Strange ADC behaviour

[Acetronics2]

NO NO NO DON'T DO IT

Vref have to be lower than Vdd. Let's see you have a sensor who produce you a max of 1 volt. Then you select a Vref of ~1 Volt, then your ADC give you the full 10 bit conversion scale between 0-Vref. This is the use of it.

Hi, Steve

a LM 385 or 385-1.2 will make a nice ( and cheap ! ...) 1.235 v reference here ...

BUT, do not forget the higher the signal ... the smaller the noise ! ( and last digit flickering ! ) ...
so, here, the sensor choice is " not so good" ... If I understood (?) , our friend wants to read ambiant temp ... 150-250 mv levels !


( note an OPA will amplify noise + signal ... "not so good" solution too ...)

Alain