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Bandwidth check of my oscilloscope with simple means ?

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Frank_MV:
Hello,
I would like to check the bandwidth of my oscilloscope (RTB2000- 100MHz), the amplitude level at -3dB.
Unfortunately, I do not have a sine wave generator with constant amplitude.
There is only a simple signal generator available 100KHz - 150MHz - whose amplitude is unfortunately frequency dependent.
Is there a possibility with simple means ?

br,
Frank

Kibabalu:
you need a rectangular pulse with a slew rate as fast as possible. Then you measure the rise time T_r (time from 10% to 90% of the magnitude). The formula BW = 0.35/T_r gives you the bandwidth your oscilloscope at least has. If the slew rate of your pulse was not fast enough to exceed the bandwidth of your scope, than the real bandwidth could be even higher.

tggzzz:
Why do you want it measure the bandwidth of a scope? For a scope the important thing is to preserve the fidelity of the wave shape.

The best way to verify that is to examine the rise time of a step function (not an impulse). A clean transition and flat top is important, unless you know the actual waveform and are prepared to do the deconvolution yourself.

A 100MHz scope will probably have a rise time of 3.5ns, so a waveform with a rise time of less that, say, 1ns will give you a good idea of the scope's response.

Of course you can never measure a waveform with a scope, only with a scope plus probes. There are many pitfalls for the unwary associated with poor probing technique.

2N3055:

--- Quote from: Frank_MV on December 10, 2020, 07:53:50 pm ---Hello,
I would like to check the bandwidth of my oscilloscope (RTB2000- 100MHz), the amplitude level at -3dB.
Unfortunately, I do not have a sine wave generator with constant amplitude.
There is only a simple signal generator available 100KHz - 150MHz - whose amplitude is unfortunately frequency dependent.
Is there a possibility with simple means ?

br,
Frank

--- End quote ---

As for simple check, no simple answer. You need leveled signal generator (or at least one that you know has decent amplitude accuracy) and sweep.

My best advice is to go to  tggzzz's  web site in his signature and have a read.. He has lots of great info on scope use, probes and such. Quite a lot actually, so it will keep you busy for a time..

Fungus:

--- Quote from: Frank_MV on December 10, 2020, 07:53:50 pm ---Hello,
I would like to check the bandwidth of my oscilloscope (RTB2000- 100MHz), the amplitude level at -3dB.
Unfortunately, I do not have a sine wave generator with constant amplitude.
There is only a simple signal generator available 100KHz - 150MHz - whose amplitude is unfortunately frequency dependent.
Is there a possibility with simple means ?

--- End quote ---

Yes. Turn on the "Rise time" measurement on your 'scope, set it to single trigger mode and touch the probe to a 5V supply to get a fast rising edge.

For 100MhZ the rise time displayed should be around 3.5ns.

(or 3V supply, or... battery, or...some low voltage supply)

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