Re: Which oscilloscope to go for?

On Sat, 07 Mar 2009 17:14:24 -0500, Spehro Pefhany <speffSNIP@xxxxxxxxxxxxxxxxxxxxxxx> wrote:

On Sat, 07 Mar 2009 12:46:47 +0000, the renowned John Devereux
<john@xxxxxxxxxxxxxx> wrote:

"faiyaz" <faiyaz.pw@xxxxxxxxx> writes:

Dear all,

I am working on a hardware which has AT91SAM7S64, which works on 18.432
MHz main clock. This is the maximum frequency which can be seen on
hardware. Now we are planning to buy an analog oscilloscope, we have seen
several 30 MHz , 60 MHz and 100 MHz oscilloscopes. The 100 MHZ scope has
the least rise time - 3.6 nS, for 60 MHz it is 5-6 nS, 30 MHz has around
11 nS. Can you suggest what bandwidth we should go for?

Analog scopes are great, but for debugging microcontroller hardware a
digital scope is generally more useful (if you have to choose). For
example, a digital scope is superior for debugging:

- power on/off & reset sequencing
- code timing, latencies etc (by toggling an I/O)
- I2C, SPI, UART, ADC interfaces
- RS485, tranceiver direction switching etc

Having said that, there are some cheap logic analyser pods that may
perhaps be used for some of these instead, I am not that familiar with
them.

To address your actual question, it is indeed the risetime that you
should be looking at rather than the absolute frequency. If possible
you should get a scope that can measure the fastest rise/fall time in
your system. So that you can look at things like ground bounce,
switching glitches, reflection and crosstalk issues. Switching can be
very fast on modern processors, even if the external clock is not.

Sorry I do not have specific information on the SAM7S64. I do know
that for an analog scope I would rather buy a 400MHz unit off ebay
than a new 100MHz one for the same price. For digital there are some
new decent-looking low cost ones around now. Although I think to
compete with all features of a good analog scope too, a digitial one
would still need to be a high-end model.

Also if there is anybody who is from India and if used Scientific or Aplab
Oscilloscopes? If yes than can you evaluate and compare them?

There is an irritating trend to charge additional fees for digital
'scopes to enable firmare for the I2C, SPI, RS-232 etc.


Best regards,
Spehro Pefhany
.

Relevant Pages

  • Re: Which oscilloscope to go for?
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