# Successive Approximation ADC binary output

#### x1222

Joined Oct 22, 2011
31
I built Successive approximation ADC. As I crank up the voltage, the ADC output starts counting up binary. What is the binary output suppose to tell me? Is there anyway to convert that into readable voltage value?

#### joeyd999

Joined Jun 6, 2011
4,477
I built Successive approximation ADC. As I crank up the voltage, the ADC output starts counting up binary. What is the binary output suppose to tell me? Is there anyway to convert that into readable voltage value?
You built an S/A ADC from scratch? Or you build a circuit using an off-the-shelf ADC?

Can't help you in the first case: only you would know the answer.

In the second case, usually you define a Vref, where the maximum number of digital counts out occurs when Vin=Vref. Then for any Vin<Vref, counts = Vin/Vref * 2^n where n is the number of bits.

So, for, say an 8 bit ADC with a Vref of 2.56V, there will be 256 possible output values (0 to 255), each count representing a 10mV increase in Vin.