cable also has a capacitance this is exactly as spec'ed.
First of all, I do not know what you want to express! If you do not agree with my experiment, you can prove to be more effective to let everyone know. But please do not use a number of rude words.
This is definitely NOT a fault, but a simple alias problem. This DSO has one channel=1000Ms/S but two channel=500Ms/S, you can see it on the display. 500Ms/S=5 sample per sine wave, too low for good measurement. This DSO has been set to use sinx/x interpolation, because even when undersampled (only 5 samples per cycle!) the display shows a clean sine wave. Sinx/x is a stupid, dangerous feature. Linear interpolation gives warning of undersampling, triangles=undersampled.
The operator does not make it clear if the cable feeding the DSO is correctly terminated or how it's connected. At 100MHz, the cable is a transmission line and could easily form a stub if unterminated. I don't speak the language, but I also don't think this video proves anything at all.
You can't expect to read the full amplitude @100MHz on a 100MHz scope, here you can only expect to read an amplitude attenuated 3dB.
100MHz BW means that the -3dB point is at 100MHz.
So if you input 60mVpp@100MHz you should never expect to read more than 42mVpp (-3dB) on a 100MHz scope.
With a 60mVpp@100MHz input signal you measure 46mVpp, that's above the -3dB limit of 42 mVpp, so this scope seems to work just fine and well withint BW specifications.
The amplitude drops from 46mVpp to 38mVpp when you turn on both channels at the same time. I missed that the first time I saw it. Would be easier if you spoke in English.
I hope this is only a problem at the BW limit?
Or does the amplitude also drops when you turn on an extra channel at 50MHz?
This is stupid. You don't know what you're doing. With that setup it is perfectly normal to get -3 dB at 100 MHz. 100 MHz does not mean, that this will still be shown at 100%. And when you then take into account that the cable also has a capacitance this is exactly as spec'ed.
Pipolay01 1 year ago 3
First of all, I do not know what you want to express! If you do not agree with my experiment, you can prove to be more effective to let everyone know. But please do not use a number of rude words.
InstrumentVu 1 year ago
There is no any BW issue, but we can see many things here.
1. input amplifier working at it's limit, at -3db point, we can calculate with that.
Feeding in 60mVpp getting only 40-50mVpp, it's exceptable.(plus cable attenuation,termination problems, etc?)
2.When the second chanel switched on, the signal undersampled, sinX generating a "fake-sine",amplitude droops again.
3.Before end of video, in equialent time mode, undersampling issue 'gone, we can see the right (-3db) amplitude again!
mioporfeszosz 2 years ago 3
mioporfeszosz, you are absolutely right on all points!
flolic 2 years ago 3
Actually, Rigol designs and produces low end Agilent scopes.
hrvojevz 2 years ago
Comment removed
hrvojevz 2 years ago
This is definitely NOT a fault, but a simple alias problem. This DSO has one channel=1000Ms/S but two channel=500Ms/S, you can see it on the display. 500Ms/S=5 sample per sine wave, too low for good measurement. This DSO has been set to use sinx/x interpolation, because even when undersampled (only 5 samples per cycle!) the display shows a clean sine wave. Sinx/x is a stupid, dangerous feature. Linear interpolation gives warning of undersampling, triangles=undersampled.
colinbeeforth 2 years ago
The operator does not make it clear if the cable feeding the DSO is correctly terminated or how it's connected. At 100MHz, the cable is a transmission line and could easily form a stub if unterminated. I don't speak the language, but I also don't think this video proves anything at all.
colinbeeforth 2 years ago
If two DSO's are saying the same, then probably the signal generator is lying...
paliver 2 years ago
I do not think so that sg ave any problem because I' rely on this guy to eat..ho...ho.
By the way if you have a same model of the oscilloscope may be you can check it up too.
InstrumentVu 2 years ago
Why do you say the BW is out of spec?
You can't expect to read the full amplitude @100MHz on a 100MHz scope, here you can only expect to read an amplitude attenuated 3dB.
100MHz BW means that the -3dB point is at 100MHz.
So if you input 60mVpp@100MHz you should never expect to read more than 42mVpp (-3dB) on a 100MHz scope.
With a 60mVpp@100MHz input signal you measure 46mVpp, that's above the -3dB limit of 42 mVpp, so this scope seems to work just fine and well withint BW specifications.
ITubeTooInc 2 years ago
Sorry, now I see what the prblem is.
The amplitude drops from 46mVpp to 38mVpp when you turn on both channels at the same time. I missed that the first time I saw it. Would be easier if you spoke in English.
I hope this is only a problem at the BW limit?
Or does the amplitude also drops when you turn on an extra channel at 50MHz?
ITubeTooInc 2 years ago