Signal generating apparatus and method

• US 5,886,559 A
• Filed: 08/09/1995
• Issued: 03/23/1999
• Est. Priority Date: 04/23/1992
• Status: Expired due to Fees

• Current Assignee: Rolls Royce and Associates Ltd (Rolls-Royce Holdings Plc)
• Original Assignee: Rolls Royce and Associates Ltd (Rolls-Royce Holdings Plc)
• Inventors: Berrill, Michael J
• Primary Examiner(s): Callahan, Timothy P.
• Assistant Examiner(s): Luu, An T.
• Application Number:
  US08/513,114
• Time in Patent Office: 1,322 Days
• Field of Search: 327/334, 327/343, 327/538, 327/352, 327/355, 327/361, 327/407, 327/408, 327/99, 327/403
• US Class Current: 327/334
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06
• CPC Class Codes: G01D 5/2515 with magnetically controlled switches, e.g. by movement of a magnet
• CPC Class Codes: G01D 5/252 a combination of conductors or channels
• CPC Class Codes: G01F 23/72 using magnetically actuated indicating means
• CPC Class Codes: G01F 23/74 for sensing changes in level only at discrete points

Abstract

Signal generating apparatus comprises a linear series of Hall-effect switches (44) arranged as a plurality of linear arrays in discrete probes (46a, 46b . . . 46n) which are butted end to end. Each switch is closed when in proximity of an actuating magnet (40) movable along the series of switches. In each array a resistance chain (66) is linked at intervals to the switches. Movement of the magnet along an array thereby gives a progressively changing voltage on an output line (5) from the resistance chain as a cumulative signal indicating the position of the magnet. When the magnet moves from one array to the succeeding array after generating a maximum cumulative signal from said one array, that signal is maintained by a latch connection (56) between the two arrays. A cumulative signal representing the magnet position relative to the complete series of switches can thus be generated. The arrays are powered in parallel so that it is possible to extend substantially the total number of switches or indicating points in the in the apparatus.

Claims

1. A signal generating apparatus comprising means for inputting a plurality of variable input signals to produce a cumulative output signal and means for selectively varying the number of said inputs, impedance-changing means in the lines of the respective input signals for providing a substantially constant impedance for the cumulative output signal independent of the number of said inputs.

2. Apparatus according to claim 1 wherein said impedence changing means comprises a plurality of resistance branches, each resistance In each branch being in series with a respective input signal and all the resistances being connected to a common output for the cumulative signal, means for opening the circuit between the inputs and said common output for the resistances to which no inputs are to be applied, and means varying the resistances In those lines to which the inputs are to be applied in dependence on the number of said inputs.

3. Apparatus according to claim 2 wherein the resistance in the path of each input signal line comprises a series of similar value resistors the total number of which in each line corresponds to a maximum number of said input signals.

4. A signal generating apparatus comprising means for summing a plurality of input signals to produce a cumulative output signal and means for selectively varying the number of said inputs, variable impedance means in the lines of the respective input signals for providing a substantially constant impedance for the cumulative output signal independent of the number of said inputs, said variable impedance means comprising a plurality of resistance branches each having plurality of resistances, each resistance in each branch being in series with a respective input signal and all the resistances being connected to a common output for the cumulative signal, means for opening the circuit between the inputs and said common output for the resistances to which no inputs are to be applied, and means varying the resistances in those lines to which the inputs are to be applied In dependence upon the number of said inputs, the resistances in the path of each input signal comprising a series of similar value resistors, the total number of resistors In each line corresponding to a maximum number of input signals.