frequency & Amplitude measurement

[garg29]

I want to measure Frequency & Amplitude of a Triangular/Square/Sine-wave. Is there any dedicated IC for this, which may give digital or voltage output proportional to the above parameters.

Regards.

 

[ashugtiwari]

As far as i know, u can use following methods:
1. to find the frequency, pass any periodic wave from comparator and convert that periodic wave to square wave, the output square wave from comparator then feed to CCP module capture unit and find the period count from capture timer. This will tell u the period of signal. Inverse it to find frequency of signal.
2. use a op-amp based precision rectifier to rectify any input periodic wave, filter it to find the average or rms value, use the formula for rms or average to find the peak value of voltage.
3. use ADC to sample the signal at higher sampling rate twice of signal freq. Find the max from sample values to find the amplitude. Also, u can find the freq of input signal from FFT of ADC time domain samples. After taking FFT, just find the maxima in the 0 to N/2 range, the maxima is the frequency of signal.

Hope that helps.

 

[garg29]

Thats fine but there are lots of issues in that method, like accuracy, temperature deviation, linearity, noises etc. I was thinking if there was a dedicated chip for this job (i think there must be a one). Anyway still Thanks a lot for your reply & efforts.

 

[ashugtiwari]

its a vary vague answer, but still may be helpful:
op-amps generally have temperature deviation information for different operating voltage, u can find a correction coefficient from it.
as of accuracy, noises, these are mostly contributed to layout design of PCB. Use IC's with better SNR to attain better accuracy and noise protection.
linearity depends on temperature and SNR, so u can use curve fitting correction for that and generate linearity curve.

using micro-controller like PIC24/30/33F or MSP430 series, u can make a control system to compensate all these parameters in software and achieve higher precision. Other than that, I don't know any one single IC which does all that. Try searching digikey.

hope that helps.

 

[garg29]

Thanks a lot. You seem to have good technical knowledge. . a guess from your name i think you may be from India... Happy Holi.
Why do you suggest PIC24/30/33F or MSP430.... any particular reason....I'm using PIC16/18 series
Can you share your mobile no. with me I'll call you...

 

[ashugtiwari]

The PIC16/18 is good when the amount of calculations are low, but if they increase too much like in curve fitting, SNR, temp compensation etc etc it is better to go for PIC24 (like PIC24FV16KM204) which has internal fractional and integer single cycle multiplier.
But i think PIC18 is enough for ur application.

Yes im from India.
Thanks for holi wishes and same to u, plz check and send me private messages if u wish to contact me.
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