Abstract: A processing apparatus is configured to receive a sense signal from a capacitive fluid sensor having a first electrode and a second electrode with a sensing region between the electrodes. The processing apparatus is configured to receive an alternating drive signal applied to the capacitive fluid sensor. The processing apparatus is configured to determine a complex impedance of the fluid sensor based on the sense signal and the drive signal. The complex impedance includes an in-phase component indicative of a conductivity quantity of a fluid in the sensing region and a quadrature component indicative of a capacitance quantity of the fluid sensor. The processing apparatus is configured to determine a temperature of the fluid in dependence on at least the determined capacitance quantity of the fluid sensor.

Abstract: Apparatus for measuring at least one property of a fluid comprises a capacitive fluid sensor (110) comprising a first electrode (111) and a second electrode (112) with a sensing region (113) between the electrodes. The apparatus comprises an alternating signal source (120) configured to apply an alternating drive signal to the capacitive fluid sensor (110). The apparatus comprises a processing apparatus (200) configured to receive a sense signal from the capacitive fluid sensor (110) and the alternating drive signal. The processing apparatus (200) is configured to: determine a complex difference signal comprising an in-phase difference component between the drive signal and the sense signal and a quadrature difference component between the drive signal and the sense signal; determine the at least one property of the fluid based on both the in-phase phase difference component and the quadrature difference component of the difference signal.

Abstract: A processing apparatus (700) is configured to receive a sense signal from a capacitive fluid sensor (610) comprising a first electrode (611) and a second electrode (612) with a sensing region (613) between the electrodes. The processing apparatus (700) is configured to receive an alternating drive signal applied to the capacitive fluid sensor (610). The processing apparatus (700) is configured to determine a complex impedance of the fluid sensor (610) based on the sense signal and the drive signal, the complex impedance comprising an in-phase component indicative of a conductivity quantity of a fluid in the sensing region and a quadrature component indicative of a capacitance quantity of the fluid sensor. The processing apparatus (700) is configured to determine a temperature of the fluid in dependence on at least the determined capacitance quantity of the fluid sensor (610).

Abstract: Apparatus for measuring at least one property of a fluid comprises a capacitive fluid sensor (110) comprising a first electrode (111) and a second electrode (112) with a sensing region (113) between the electrodes. The apparatus comprises an alternating signal source (120) configured to apply an alternating drive signal to the capacitive fluid sensor (110). The apparatus comprises a processing apparatus (200) configured to receive a sense signal from the capacitive fluid sensor (110) and the alternating drive signal. The processing apparatus (200) is configured to: determine a complex difference signal comprising an in-phase difference component between the drive signal and the sense signal and a quadrature difference component between the drive signal and the sense signal; determine the at least one property of the fluid based on both the in-phase phase difference component and the quadrature difference component of the difference signal.