Switchable Gain with Offset

[JochiSt]

When the sensor is heated, the current is e.g. 20mA, by this the voltage created by this is 2V. This means, that the resistance changes are biased with this

Similar to the gain switching amplifier #9 a bias, which is subtracted would be ideal.

This can be achieved with a similar structure.

The voltage can be generated by e.g. two additional timer channels.

[JochiSt]

The resistive divider of R7 and R8 is not strictly needed. It also works without these two resistors. Also removing them might simplify the calculation.

[JochiSt]

Using a analog switch yields a better result (see b1855a238db8a5da4ba2636cf99099591b647a84)

[JochiSt]

Using a CD4066, the amplifier can now be biased. There is one bias for CH0 and one for CH1. I've the hope, that the I and U bias match. Otherwise, some resistors might be needed here.