HELP me with buying a Digital Oscilloscope. Bandwidth selection

Hello..!!

I would like to buy an oscilloscope to work with power management and with microcontrollers.

I have read many articles, all says that you should have an oscilloscope with bandwidth five times more than the frequency you want to measure.

Please suggest me with an oscilloscope bandwith which one to go for.? I thought of getting an 100Mhz .

Following that rule then that would allow you to see 20MHz signals and given the arduino is a 16MHz processor then that is fine. But just like money you can never have too much bandwidth, however 100MHz is a good choice. I have used a 20MHz analogue scope for the best part of 40 years and it has served me well.

Don't forget with digital oscilloscopes sampling rate is just as important as bandwidth. Technically, to see a waveform properly in one go you need a sampling rate 10x higher than the bandwidth. So a 100Mhz scope needs 1GSa/sec, now you can get by with less if the waveform is repetitive, because the scope can interpolate samples to fill in the details, but if you are are trying to trace glitchy behavior you need the higher sample rate.

PedroDaGr8: Don't forget with digital oscilloscopes sampling rate is just as important as bandwidth. Technically, to see a waveform properly in one go you need a sampling rate 10x higher than the bandwidth. So a 100Mhz scope needs 1GSa/sec, now you can get by with less if the waveform is repetitive, because the scope can interpolate samples to fill in the details, but if you are are trying to trace glitchy behavior you need the higher sample rate.

I am looking forward to buy this Oscilloscope here http://www.metravi.com/prod_detail.php?prod=DSO-5100A here is the datasheet of it http://www.metravi.com/PDF/DSO%20Catalogue.pdf

That would work great. However, Arduino's are basically operating in the digital world, with everything operating from the 16 MHz clock. A good logic analyzer/protocol analzer like the saleae 8 or 16 (channel) will turn out to be much more useful, especially when reviewing serial data (SPI, Serial, I2C) or making time measurements. http://www.saleae.com/logic http://www.saleae.com/logic16 Anytime you are dealing with "glitchy" signals or behavior it will often turn out to be lack of power supply decoupling capacitors.

CrossRoads: That would work great. However, Arduino's are basically operating in the digital world, with everything operating from the 16 MHz clock. A good logic analyzer/protocol analzer like the saleae 8 or 16 (channel) will turn out to be much more useful, especially when reviewing serial data (SPI, Serial, I2C) or making time measurements. http://www.saleae.com/logic http://www.saleae.com/logic16 Anytime you are dealing with "glitchy" signals or behavior it will often turn out to be lack of power supply decoupling capacitors.

CrossRoads makes a good point, for arduino or other digital communications devices an oscilliscope is not the most ideal device. A logic analyzer would be more helpful. The difference is that a logic analyzer is great for monitoring timing between signals (it only measures if lines are high or low, it doesn't measure if their exact voltage.

Also, with arduino yeah most glitchy behavior is going to be power supply decoupling related. If you are doing other electronics work such as SMPS or what not an oscilloscope becomes MUCH more useful.

If you are working with measurement or analog circuits, a scope will be useful. I have the Rigol DS1052e. For around $325, it is 50 mhz/ 1 GSS. I hacked it to do 100 mhz. There is also a hack to turn it into a spectrum analyzer.

An oscilloscope is a capex so I would target min 200MHz BW today, as well as Logic Sniffer LA (16channels, 200MHz, $50).. ;)

I mostly work with microcontrollers and timers..

My main need for buying an oscilloscope is for decoupling the power supply ripples due to switching voltage regulators or other reasons, to measure output timing and voltage of of timers and microcontrollers and etc. I may also use it in detecting RF & EMI interferences ..

If this is your first 'scope, and given the uses for it you mention, my advice is to get a decent analog unit on ebay. I have an inexpensive DSO and an old Tektronix analog and I use the Tek far more than the DSO. The reason? Mainly because the persistence of the analog scope allows me to see the spikes and glitches in much better detail. DSOs with persistence are coming down in price but you’re looking at about 7-800$. You can find a good analog scope, e.g., Hameg or Tektronix 2-ch 50-60MHz for less than 100$ and you’ll learn a lot about how scopes work.
And you can add the Saleae logic analyzer mentioned above and still come out spending less than a cheap, entry-level DSO.
My two cents, anyway.

CrossRoads: A good logic analyzer/protocol analzer like the saleae 8 or 16 (channel) will turn out to be much more useful, especially when reviewing serial data (SPI, Serial, I2C) or making time measurements. http://www.saleae.com/logic http://www.saleae.com/logic16

At the risk of taking the topic off at a slight tangent; I've seen one or two positive posts for these analysers on this forum. Having done a little looking around, they appears to be available here in the UK, along with a similar Logic Analyzer and Signal Generator sold by IKALogic.

The latter item doesn't seem to be as well specced, but comes in at less than half the cost of the 8 channel saleae. Does anyone have any experience, or opinions, as far as comparing the two offerings is concerned?

pete, At the risk of keeping this off-topic, a quick follow-up. There is a review of the Saleae 8-channel unit here: http://www.eevblog.com/2013/03/09/eevblog-436-saleae-usb-logic-analyser-review-teardown/

I have an inexpensive DSO and an old Tektronix analog and I use the Tek far more than the DSO. The reason? Mainly because the persistence of the analog scope allows me to see the spikes and glitches in much better detail. DSOs with persistence are coming down in price but you're looking at about 7-800$. You can find a good analog scope, e.g., Hameg or Tektronix 2-ch 50-60MHz for less than 100$ and you'll learn a lot about how scopes work.

This ^^^. I 100% agree.

The "cheap" digital chinese scopes out there (Owon, Rigol etc.) can't match the speed/performance of an even old analog scope in this aspect.

Since this item was originally posted, major oscilloscope manufacturers have started offering more affordable digital oscilloscopes with features that earlier models did not have. So, instead of using a separate logic analyzer, you can now purchase a relatively inexpensive scope with logic analysis capabilities. Some can be outfitted with an eight-channel logic analyzer and serial protocol analyzer. This lets you make all the measurements you need when designing and debugging a microcontroller system with a single instrument.

The rule about choosing a scope with a bandwidth that's five times as high as the highest frequency signal that you'll be measuring really only applies if you're going to be making measurements such as rise and fall times on square wave signals. The reason for this is that square wave signals have frequency components at odd harmonics to the fundamental frequency. Without enough bandwidth, a scope will attenuate these harmonics and distort the signal. For developing and debugging Arduino-base microcontroller systems, 100 MHz should be sufficient bandwidth.

My vote is for 'scope over logic analyzer any day - unless you have parallel busses to deal with a 'scope is much more capable and will catch all the faults a logic analyzer misses (signal reflection, hi-Z floating signals, heavy ringing, wrong voltages, noise spikes, etc etc etc)

Can any logic analyzer debug even a 12V level shifter?