Oscilloscope Memory Depth

[echen1024]

Hi all,

I am looking for a good scope for my general electrical tinkering, which mainly involves digital electronics communicating over I2C, UART, and SPI. Recently, I have been in need of an oscilloscope. Do you think a Tek TDS1002B or TDS220 with a 2.5k memory depth will be enough to capture the whole of the transmission? I am mainly looking at Tek scopes, since I almost have an attachment to them, due to my 465 as my 9th birthday gift that started my interest in electronics, but brands such as Rigol, Atten, and HP will do. Please recommend me a few models, and my budget is not to go over $500. 

Thanks.

[Hydrawerk]

Do you think a Tek TDS1002B or TDS220 with a 2.5k memory depth will be enough to capture the whole of the transmission?

2.5kbytes is too small memory. Well, Tektronix was the first digital scope I ever saw, i liked it. But nowadays Tektronix makes no scopes that are bang per buck. With 500USD i would buy a Rigol or Siglent... Or collect more money and choose Rigol DS2000 series or maybe Agilent DSOX2000 series...

[echen1024]

Ok. Thank you. I will probably just buy the lowest priced Rigol DS1052E and hack it up to the 100MHz standard.

Thanks

[mike1305]

Best way to determine the amount of memory you need is to work backwards.

Let's say you're measuring a 100kHz SPI bus. You'll need to be sampling around 400,000 Samples/sec (4x bandwidth is a fine approximation). Then ask yourself how much time you need to capture. If you need 4ms to capture your longest SPI transaction, then you'll need at least 1,600 points of memory.

[memory] = [sample rate] x [capture time]

mike