A proximity sensor for sensing the proximity of a target comprising: an electrical component for sensing the proximity of the target, said electrical component having electrical properties that vary with the proximity of the target; an impedance component (21) having a known impedance and a first end connected to a first end of said electrical component; a switch (31) connected to switch between said first end of said impedance component (21) and a second end of said impedance component (21); a signal generator connected to said second end of said impedance component (21) for generating an electrical signal for application to the impedance component and electrical component; an analogue-to-digital converter for receiving an electrical signal and for generating a digital signal; and a processor connected to the analogue-to-digital converter for receiving a digital voltage signal and for generating a proximity signal, wherein said processor (23) is adapted to control said switch to switch (31) to connect to said first and second ends of said impedance component sequentially.