Electronics > Beginners
Oscilloscope bandwidth - is jump from 100MHz to 200 MHz significant?
bmdaly:
Hi,
I'm a hobbyist proposing to upgrade from my 10MHz Picoscope 2204 to a Siglent SDS1104X-E, primarily for the 4 channels.
My main area of interest at the moment is analogue electronics, and I'm working my way through a series of lab tutorials in "Learning the Art of Electronics". I expect that being able to monitor multiple points on the circuits I'm building and view the signals' relative phases and amplitudes on a single screen will be a big help to learning.
I've also done a couple of microcontroller courses in the past (using TI MSP432 and TM4C123 boards), and also use Arduino boards.
I've read Performa01's in-depth review https://www.eevblog.com/forum/testgear/siglent-sds1104x-e-in-depth-review/ of the SDS1104X-E and the SDS1202X-E, including his chapter comparing the bandwidth of these devices, and have decided that the 100MHz model is sufficient for what I need - particularly given the 50% cost premium for double the bandwidth (but no corresponding increase in sampling rate), and limited (lack of???) anti-aliasing on the 200MHz model.
Before finalizing the decision, I wonder if there are any use cases where the extra bandwidth would really make a significant difference to understanding what's going on in a circuit?
I don't want to be in a position a few months down the road thinking "if only I had a little extra bandwidth...", but equally, I need to be pragmatic and draw the line somewhere.
Any comments from people who have been down this road would be appreciated.
Thanks in advance,
Brian
capt bullshot:
For your applications, you'll be fine with a 100MHz scope. My most used scope is an old and crusty 100MHz TDS220, next stop is the good old analog 7603.
4 channels is pretty useful, most of the time you'll find yourself using one or two channels.
Having more than 100MHz BW also requires more advanced probing techniques, and often 50 Ohm terminated inputs. Your vanilla 10x scope probe won't make any use of more than 100MHz BW - you'll just see more ringing. So 100MHz, or even as low as 50MHz is enough for the most tasks in debugging analog and uC circuitry.
danadak:
More important for analog work are things like high G differential preamp with
high CM rejection.
Or spectrum analyzer.
You can look at older Tek series 7000, its a mainframe that takes many different plugings.
Still very useful in today's work. Plugins like DMM, High G diff preamp, spectrum analyzers
(several), FET input plugin, curve tracer.........
http://w140.com/tekwiki/wiki/7000-series_plug-ins
Regards, Dana.
tggzzz:
It depends on what frequency analogue signals you will be using, what you will be looking for, and what logic family you will be using.
Sometimes analogue circuits can oscillate at a much higher frequency than you are expecting ("amplifiers oscillate, oscillators won't").
In some analogue applications, harmonics of the fundamental frequencies are important; factor that into your assessment.
A 100MHz scope will (just about) allow you to see a 3.5ns risetime; a 200MHz scope 1.8ns. Logic families from the early 80s (LSTTL, STTL) have that kind of risetime. Some modern jellybean logic families have sub-nanosecond risetimes (e.g. 74lvc). If using similar families, a principal use of a scope is to check "signal integrity", which needs all the bandwidth you can get.
Most "high" impedance *10 scope probes with a 6"/15cm ground lead self-oscillate at ~100MHz. A 200MHz scope will show you that, but a 100MHz scope will disguise it :) At such frequencies construction techniques and probing techniques become important.
rstofer:
The question "How much bandwidth do I need?" comes up about once a week or so. There will be threads here in the Beginners forum as well as over in the Test Equipment forum. But mostly here...
For most projects using sine waves (audio) a 100 MHz scope is probably overkill. Where 100 MHz tends to come up short is looking at square waves. A 100 MHz scope can do a decent (but far from perfect) representation of a 20 MHz square wave and that is because it can only faithfully display the 5th harmonic (and even that will be attenuated). A 200 MHz scope can similarly display a 40 MHz square wave. For Arduino projects, the clock is just 16 MHz so pin signals won't be running anywhere near that fast. Serial decoding (all 4 channels of SPI) will be quite helpful.
Move up to FPGAs and the bandwidth requirement goes way up. Probably much farther than 200 MHz.
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