200mhz oscillorscope probe question

[Gazmon]

Hi,

If i have a 200mhz scope with a 100mhz probe attached and measure a 555 timer circuit connected to an flashing LED for example, then i attach a 200mhz probe to measure the same circuit

will i see a difference in readings using the higher rated scope probe.

basice question but still learning

thansk

Gazmon

[tggzzz]

Hi,

If i have a 200mhz scope with a 100mhz probe attached and measure a 555 timer circuit connected to an flashing LED for example, then i attach a 200mhz probe to measure the same circuit

will i see a difference in readings using the higher rated scope probe.

basice question but still learning

thansk

Gazmon

Good to see someone thinking before doing. The former gives you a better chance of doing the latter correctly. The latter confirms/denies your understanding of the former. Both are necessary.

First rule of thumb: risetime = 0.35/bandwidth.
Second rule of thumb: risetimes add as sqrt(t1*t1+t2*t2).

Different scope probes and scopes use slightly different definitions of bandwidth, but in your case the differences will be moot. Just plug in the 100MHz and 200MHz, and compare to the 555's waveforms.

For more information about probe types, measurements, and safety, have a look at the references at https://entertaininghacks.wordpress.com/library-2/scope-probe-reference-material/

[TK]

I don't think you will see any difference with a standard 555 (LM555, NE555) as rise time is 100ns.  It can make a difference when using LMC555 (rise time of 15ns).

[ebastler]

As TK and tggzz have said -- a regular 555 is far slower than 100 MHz, hence you will not observe any difference. But for signals which are approaching the bandwidth limit fo your scope and probes, the amplitude drops caused by the scope and the probes, respectively, will add up.

While you are learning, keep an eye on the unit designations and make it a habit to capitalize them correctly. The "m" prefix stands for milli = 1/1000. The "M" prefix stands for Mega = 1 000 000. And the unit for frequency, Hertz = 1/s, is abbreviated as "Hz" with a capital H. While spelling Hz as "hz" is merely irritating, mixing up "m" and "M" is really messing up your numbers.

[Gazmon]

Thanks for the reply’s


Ok so how can I check my 200mhz oscilloscope and 200mhz probe are what they say , with limited kit

I have a 24 MHz sigen, I’m into op amps etc

I’m guessing I can’t set up an experiment very easily without a better kit yes?

[TK]

What brand and model is your oscilloscope?

[TK]

You need to get a fast edge pulse generator

[tggzzz]

Ok so how can I check my 200mhz oscilloscope and 200mhz probe are what they say , with limited kit

I have a 24 MHz sigen, I’m into op amps etc

Obvious question: if the equipment is usefully faster than your circuit, why do you need to verify the equipment's performance. (Don't look at the TEA thread .

Opamps won't help, and a 24MHz siggen is likely to have well controlled edges that will be too slow to be useful.

For digital signals, remember to concentrate on the risetime - the fundamental frequency (e.g. 24MHz) is completely irrelevant, e.g. see https://entertaininghacks.wordpress.com/2018/05/08/digital-signal-integrity-and-bandwidth-signals-risetime-is-important-period-is-irrelevant/

[Gazmon]

I have a GW Instek 1000b 2 channel, i upgraded it to the 200mhz via the software

The scope says it’s 200 MHz , I just want to try and confirm it’s is

[ebastler]

_________________________
There are lies, damned lies, statistics - and ADC/DAC specs.
Gliding aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
Having fun doing more, with less

Off-topic, but I have meant to ask a few times when I came across your signature:
What do you mean by "span" here, and how can it be bought?

(Honest question from a non-native speaker. Thanks!)

[TK]

You have 2 options:

1) Get a fast edge pulse generator and it will push the scope input to the limits and measure the min rise time it is capable of
2) Input a 1Vpp sinewave and measure the attenuation. It should be 3dB attenuation at 200MHz and increase the attenuation as you increase the frequency.  You need a signal generator that can generate higher than 200MHz sinewave.

[james_s]

Build an avalanche pulse generator, the classic design by Jim Williams can be built using many common inexpensive transistors, to get rise times well beyond the capabilities of a 200MHz scope you don't need anything exotic.

[tggzzz]

_________________________
There are lies, damned lies, statistics - and ADC/DAC specs.
Gliding aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
Having fun doing more, with less

Off-topic, but I have meant to ask a few times when I came across your signature:
What do you mean by "span" here, and how can it be bought?

(Honest question from a non-native speaker. Thanks!)

I doubt many native speakers would understand it, at least not without thought!

Span as in wingspan. Basically longer thinner wings are better at gliding speeds - you can go further and/or faster between thermals. As you can imagine, longer and thinner tends to be more expensive.

[tggzzz]

Build an avalanche pulse generator, the classic design by Jim Williams can be built using many common inexpensive transistors, to get rise times well beyond the capabilities of a 200MHz scope you don't need anything exotic.

Pulses don't tell you much, unless you know the shape and size of the pulse, and do the deconvolution to find out the UUT's response.

The latter is tedious, especially with non-digitising scopes.

[ebastler]

Span as in wingspan. Basically longer thinner wings are better at gliding speeds - you can go further and/or faster between thermals. As you can imagine, longer and thinner tends to be more expensive.

Ahaa! Thank you!
I had totally misconstrued the "gliding" bit, although it's obvious in hindsight. Had been wondering how an aphorism can glide... 

[joeqsmith]

Hi,

If i have a 200mhz scope with a 100mhz probe attached and measure a 555 timer circuit connected to an flashing LED for example, then i attach a 200mhz probe to measure the same circuit

will i see a difference in readings using the higher rated scope probe.

basice question but still learning

thansk

Gazmon

Assuming they are both 10X, you compensate them, you don't use that 6" groundish lead that comes with probes and you attach them the same way,  then I doubt you would see much if any difference.

[tggzzz]

Span as in wingspan. Basically longer thinner wings are better at gliding speeds - you can go further and/or faster between thermals. As you can imagine, longer and thinner tends to be more expensive.

Ahaa! Thank you!
I had totally misconstrued the "gliding" bit, although it's obvious in hindsight. Had been wondering how an aphorism can glide... 

Coffee meets keyboard!

I ran into character limits in the .sig, and had to be too brief

.sig changed: s/Gliding/Glider pilot's/

[David Hess]

The edge from AC or LVC logic is fast enough to reveal the difference between 100 and 200 MHz operation.  The circuit will need to be directly connected to the probe tip without using the probe's standard ground lead which is too long for accurate results even at 100 MHz.

The bandwidth rating of an oscilloscope probe is better understood as the bandwidth within which the probe will faithfully reproduce the input.