ADC Input Zero Voltage when channel disconnected

[tiwari.sachin]

Hello,

I need to know how can I make a input channel to the ADC as zero when no input is connected.

My circuit works fine when I have a signal connected at the input channel and the results are accurate. When when I donot connect any sensor, the values read are random and it is understandable as it is open. I would want to make this pin zero when no sensor is connected.

How can I achieve this.

Regards
Sachin

 

[godfreyl]

Connect a resistor between input and ground.

 

[tiwari.sachin]

Using a pull down will make it act like a voltage divider when the sensor is connected. I can use a very high value but the same shall still be a problem as the accuracy of the signal will still reduce a bit.

 

[Tunelabguy]

Using a pull down will make it act like a voltage divider when the sensor is connected. I can use a very high value but the same shall still be a problem as the accuracy of the signal will still reduce a bit.

Yes, but you cannot have an infinite input impedance and still guarantee that random static charge will be drained away. Anyway, you should be driving the A/D input with a very low output impedance from the sensor, so the voltage divider effect can be reduced to less than one LSB.