controller Charge Pump?

[Luciano]

Hi,

See attached BMP file.

Nernst-cell internal resistance (Ri) measurement.

The circuit measures the resistance of the Nernst-cell and
also the resistance of the RiCall 82.5 ohm. Both measurements
are done with the same I/O, so we measure with the same voltage
when we source (+4.xx V) and when we sink (0.xx V).
The PWM is not used.

The AC current is ≤ 250 µA.
(See 250 µA current direction when the I/O sink or source).

The differential amplifier will output a voltage when
Ri and RiCall have different values.The output voltage is
measured with the A/D of the MCU. With the resistors you
can adjust the gain of the amplifier.

* * *

The Tech Edge does almost the same with the I/O but
they use a 910 ohm resistor so the current is more
than 250 µA. (???). The capacitor is the 100nF C201.
They use 2V as the virtual ground.

(See page 6 of the PDF for Max. current load of the Nernst-cell).
http://wbo2.com/lsu/Y258K01005e03mar21eng.pdf

* * *

This is just a theoretical circuit.
Never been tested.

Luciano