Instek GDS-840C worth it? - Page 1
Forum section: electronics / general

author: guitar309
author_rank: Contributor
timestamp: December 23, 2010, 04:30:07 am
content: I have been looking at a used Instek GDS-840C ... Its 250mhz ... but other then that.. is it a decent scope? I understand it is worth more.. and costly.. but would I be better off spending the money on a new cheaper scope like rigol or the instek 1062... how do you think this Instek GDS-840C stacks up to newer scopes on the market?

author: Bored@Work
author_rank: Super Contributor
timestamp: December 23, 2010, 09:29:18 am
content: You haven't told us the price for this used GDS-840C. How should we judge if the price is OK if we don't know the price?In general, the GDS-800 series is the oldest DSO series from Instek on the market. If I am not mistaken it is their first DSO series. The "C" at the end indicates a color display. It tells you something about the age of the oscilloscope when a color display was still worth to mention explicitly.The GDS-800 series was followed by the GDS-2000, GDS-1000, GDS-1000A, and recently the GDS-3000 series (in that order). If I see the signs right, then Instek hasn't completely dropped the GDS-800 series, but is about to do so.The GDS-800, like the GDS-2000 series are a more old-fashioned oscilloscopes. They are bulkier than the later 1000, 1000A, 3000 series or the current Rigols, UNI-Ts, Hanteks, etc. They are rack-mountable. It doesn't have a lot of acquisition memory, compared to current oscilloscopes, and only has an RS232 interface, not USB.I probably would only buy anewGDS-840C if I needed some of its special features, like it being rack-mountable, having a more robust metal chassis as opposite to the typical plastic these days, or if I would need the go/no-go feature. But otherwise anewGDS-840C isn't very attractive. Without knowing the price for yourusedGDS-840C it is impossible to say if yourusedGDS-840C is attractive.

author: guitar309
author_rank: Contributor
timestamp: December 23, 2010, 04:24:08 pm
content: 350 dollares.. tested and 100 % in working order..

author: saturation
author_rank: Super Contributor
timestamp: December 23, 2010, 09:15:31 pm
content: Its a decent price, the key item is that since its older, its Ms/s and memory length are less than newer scopes; ~$400 US buys a 50 MHz Rigol 1052E or an Instek 1062A at 60 MHz both do 1Gs/s versus 100Ms/s for the 840C. The Rigol has a long memory of 1M points for single channel at 500Ms/s , 512K points each for both channels using 500Ms/s, 1Gs/s at 16K points, versus 125K each for both channels of the 840C sampling at 100Ms/s. The 1062E does 2M points single channel, 1M points each for 2 channels, sampling at 1Gs/s.Memory and sampling speeds are major determinants of how well the DSO capture signals with analog like fidelity, so is the aliasing error good enough for your application?http://www.evaluationengineering.com/index.php/solutions/instrumentation/understanding-long-memory-in-a-dso.htmlhttp://www.picotech.com/applications/oscilloscope_tutorial.htmlQuote from: guitar309 on December 23, 2010, 04:24:08 pm

author: Unknown
author_rank: Unknown
timestamp: December 23, 2010, 10:24:52 pm
content: 250MHz analog bandwidth, but only 100MS/s according to my 10s of research. Single shot bandwidth is about 10-20MHz. The full analog bandwidth is only useful for repetitive signals (which rules out most digital signals, for example). IMO you're better off with a recent scope that has less bandwidth, but can actually make use of this bandwidth in most cases. Unless you've a specific need for the 250MHz and can stand the disadvantages, go for newer technology. If it's actually Instek's first DSO, it may also have issues like aliasing or lousy user interface.