No, that won't reduce the 12V, you should have something like this:
If there's 12V on divider VCC, there should be 2.4V on SIG and ADC value should be 491.
No, that won't reduce the 12V, you should have something like this:
If there's 12V on divider VCC, there should be 2.4V on SIG and ADC value should be 491.