[Tinyos-help] Voltage of AVcc pin on Tmote Sky-Pin1

[manu suryavansh]

Hi,
Thanks Michael.
I am using the 1.5V reference, I want to know how much does the reference voltage varies. I am planning to use a voltage regulator if it varies much, because Tmote allows to use external reference. As the sensor output is between 0-10mV I am getting very low resolution so either I have to lower the reference or amplify my signal. Usually sensor outputs are low voltage so what is generally done and how a constant supply is maintained?
Any suggestions?
Thank you
Manu Suryavansh
UFL

Michael Schippling <schip at santafe.edu> wrote: If the telos is like the mica's the AVcc pin is pretty much the battery
supply, so 2.9v is reasonable. Is there a spec someplace that says it
should be 2.5v?

If the above is true it's actually a feature...yes, a ratio-metric sensor
is a voltage divider, and the output will change with the supply voltage.
But (on the mica's at least) the ADC reference voltage is tied to the
battery and droops by the same amount, so they remain (mostly) calibrated
to each other.

tricky design...do you think it was intentional?
MS

manu suryavansh wrote:
> Hi,
> I measured the voltage of the AVcc pin on tmote sky using a multimeter 
> and it shows to be 2.9 volts. Is it not supposed to be 2.5 volts?- I 
> want to use that pin to give supply to my sensor but if that voltage 
> keeps varying then output will not be correct because the sensor is 
> ratiometric and its output depends on the power supply. Is this the 
> correct way to do this?
> Any suggestions will be helpful.
> Thank you
> Manu Suryavansh
> University of Florida
> 
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