Abstract: A circuit for simulating a capacitance fuel probe, the circuit comprising: an input for receiving an alternating current (AC) excitation signal; an output for outputting an output signal representing a capacitance of the simulated fuel probe; a single reference capacitance; a first amplifier connected to the reference capacitance, the first amplifier being configured to cause a current flow through the reference capacitance; a second, variable gain, amplifier, the second, variable gain amplifier being configured to output an AC signal representing a multiple of the current flow through the reference capacitance, wherein the AC signal output by the second amplifier is used to generate the output signal.

Abstract: A filter for use with a brushless DC motor to filter a signal received from a floating terminal of the brushless DC motor, wherein the filter is configured such that a time delay introduced by the filter to the signal received from the floating terminal is equal to the time taken for a rotor of the motor to rotate through an angle equal to half of a commutation step of the motor.

Abstract: A circuit for simulating a capacitance fuel probe, the circuit comprising: an input for receiving an alternating current (AC) excitation signal; an output for outputting an output signal representing a capacitance of the simulated fuel probe; a single reference capacitance; a first amplifier connected to the reference capacitance, the first amplifier being configured to cause a current flow through the reference capacitance; a second, variable gain, amplifier, the second, variable gain amplifier being configured to output an AC signal representing a multiple of the current flow through the reference capacitance, wherein the AC signal output by the second amplifier is used to generate the output signal.

Abstract: A filter for use with a brushless DC motor to filter a signal received from a floating terminal of the brushless DC motor, wherein the filter is configured such that a time delay introduced by the filter to the signal received from the floating terminal is equal to the time taken for a rotor of the motor to rotate through an angle equal to half of a commutation step of the motor.

Abstract: An aircraft fuel-gauging system has multiple gauging sensors in each tank divided into two groups. Each group of sensors connects with a respective processor. The processors are linked to provide a display in the cockpit to give an indication of fuel quantity derived from all the sensors. The two processors also provide separate, nominally-identical display indications of fuel quantity on a refuel panel on the exterior of the aircraft. The refueller can compare these two separate quantity indications with the flow meter in the fuel dispenser to confirm that the correct quantity has been dispensed.

Abstract: A capacitance fuel-gauging system has a capacitive probe and a reference capacitor charged in opposite senses from respective dc voltage sources via switches operated in antiphase. Two further switches alternately discharge the capacitors to a 0 volts rail. The outputs of the probe and the reference capacitor are connected to a summing node, which is connected to an amplifier via a pair of switches operated in antiphase to rectify the output. The amplifier connects to a processor, which controls the relative outputs of the voltage sources and provides an output indicating the value of the probe.

Abstract: A capacitance fuel-gauging system has a capacitive probe and a reference capacitor charged in opposite senses from respective dc voltage sources via switches operated in antiphase. Two further switches alternately discharge the capacitors to a 0 volts rail. The outputs of the probe and the reference capacitor are connected to a summing node, which is connected to an amplifier via a pair of switches operated in antiphase to rectify the output. The amplifier connects to a processor, which controls the relative outputs of the voltage sources and provides an output indicating the value of the probe.