Pulse echo distance measurement
AssigneeCroma Developments Limited
InventorRoger Fell
Life of this patent
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Abstract
The invention concerns pulse echo distance measurement and in particular a method and apparatus for calculating such a distance by sensing multiple reflections of a given pulse signal. By sensing multiple reflections, and not just the primary echo, internal time delays which would otherwise cause systematic errors may be simply eliminated and the multiple readings obtained may be utilized to provide system self-diagnostic checks, eliminate spurious information and provide an accurate measure of distance. A particular advantage of the method is that very small distances between sensor and target may be measured.
Claims10
A method for measuring a distance between a sensor surface and a target, the method comprising the steps of:
- stimulating a pulse transmitter to transmit a pulse signal from the sensor surface towards the target;
- and
- sensing a plurality of echoes, said plurality of echoes comprising a) an echo reflected from the target to the sensor and received by a pulse receiver to generate a pulse received signal at a corresponding echo arrival time and b) an echo reflected at least once from the sensor surface to generate a further pulse received signal with a respective arrival time;
- and
- determining the time delay between the pulse received signals to therein give a value proportional to the time taken for the pulse to travel from the sensor surface to the target and, a distance between the sensor surface and the target,
- wherein an arrival time, t.sub.n of an echo corresponding to that of a transmitted pulse which is being reflected n times by the target is given by the following equation:
- t.sub.n =t.sub.t +t.sub.r +2.multidot.t.sub.p +2n.multidot.t.sub.x
- where, t.sub.t represents a time delay between applying a stimulate transmission electronic signal to a transmitter and the generation of a pulse, t.sub.p represents the time taken for the pulse to propagate through a sensor body, t.sub.x the time taken for the pulse to travel from a sensor surface to the target and t.sub.r represents the time delay between a pulse arriving at the receiving element and the generation of a pulse received signal.
Apparatus for measuring the distance between a sensor surface and a target, the apparatus comprising:
- a pulse transmitter arranged on receiving a stimulate transmission signal to transmit a pulse signal from the sensor surface towards the target;
- a pulse receiver arranged to sense echoes of the pulse received at the sensor surface and generate pulse received signals;
- and
- control means coupled to each of the transmitter and the receiver, wherein said pulse receiver senses a plurality of echoes, said plurality of echoes comprising an echo reflected from the target to the sensor and received by said pulse receiver to generate a pulse received signal at a corresponding echo arrival time and an echo reflected at least once from the sensor surface to generate a further pulse received signal with a respective arrival time and said control means for determining the time delay between the pulse received signals to give a value proportional to the time taken for the pulse to travel from the sensor service to the target and, a distance between the sensor surface and the target, wherein an arrival time, t.sub.n of an echo corresponding to that of a transmitted pulse which is being reflected n times by the target is given by the following equation:
- t.sub.n =t.sub.t +t.sub.r +2.multidot.t.sub.p +2n.multidot.t.sub.x
- where, t.sub.t represents a time delay between applying a stimulate transmission electronic signal to the pulse transmitter and the generation of a pulse, t.sub.p represents the time taken for the pulse to propagate through a sensor body, t.sub.x the time taken for the pulse to travel from a sensor surface to the target and t.sub.r represents the time delay between a pulse arriving at the receiving element and the generation of a pulse received signal.
Dependencies are inferred from the claim text.