[Tinyos-help] TelosB ADC input

[PETTA NICOLO']

Good morning,

I have a problem with TelosB ADC input.

I need reading four different values on ADC input. So I use a selector that switches over a voltage divider powered by the Analog VCC (pin 1 of the 10-pin expansion connector) and closed over the Analog Ground (pin 9 of the 10-pin expansion connector). The output of the selector represent the ADC’s input. 

 

I know that the input impedance of ADC is 1 MΩ.

I use 1 KΩ resistors to make the divider, but I find the ADC input voltage is always about 0 Volt, as if it is grounded. 

 

Can someone tell me why it doesn’t work correctly? Where do I make mistake?

I am at your disposal for further clarifications.

 

Thank you very much for your attention. 

 

 

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Nicolò Petta

 

 

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