Embedded Systems Conference
Breaking News
Blog

Assessing scope accuracy

NO RATINGS
View Comments: Oldest First | Newest First | Threaded View
Bert22306
User Rank
Author
re: Assessing scope accuracy
Bert22306   2/20/2012 9:01:23 PM
NO RATINGS
That's kind of an age-old question. It's not JUST about accuracy. It's also about whether you change the measurement appreciably by just touching probes to the circuit. IMO, every EE who's actually an EE has had this drilled into him throughout school and career, and has been bitten when he ignored the issue. Sometimes the absolute number isn't all that important, but what always matters is whether the scope, voltmeter, ammeter, whatever, is making the measurements irrelevant. Sort of a macro version of Heisenberg's uncertainty principle.

sharps_eng
User Rank
Author
re: Assessing scope accuracy
sharps_eng   2/20/2012 9:57:12 PM
NO RATINGS
You have to be careful when doing differential measurements (x-y) with the iNVERT function, there is no standard for where the summing takes place. Many (all?) cheap LCD scopes just subtract the pixels, so although what you see is what you get, if one of the signals clips the screen edge the diff signal is meaningless. Decent analog scopes (and some were quite cheap also) used to let you have seriously high gains which would overload each channel on their own, but when summed, cancelled the inputs so that you could get a good high-resolution view of a small signal which was superimposed on a large one (like a 100mVp-p crosstalk transient on a 24V DC supply). Its worth checking this on any scope purchase. Of course, you will eventually build a decent diff pre-amp yourself, but until then, a good ADD-plus-INVERT on your scope is very handy.

More Blogs
The right design framework and RTOS can help simplify and cost-reduce creation and certification of safety-critical software.
A new study comparing the Intel X86, the ARM and MIPS CPUs finds that microarchitecture is more important than instruction set architecture, RISC or CISC.
2015 is a wonderful year for anyone who has a special interest in time or simply experiences its passage.
To make its affinity-based RTOS scheduling algorithm for multicore software both testable and flexible, Green Hills is using LDRA’s lightweight code coverage tools.
At some point in the life of a technology startup company, the CEO and the founding team will be confronted with the question of whether to sell the company or not. Hopefully, the question arises in a positive context and comes from an interested buyer driven by the opportunity to deploy the new technology to a much larger user base.
Flash Poll
Like Us on Facebook

Datasheets.com Parts Search

185 million searchable parts
(please enter a part number or hit search to begin)
EE Times on Twitter
EE Times Twitter Feed
Top Comments of the Week