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Making a basic auto-gain circuit (like an oscilliscope on auto mode)

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What would the best method be for taking an input signal (0vdc to 15vdc), isolating it, and then measuring it accurately?

I am thinking like an oscilloscope, where you can hook up pretty much anything and it will automatically adjust the gain and read the input correctly.

Would a simple DC only case like mine be solved with a few fixed comparators finding and finding a range that the input signal is in, then measure using the upper comparator limit as the reference?
 

It depends on the lowest voltage and the accuracy you want. You can simple measure 0-15V with an ADC, but not if you want to measure 1mV with 16 bit accuracy. A programmable gain instrumentation amplifier is one option. Just adjust the gain until the output is within your ADC range.

Keith
 

The automatic operation of the Auto-Scale feature in a digital oscilloscope is achieved by a processor and related firmware rather than simple hardware logic. If you do it in hardware, you should at least implement a comparator hysteresis to prevent the circuit from switching the gain continuously.
 

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