Beginners ADC offset question

there is no such thing as ADC unless you are talking about Aid to Dependent Children.

please re-read your question and then restate it in such a way that we may answer it.

Not a problem, in theory and quite possibly easy in practice. You simply need to sum your input signal with a very stable dc offset voltage before presenting it to the ADC.

This could be as simple as a potentiometer (multi-turn is possible a good idea) and capacitor. The pot goes between a stable positive supply voltage and ground and its wiper goes to both the input of the ADC and to a capacitor connected to your input signal. Adjust the wiper to give the 1.65v offset needed to bring the zero point of the input signal up to the mid-range voltage of the ADC.

Or it could be something a lot more complex - it depends on the accuracy of measurement that you need and the bandwidth and source impedance of your input signals. For example, you may need to build a quite complex, low noise, reference voltage generator plus a complex low noise analogue buffer amplifier to match the impedance of the source.

If your processor has a PWM with a max output 3.3V just set the PW to 50% and feed it into the ADC through a high pass filter maybe a 300ohm Res and a .1uF Cap. The noise from the PWM will give you a small amplitude sine wave.

Other folks do not have issue with ADC, which stays for Analog-To-Digital Converter in any book. Keep reading the forum - it will come to you.

TimPerry wrote:

, i'd type that as A/D converter.

i thought this was gonna be another thing about alternating DC.

On Sat, 21 Oct 2006 01:45:14 -0400 TimPerry wrote: | snipped-for-privacy@hotmail.com wrote: |> Other folks do not have issue with ADC, which stays for |> Analog-To-Digital Converter in any book. Keep reading the forum - it |> will come to you. | | , i'd type that as A/D converter.

I see both of these ways to refer to it about 50/50.

| i thought this was gonna be another thing about alternating DC.

DC transformers and AC batteries.

Ignition coils. Batteries made from unobtanium. :-)

Ed