ANALOG-DIGITAL SHAFT POSITION ENCODER

• US 3,670,324 A
• Filed: 03/27/1970
• Issued: 06/13/1972
• Est. Priority Date: 03/27/1970
• Status: Expired due to Term

• Current Assignee: Trevor, 3rd
• Original Assignee: Trevor, 3rd
• Inventors: Trevor, 3rd
• Primary Examiner(s): Robinson, Thomas A.
• Application Number:
  US05/023,270
• Time in Patent Office: 809 Days
• Field of Search: 340/347AD
• US Class Current: 341/6
• CPC Class Codes: H03M 1/30 incremental

Abstract

Encoding equipment in which the output signals of a position encoder such as a shaft position encoder are sampled for counting only during a short sampling period in each cycle of the output signals. The sampling period is determined by a signal from a clock source, and the clock source is used to synchronize the operation of the entire counting system. Thus, the chances that spurious counts will be created by spurious signals is minimized. The shaft encoder preferably produces two trains of output pulses in quadrature. The output pulses are counted by an up-down counting system which displays a digital number representing the shaft position together with a plus or minus sign to indicate the direction in which the shaft has been rotated.

Claims

1. A shaft position encoder including transducer means for producing two trains of data pulses in quadrature with respect to one another, with one of said trains leading the other during shaft rotation in one direction, and lagging the other during shaft rotation in the other direction, the number of pulses in each train representing the relative shaft position in a particular direction, means for up-down counting of said data pulses to digitally indicate the shaft position, a clock source for enabling said counting means, said clock source having a frequency substantially greater than that at which said data pulses are developed, means for enabling said counting means for only a relatively small portion of each clock pulse cycle, means for incrementing or decrementing said counting means in accordance with the leading-lagging relationship between said trains, and for indicating the leading or lagging relationship and thus indicating the direction of rotation of the shaft.

2. An encoder as in claim 1 including means for visually displaying the count on said counting means and visually indicating the direction of rotation of said shaft.

3. An encoder as in claim 1 including divide-by-two circuit means for dividIng in half the frequency of said data pulses prior to their being counted.

4. An encoder as in claim 1 in which said clock source frequency is at least twice the maximum frequency of said data pulses.

5. An analog-to-digital shaft position encoder including means for converting the relative shaft position into data pulses whose total represents said position, a bi-directional counter for counting said data pulses and indicating said total, means for indicating the direction of change of said shaft position and, for each such data pulse incrementing or decrementing said counter in accordance with said direction of change, and means for causing the indication of the direction of change to reverse upon a transition of the signal from said direction change indicating means.

6. An encoder as in claim 5 including a clock source for enabling the delivery of said pulses to said counter at a rate substantially higher than the rate at which said pulses are developed.

7. An encoder as in claim 6 including means controlled by said clock source for enabling said delivery for only a small fraction of a cycle of the clock signal.

8. An encoder as in claim 5 including means for storing one logic state of said converting means, means for comparing the succeeding logic state of said converting means with said one logic state and incrementing or decrementing said counter in response to the detection of a change in said logic state.

9. An encoder as in claim 8 in which said encoder includes a transducer which produces two quadrature pulse trains which lead or lag one another in accordance with the direction of change of said position of said shaft.

10. An encoder as in claim 5 including means for detecting and indicating when said shaft is in its zero reference position.