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Oscilloscope specs - which are really important

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nctnico:
Who said a scope should be new? There are many excellent oscilloscopes for sale on Ebay.

Wuerstchenhund:

--- Quote from: nctnico on January 16, 2013, 12:13:18 pm ---Who said a scope should be new? There are many excellent oscilloscopes for sale on Ebay.

--- End quote ---

I fully agree. Personally I'd rather buy a good second hand scope from one of the major manufacturers than any of the cheap Rigol/Atten/Siglent/Hantek/whatever scopes from China. I had a chance to play with a few of these China scopes, and while the build quality of some of them is quite good and they come with tons of features, for me a stable firmware, a decent user interface and reliability/support are more important with a measurement device. I know I will get shot for saying this and that many are happy with their China scopes but that is my opinion.

Price is another advantage of buying used. Yes, there are lots of commercial dealers that try to flog off 15 or 20 year old scopes for more than the cost of a brand new modern counterpart (and many private sellers seem to take these insane prices as orientation) but if you can wait then there are definitely interesting deals out there.

As to what features are required, well as others said this depends on what you want to do with it. Buying features just because you have been told that this is a 'must-have' no matter what means you're wasting money. Analyze your requirements and make a list of what *you* need and buy something that has what you need and fits your budget. I'd also not put too much value into buying a scope that can be upgraded as when you finally need that new feature you may find that it's more economical to sell your scope and get one which already has the new feature.

Taking myself as an example: large sample memory isn't a concern for me at the moment. My basic scope is an old HP 54510A 250MHz 2Ch 1GSa/s DSO with 8k memory per channel, and for everything more demanding I also have a HP 54542A 500MHz 4Ch 2GSa/s DSO which has 32k memory per channel. Both scopes were cheaper than most 100MHz China scopes. Important for me was that a scope can use it's full sampling rate on all channels and not when using only two or a single channel, a limitation that is often found not only with cheaper China scopes but also with some pretty expensive scopes from well known manufacturers like LeCroy. Should the day come that I need more memory then I'll sell on one of my scope without much loss and just buy a suitable second hand scope which has the memory I need.

jabramo:
If your really interested in added decoding functionality maybe take a gander at some Tek 2000's and 3000's someone posted here on the forum some links of some guys who figured out how to reverse engineer the modules and make there own with a 0.25$ microchip eeprom.

I used a 2000 series Tek for a while, the one with 4 isolated channels and I generally wasn't a big fan. However it did work. If your big on some specific added functionality it might be worth a look

Here's the link to the information
http://forum.tsebi.com/viewtopic.php?f=4&t=113

nctnico:
AFAIK there is no need to hack because Tektronix has firmware with all options enabled available for download on their website. Be aware that the TDS2000 series scopes have a very short (2.5k points) memory. The TDS3000 series doesn't do much better with only 10k points. Serial protocol decode is pretty much useless with these short memories.

alm:

--- Quote from: nctnico on January 19, 2013, 04:18:35 pm ---AFAIK there is no need to hack because Tektronix has firmware with all options enabled available for download on their website.

--- End quote ---
Tektronix released a firmware update for the TDS 3000 series that enabled some of the options (from memory it was advanced triggering, FFT and video triggering). Other options, like advanced video features, advanced analysis, and limit/mask testing still required an expensive plugin EEPROM module.


--- Quote from: nctnico on January 19, 2013, 04:18:35 pm --- Be aware that the TDS2000 series scopes have a very short (2.5k points) memory. The TDS3000 series doesn't do much better with only 10k points. Serial protocol decode is pretty much useless with these short memories.

--- End quote ---
Don't confuse the TDS 2000/3000 series with the much newer DPO or MSO 2000 / 3000 series. Both use plugin I2C EEPROM modules for options, but that's where the similarity ends. The DPO/MSO series have deep memory and other modern features.

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