WHat will happen if one of the ADC channel is removed from the couple of connected ADC channels?

[Ljohn]

Hi,

i have a problem with controller stm32f030c8t6 where i have connected two ADC channels to read the sensor values(Temperature &humidity). if i remove one of the ADC channel from the sensor output pins i will get fluctuating values from minimum to maximum (0 - 3.3v(ref.voltmax)).

If i remove the the both channels it will show 0v in the pins.

please let me know the slution.

thanks in advance,

Lidiya John.

[Ozone]

> if i remove one of the ADC channel from the sensor output pins i will get fluctuating values from minimum to maximum (0 - 3.3v(ref.voltmax)).

For floating inputs, you get floating result values.

Because of the structure of multiplexed SAR - ADCs, they depend on the result of the preceeding channel (last converted) as well.

> If i remove the the both channels it will show 0v in the pins.

You have no preceeding channel, and no charge on the S&H capacitor.

> ... if i remove one of the ADC channel from the sensor output pins i will get fluctuating values ...

> please let me know the slution.

Don't do this.

[Ljohn]

🙂 ..

Actually these are the testing scenarios.

1.With two sensor values

2. without 2 sensor values

3.either one of the sensor is not working/removed.

[Ozone]

> Actually these are the testing scenarios.

So, this exposes an inherent problem with either your hardware, or your software.

Your sampling time could be too short, causing cross interferences.

If you want "safe" analog inputs, use two ADC channels per input, preferably on separate ADCs, and cross-check both values.

[Ljohn]

Thank you.. for the information ..👍