digital scopes and frequency of an input signal

[Digital-L0gik]

Frequency

Hi does anyone know how digital scopes measure and calculate the frequency of an input signal? What sort of circuitry is needed to measure frequency?

 

[Aya2002]

Frequency

i do not know deep but i think you need a frequency counter

 

[patweadock]

Re: Frequency

A couple of ways I know of;
Sample the waveform with a analog-to-digital-converter (ADC) and plot the results on a screen. The maximum rate of sampleing for todays ADCs is a few million a second, so it would not work above 1 Mhz, because you'de only have a couple of points per wavelength.
The way it's done by todays digital scopes is by using samples taken over many wavelengths and then using an ingenious formula called the fourier transform (Fourier Analysis) to "convert from the time domain to the frequency domain" The formula is basic arithmatic, but a whole lot of it, so most DSPs (digital signal processors) will perform a "Fast Fourier Transform". It outputs not only the primary frequencies , but all the component or harmonic frequencies and their amplitute relative to the primary, into a numerical file. From this the digital scope constructs the waveform with it's frequency. These scopes are limited by their sampling rate, as far as accurate waveforms.

 

[yanzixuan]

Re: Frequency

Hi does anyone know how digital scopes measure and calculate the frequency of an input signal? What sort of circuitry is needed to measure frequency?

the easy way is make a counter,and let the input signal trig it for 1s(or less).then the value of counter is the frequency.

 

[Digital-L0gik]

Re: Frequency

Good information guys, thanks for the help!