By changing the reference analogReference (INTERNAL) we will achieve a resolution of 1.1/1024 ie ~1 mV.
How to improve it to 0.5 mV or even better ?
Whether changing analogReference (EXTERNAL) and connecting AREF to 500 mV will serve the purpose ?
Help is required...in this regard.
What is lowest voltage Arduino UNO analog pins can measure...?
What voltage range do you intend on measuring? I assume it will be <= 500mV if your hoping to use external reference in this range.
A word of warning. If your connecting a reference voltage to the external reference pin then do not do an analogRead() before you have set analogReference (EXTERNAL)
You can read multiple times to get higher precision. READ - http://www.atmel.com/images/doc8003.pdf -
in essence you make 4 reads, divide the sum by 2 to get ~1 bit extra (~11 bits 0..2046)
16 reads, divide sum by 4 gives ~2 bits extra (~12 bits 0..4092)
uint16_t ADC12(int pin)
{
uint16_t sum = 0;
for (int i=0; i<16; i++) sum += analogRead(pin);
return sum/4;
}
Note that taking 16 samples will take 2..3 milliseconds, so the input signal should be stable for that period.
best is of course to amplify the signal to 0..5V if possible.
The lowest voltage recommended for AREF is 1V I think, according to the datasheet - in other
words you'll just get poor performance at lower reference voltages, any extra precision will
be spurious.
Amplify your signal or use an external 12+ bit ADC.
By the way what is your actual problem?
Riva:
What voltage range do you intend on measuring? I assume it will be <= 500mV if your hoping to use external reference in this range.A word of warning. If your connecting a reference voltage to the external reference pin then do not do an analogRead() before you have set analogReference (EXTERNAL)
Yes approximately 500 micro Volt is my target. Without any amplifier whether Arduino UNO can do it ?
Whether changing analogReference (EXTERNAL) and connecting AREF to 500 mV, whether i will get 500mV/1024 = ~488 microVolt ? s it possible..?
MarkT:
The lowest voltage recommended for AREF is 1V I think, according to the datasheet - in other
words you'll just get poor performance at lower reference voltages, any extra precision will
be spurious.Amplify your signal or use an external 12+ bit ADC.
By the way what is your actual problem?
If we are using analogReference(EXTERNAL) it was seen in the datasheet that we can supply 0 to 5V range to AREF pin. Whether a voltage of 500 mV to AREF is possible to improve resolution to 500mV/1024 = 488 micro Volt. Whether i am right or wrong?
I would like to know the lowest voltage that can be measured at analog input pins of Arduino UNO.
In some case i am not able to amplify signals from some sensors, thats the reason for my doubt...
anuigcar:
Yes approximately 500 micro Volt is my target. Without any amplifier whether Arduino UNO can do it ?
Whether changing analogReference (EXTERNAL) and connecting AREF to 500 mV, whether i will get 500mV/1024 = ~488 microVolt ? s it possible..?
From what MarkT said I looked at the datasheet and it says min value for VREF is 1.0 volts so it looks like you really need to amplify the signal to get the resolution your looking for. I suspect that ADC noise would have fairly decimated your ADC reading accuracy if 0.5V was an option.