| 摘要 |
A system for determining the position of a piston (68) moveable within a cylinder, or of an implement (12) or a joint, is disclosed herein. Electromagnetic (EM) bursts such as ultra-wideband or frequency pulses are generated and applied to a transmitter/receiver unit (78). The EM bursts are launched by the transmitter along a transmission guide from an end of the cylinder housing (42) towards the piston (68). The transmission guide can be a dipstick (70) mounted within the cylinder housing (42) or the cylinder housing (42) itself. The dipstick (70) or cylinder housing (42) is in electrical communication with the piston (68) such that a surface of the piston (68) represents an electrical impedance discontinuity which causes the EM burst to be reflected back to the receiver. The time for the EM burst to travel from the transmitter to the piston (68) and for the reflections to travel back to the receiver is determined and converted into a position signal (118) represeting the piston's position. A compensation signal (126) can be used to compensate the position signal (118) for variations in a parameter of the fluid within the cylinder such as dielectric constant caused by factors such as temperature, contamination and fluid type. The compensation circuit (122) can include a pulse level analyzer, resonance circuit, capacitance circuit, compensation dipstick (146), or second transmitter/receiver (142) circuit configured to measure the piston's position from the opposite end of the cylinder. |
