Forgive my stupidity and lack of knowledge, but I understand that due to impedance on the ADC, that the sensors spec for use with the ADC should be 10k max. Any suggestions for reliably utilising sensors that are often in the 100 - 500K range? Is it a question of interfacing with an external ADC or buffering something. Don't think that makes any sense, but it might mean something to someone? Cheers
10K is the optimum input impedance, that is not saying that other values will not work.
The simplest way if you find you are having trouble is to use an emitter follower or source follower using an extra transistor or FET. To lower the impedance to 10K.
I would say 10k is the maximum, not optimum. A unity-gain op-amp buffer would be a simple way to start interfacing these types of high-impedance sensors.
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For safety reasons I once used a serial 100k in the analog lines... That was no good at all...
I use opamp buffers, that seems to do the trick and you can get them in a SOT23-5 pack so they are no larger than a transistor.
This IS overkill.... A low power rail-to-rail, I hope?