We are using C8051F970 Capsense modules. We received a new sensor sheet from a customer. The sheet is to be used for measuring water level. It is highly sensitive and causes the sensor input to overflow/saturate. We reduced the sensor gain to 1 which reduced its sensitivity. However it still saturates far earlier than required (After a water height of 70cm).
The obvious approach is to modify the sensor sheet to lower the sensitivity.
However if this is not possible is there anyway to reduce the sensor sensitivity further via firmware/software.
The current sensor output goes from 20000->65520.
One thought process, is this 20,000 could be considered 0. The idea is it would start measuring from 20,000 onwards. Rather than 20,000->65520, it could do 0->65,520 (+20,000). I guess this is all dependent on hardware, register design.
I think the answer to this is already no, but I have been asked to confirm. Is it possible to change sensitivity at run time.
if changing the sheet is 'impossible' (nothing is) there is another solution:
go old fashioned, forget the capsensens circuitry, short the cap with an open drain IO feed the cap through a resistor from a push-pull IO, measure with the ADC after a given time
It turned out there was problem with the sensor case (water leak). When that was repaired, the overflow problem disappeared.
The gain setting is a register setting, so a real change should not be an issue.