Design Con 2015
Breaking News
Blog

Assessing scope accuracy

NO RATINGS
View Comments: Threaded | Newest First | Oldest First
Bert22306
User Rank
CEO
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
Rookie
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
Nanette Collins continues on her quest to educate engineers about the value of good PR and marketing.
Patients who use tablets to access to their own care information and communicate with doctors and call nurses are more satisfied.
Engineers at Mentor Graphics provide an introduction to design-for test that explains the underlying concepts used in DFT software and automated test.
Ethernet has a growing role in automotive and industrial networks as long as security is addressed, says the chief technology officer of Vitesse Semiconductor.
Becoming a measurement master, like anything else, takes time and effort.
Most Recent Comments
sempaiscuba
 
mithrandir
 
sempaiscuba
 
sempaiscuba
 
sempaiscuba
 
sempaiscuba
 
sempaiscuba
 
sempaiscuba
 
sempaiscuba
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