Take the logger PCB and sensor out of the outer housing. Take a flat screw driver and push on the edge of the sensor on the solid outer steel ring (see picture). This is somewhat obstructed by a flange inside the outer tube casing but with a little care you can get between the flange and the sensor ring.

Simultaneously pull on the PCB by the IR diodes. Don't twist the PCB when pulling on it as this will just result in twisting the wires connecting the PCB and the sensor.