Control and/or measurement method of periodic waveform?

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posted
15 years ago

Fri, Apr 3, 2009 11:31 PM

I've decided to build, for personal use, a waveform generator based on the AD5930. I'll be able to adjust the output over a 50mv to 20 VPP range - my question is how do I measure the amplitude of the output with any precision? I can either measure (peak detector) the output or control it. For the second option, I'm thinking about using a TI VCA810, driven by an DAC, which has a gain adjust range of +- 40dB. The first option is easy to implement, however it suffers from a lack of accuracy - especially over the frequency and amplitude range I want to cover. The second option looks the most attractive; however it also has it's drawbacks (gain is linear with dB - NOT v/v - so I'll have to try to do Logs in ASM on a micro ) - my primary goal is the accuracy of the measurement. So, any suggestions? Is there an option that I'm overlooking? Thanks for the help...

Hal

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- John Larkin
  
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posted
15 years ago

Sat, Apr 4, 2009 3:23 AM

DVM? Oscilloscope? RF voltmeter?

The ADI part has an amplitude adjust pin... why not use it? You could follow it with a step attenuator to make the really tiny signals.

John

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- whit3rd
  
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posted
15 years ago

Sat, Apr 4, 2009 7:18 PM

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Depends how much precision you want, but the internal reference and converter are probably accurate enough as long as you never change the "FSADJUST" pin. There are multiplying DACs that will take the waveform as reference and output any fraction from 0 to 255/256 of the full range (old CMOS designs, like AD7524).