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I am looking for an AGC (Automatic Gain Control) which outputs not only the normal output but also another output which tells you what gain it is using. I need this for an automatic voltage meter I am building; it doesn't have to be an AGC just some kind of device which changes its output voltage if the input voltage is out of the scale I am measuring, but tells me the gain so I can know the input voltage. I was thinking maybe comparators that if I pass a certain voltage it changes a voltage divider.

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  • \$\begingroup\$ Forgot to mention I need to measure AC and DC \$\endgroup\$ – S.Korai Jul 18 '16 at 6:17
  • \$\begingroup\$ Not exactly an answer but if you build your own with a VCO and an external feedback mechanism for the servo, you can tap out the said control signal easily. \$\endgroup\$ – winny Jul 18 '16 at 8:01
  • \$\begingroup\$ Attack times? Hold times? Release speed? AGCs need more parameters so think about this a little and do some research on the web. \$\endgroup\$ – Andy aka Jul 18 '16 at 8:35
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    \$\begingroup\$ AGC or PGA (Programmable Gain Amplifier)? A PGA has discrete precision gain steps, similar to the ranges of a DVM. If you really are trying to make an auto-ranging DVM function, each PGA range needs its own offset & gain calibration. \$\endgroup\$ – MarkU Jul 18 '16 at 9:46
  • \$\begingroup\$ @Andyaka I was more interested in if such a thing exits in the market and less about specific one. \$\endgroup\$ – S.Korai Jul 19 '16 at 16:14
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The approach that springs to mind is to input a small high frequency sine on top of your regular input signal, band pass to find out how big it is, and then high pass to get rid of it. It means you can't low pass at your amplifier, but it's fairly straightforward.

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