Electronics > Projects, Designs, and Technical Stuff
Why are oscilloscopes so inaccurate?
drummerdimitri:
I realized how inaccurate my scope was when doing some DC measurements of a battery compared to my 6.5 digit DMM so I thought the unit needed calibration until I read the datasheet which shows a 2% voltage accuracy which is worse than the cheapest DMM on the market today.
Why is this the case? Even Keysight's Infiniium UXR scopes which can cost up to 1M $ have the same accuracy as my cheap Rigol.
capt bullshot:
Because one uses a cheap DMM to measure a battery.
Rerouter:
I would say that in general they are more concerned with AC performance, however if your DC is so far off, run a self cal on the scope, in most cases this should put you well under 1% for DC offset and for most should also reduce any gain errors, however I will warn that some scopes seem to only calibrate there AC coupled mode or there DC coupled mode, and do not store offsets for both (there are small offsets between these 2 on most front ends)
The other one is , in most scopes your only dealing with an 8 bit ADC, now you can use the channel offset in a lot of cases to squeeze out extra precision, but in the end most scope measurements are relative, with repeatability being more valuable than absolute accuracy.
If you want a faster, high precision ADC, that gets into purpose built test gear like keithley DAQ's, as to why the 1 million dollor scopes DC specs are poor, they are not intended to be used in that application, they needed the best bandwidth / sample rate and AC performance, how well it measured a slow DC signal was very much an afterthought.
tggzzz:
--- Quote from: drummerdimitri on August 10, 2019, 10:23:03 am ---I realized how inaccurate my scope was when doing some DC measurements of a battery compared to my 6.5 digit DMM so I thought the unit needed calibration until I read the datasheet which shows a 2% voltage accuracy which is worse than the cheapest DMM on the market today.
Why is this the case?
--- End quote ---
You might as well ask why an oxy-acetylene torch is hotter than a soldering iron. Different tools for different jobs, each with different necessary strengths and allowable weaknesses.
Choose the right tool for the job, work around the limitations of available tools.
mikerj:
Why is my DMM useless for showing high frequency time domain behaviour? |O
Navigation
[0] Message Index
[#] Next page
Go to full version