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Oscilloscope measurment error?

I measure some behaviours of ferroresonant circuit and the main goal of measurment is to determine for which amplitude of AC voltage source i get current with doubled frequency compared with frequency of source.

Well, i must determine for which E of voltage source E*sin(2*pi*f*t) i get current with frequency 2*f...

I only can detect this behaviour with looking on oscilloscop to see waveform of current and with increasing of E to determine the moment (and, of course, value of E) in which frequency of current becomes 2*f...

I made this measurments but my problem is to calculate measurment error (unrealibility?).. If i measure something with voltmeter i have in its specifications data about its inrealibility/error and then i can write measurment result something like this:

measured voltage= 5V +- 10%, or measured voltage= 5V +- 0.5V...

But how to determine this value (+-10% or +-0.5V) for oscilloscope at which im looking and waiting to see doubled frequency of current...?

Thanks...

P.S. It would be easier if i had "Frequencymeter" but i dont have it and because of that i must determine wanted value E only with Oscilloscop-display and with my eyes waiting for 2f frequency of current...

Reply to
Krunom
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"Krunom" wrote in news:cgf3op$b88$ snipped-for-privacy@bagan.srce.hr:

Your scope's manual should have the specifications for timebase and vertical gain accuracies. Analog scopes are generally 2 or 3 % within the center graticule divisions. Outside of that center area,the accuracies may be much worse.

--
Jim Yanik
jyanik-at-kua.net
Reply to
Jim Yanik

That is listed in the Oscilloscope specs, and then you have to eyeball it, so that can be 3% too.

Reply to
murgatroid

"Krunom" writes: ...

Many oscilloscopes have specifications for their error. But often these depend on your having had your scope calibrated recently, having had your scope turned on and warmed up for a sufficient period of time, etc.

See if you have had your scope calibrated recently and if there are accuracy specifications available for it.

Sometimes you can get a less accurate estimate of this by using a known good amplitude calibration signal of about the same waveform and amplitude, measure that and determine the error, and assume the same error will be present in your actual measurements.

Reply to
Don Taylor

Thanks to all for replies...

Its calibrated and i have the specifications. But there is small complication about the measurment. Ill describe shortly measurment process: Im increasing manualy E (AC voltage source: E*sin(2Pi*f*t)) and im looking current wave form at oscilloscope display and waiting to see that the frequency of current equals 2*f (double source frequency) and then im reading the value of E (at the display of some other instrument). Now should i write result something like this:

E=10V+-0.1V.

I know that all instruments have influence on measurment error, but i want to know what is the influence of Oscilloscope because im not using any "numeric" values from oscilloscope, im only "looking" at display and waiting to recognize "frequency of current" = 2*"source frequency"...

Should i simply use error-data from oscilloscope-manual or is it more complicated because of subjective nature of measurment: "...im only "looking" at display and waiting to recognize"... hmmm.. im waiting to recognize... what is my "error"....? maybe is this the main question...

I hope its more clear now...

Thanks...

Reply to
Kruno Milicevic

What is the bacndwith of the scope and at which frequency are you measering? Do not forget that the bandwith of a scope is specified at the -3db point. So the amplitude error could be 30% ....

-bent

Reply to
Dombo

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