Detecting negative voltages with SAADC

[Noah]

Hi! I am going to work on a project that uses a specific sensor which produces voltage outputs between 250 mV and -250 mV. Can someone help me with ideas to detect the negative voltages with the nRF52810 SAADC? Are there SAADC options I can set via software related to offset, or would this best be handled with a hardware/electronics solution? I cannot lose resolution of the sensor, the full range must still be 500 mV (i.e. I cannot map the 250 mV to -250 mV output to land with a 250 mV to 0 mV range). 

Any advice would be super helpful! Thanks

[Turbo J]

AIN pins cannot go below 0V (GND) - thus you will need to shift your signal to be in 0V...VCC range.

We don't know enough yet in order suggest a specific circuit (e.g. using opamps or instrumentation amps).

[haakonsh]

You need to know the output impedance of your sensor and the maximum and minimum frequencies you wish to resolve. 

[Noah]

What would I do once I know the output impedance of the sensor? And what do you mean by max/min frequencies, it is an iridium oxide pH sensor which produces a varying voltage output based on pH of solution. I would like to take 20-30 samples to average per reading, and perform one reading every 15 minutes or so

[haakonsh]

Do you have a datasheet of the sensor?
 

Noah said:

What would I do once I know the output impedance of the sensor?

 Choose a suitable DC bias circuit.

Noah said:

And what do you mean by max/min frequencies, it is an iridium oxide pH sensor which produces a varying voltage output based on pH of solution.

 Then I guess you have no more than a few Hz as the max frequencies.