frequency comparator needed

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adutzu07

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Can anyone help me to make a frequency comparator? I need to compare 2 frequencies and to make them equal in case one of them is change. A point of start is to have a reference frequency. If other frequency changes, I need to bring it back to it's start value that is the reference frequency. :|
 

Hello,

Is what you want a PLL (phased locked loop), or do you require an analog output voltage proportional to the frequency difference?
 

Hello and I'm glad to have a response on my question.

I don't know if it's a PLL circuit. I want to bring my frequency that changes back to it's initial value. I want to recalibrate my device to function on it's initial frequency. For example I have a device that has an oscillator on 10 MHz, and that device works fine with that oscillator frequency. If I came with some materials that affect that oscillator, the frequency of that oscillator is lower that the initial one, and the device that I use with this oscillator stop working.
How can I do to have a normal function on that device and in case if my oscillator is perturbed ?
 

Hello,

I think I don't fully understand what you mean. Are you aligning an oscillator so that it has (almost) same frequency as some other master or reference, and after the alignment, there is no link between the oscillators (so a PLL is no option)?

When this is the case, you could use a frequency counter, but another way is to use mixing (frequency beating), or a dual channel oscilloscope. What is the maximum allowable frequency offset between the two devices?
 

for frequency detector in PLL, google "rotational frequency detector" or Phase frequency detector.
 

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