Portable precision electronic caliper

• US 6,332,278 B1
• Filed: 11/08/1999
• Issued: 12/25/2001
• Est. Priority Date: 05/09/1997
• Status: Expired due to Term

• Current Assignee: Tesa Sa (Hexagon AB)
• Original Assignee: Brown & Sharpe Tesa Sa (Hexagon AB)
• Inventors: Bezinge, Alex, Bolli, Jean-Luc
• Primary Examiner(s): Bennett, G. Bradley
• Application Number:
  US09/435,353
• Time in Patent Office: 778 Days
• Field of Search: 337/08, 337/83, 337/84, 338/13, 338/18, 338/19, 338/20, 338/23, 338/24, 338/31, 324/207.11, 324/207.13, 324/207.24
• US Class Current: 33/784
• CPC Class Codes: G01B 3/205 provided with a counter for digital indication of the measured dimension
• CPC Class Codes: G01D 5/2451 Incremental encoders G01D5/2454 takes precedence

Abstract

Portable precision caliper comprising a slide (2) and a shaft (1) each fitted with a jaw (10, respectively 20). The slide is further equipped with electronic means (11) which enable the distance between the jaws (10, 20) to be displayed on an electronic display (12). The electronic means are powered by a battery (110, 111). The shaft (2) is fitted with a magnetized scale (21) with a period of magnetization λ. The electronic means (11) include a sensor (112) equipped with an array of magnetoresistive electrodes disposed opposite said scale (21). The resistance values of the magnetoresistive electrodes are a sinusoidal function of the longitudinal position of the sensor (112) along the scale (21). The set of magnetoresistive electrodes includes at least certain sets of magnetoresistive electrodes formed of at least 8 electrodes connected in series, so as to increase the electric resistance of the sets and to reduce the electricity consumption of the whole device.

Claims

1. A portable electronic precision caliper comprising:

a shaft fitted with a magnetized scale having a period of magnetization λ

,

a slide that is displaceable longitudinally along said shaft, the slide and the shaft each having a jaw,

an electronic circuit mounted on said slide and being powered by a source which is internal to said portable electronic precision caliper, said electronic circuit comprising a single sensor,

said sensor comprising an array of n magnetoresistive electrodes disposed opposite said scale so that values of resistances of the magnetoresistive electrodes are a function of their longitudinal position along the scale, n being greater than two,

said magnetoresistive electrodes being integrated in said sensor,

said electronic circuit being able to determine, from the values of resistance of the magnetoresistive electrodes, information depending on a gap between said jaws and to display this information on said electronic display.

2. The caliper according to claim 1, wherein said array of magnetoresistive electrodes comprises a plurality of sets of magnetoresistive electrodes connected in series.

3. The caliper according to claim 2, wherein a number of magnetoresistive electrodes connected in series in each said set is greater than 8.

4. The caliper according to claim 3, wherein a thickness of the magnetoresistive electrodes is less than 100 nm, a length of the magnetoresistive electrodes is between 0.1 and 10 millimeters and a width of the magnetoresistive electrodes is less than 40 μ

m.

5. The caliper according to claim 4, wherein the dimensions of the magnetoresistive electrodes, their material and their number per set are chosen so that the resulting resistance of each said set of magnetoresistive electrodes is greater than 10 kΩ

.

6. The caliper according to claim 5, wherein the dimensions of the magnetoresistive electrodes, their material and their number per set are chosen so that the resulting resistance of each said set of magnetoresistive electrodes is greater than 50 kΩ

.

7. The caliper according to claim 3, wherein said magnetoresistive electrodes are spread longitudinally over at least two periods of magnetization λ

of the scale.

8. The caliper according to claim 7, wherein said sets of magnetoresistive electrodes comprise electrodes occupying positions spread between kλ

−

w/2 and kλ

+w/2,

wherein k is a whole number and w is a parameter indicating the spread of electrodes of each set.

9. The caliper according to claim 2, wherein said sets of magnetoresistive electrodes connected in series are connected to define at least one measuring bridge, and wherein said electronic circuit uses a signal or signals at an output of said measuring bridge or bridges to determine a distance of said gap between said jaws.

10. The caliper according to claim 9, wherein a number of magnetoresistive electrodes per set is greater than 8.

11. The caliper according to claim 10, wherein a thickness of the magnetoresistive electrodes is less than 100 nm, a length greater than 0.1 mm and a width of the magnetoresistive electrodes is less than 40 μ

m.

12. The caliper according to claim 11, wherein the dimensions of the magnetoresistive electrodes, their material and their number per set are chosen so that the resulting resistance of each said set of magnetoresistive electrodes is greater than 10 kΩ

.

13. The caliper according to claim 12, wherein the dimensions of the magnetoresistive electrodes, their material and their number per set are chosen so that the resulting resistance of each said set of magnetoresistive electrodes is greater than 50 kΩ

.

14. The caliper according to claim 8, wherein said sets of electrodes connected in series are connected to define two measuring bridges, and wherein said electronic circuit uses signals at an output of said measuring bridges to determine a distance of said gap between said jaws.

15. The caliper according to claim 14 wherein a voltage applied to said measuring bridges is reduced when said caliper is in a stand-by mode.

16. The caliper according to claim 15, wherein the voltage applied to said measuring bridges in said stand-by mode is sufficient for detecting a displacement of the slide.

17. The caliper according to claim 14, wherein the magnetoresistive electrodes constituting the second measuring bridge are phase-shifted by λ

/4 with respect to the magnetoresistive electrodes making up the first measuring bridge, so that signals at the two bridges'"'"' outputs are phase-shifted by 90°

with respect to each other.

18. The caliper according to claim 17, wherein said magnetoresistive electrodes are spread longitudinally so as to constitute x groups of magnetoresistive electrodes, said groups being spaced by λ

/4 and comprising at least two magnetoresistive electrodes of a same set connected in series.

19. The caliper according to claim 1, wherein a distance between the magnetized scale and the magnetoresistive electrodes is between 0.2 and 0.7 millimeters, and wherein the period of said scale is between 0.5 and 1.5 millimeters.

20. The caliper according to claim 19, wherein said magnetoresistive electrodes are spread longitudinally over at least two periods of magnetization λ

of the scale.

21. The caliper according to claim 20, wherein said magnetoresistive electrodes are spread longitudinally over at least 3 millimeters.

22. The caliper according claim 1, wherein at least certain magnetoresistive electrodes are provided with barber-pole structures.

23. The caliper according claim 22, wherein said magnetoresistive electrodes are provided with barber-pole structures with several different orientations.

24. The caliper according to claim 9, wherein said sensor further comprises at least one compensation resistance of said measuring bridge or bridges, whose value is adjustable by a laser during manufacture so as to balance said measuring bridge when no magnetic field is applied.

25. The caliper according to claim 1 wherein said electronic circuit is arranged on a printed circuit board, and wherein said magnetoresistive sensor is disposed on a side of the printed circuit opposite said scale.

26. The caliper according to claim 25, wherein said electronic circuit includes a permanent magnet mounted on the side of the printed circuit board opposite the scale, close to said magnetoresistive electrodes, so as to modify a direction and amplitude of a magnetic field resulting on said magnetoresistive electrodes.

27. The caliper according claim 26, wherein said magnetoresistive sensor is coated with a synthetic protective layer opposite said scale.

28. The caliper according to claim 26, wherein said slide is of metal, wherein said printed circuit board is affixed directly on said slide so that the magnetoresistive electrodes of said magnetoresistive sensor are at a predetermined distance of the scale, wherein the slide is further provided with a shockproof coating of synthetic material over said printed circuit, an opening being provided through said shockproof coating for fitting said electronic display.

29. The caliper according to claim 1, wherein said electronic circuit further comprises an accumulator and a linear generator, a displacement of said slide along said magnetized scale generating a current in said linear generator, said current recharging said accumulator, and said accumulator powering said electronic circuit.

30. The caliper according to claim 1, wherein said shaft and said slide are of aluminum whereas said scale is of steel.

31. The caliper according to claim 30, wherein said scale is coated with a non-magnetic protective layer.

32. The caliper according to claim 31, wherein said protective layer bears markings indicating at least approximately the position of the slide along the shaft.

33. A portable electronic precision caliper, comprising:

a shaft fitted with a magnetized scale having a period of magnetization λ

,

a slide that is displaceable longitudinally along said shaft, the slide and the shaft each having a jaw,

an electronic circuit mounted on said slide and being powered with an internal power source, said electronic circuit comprising a single sensor,

said sensor comprising an array of n magnetoresistive electrodes disposed opposite said scale so that values of resistances of the magnetoresistive electrodes are a function of their longitudinal position along the scale, n being greater than two,

said electronic circuit being able to determine, from the values of resistance of the magnetoresistive electrodes, information depending on a gap between said jaws and to display this information on said electronic display,

said array of magnetoresistive electrodes consisting of a plurality of sets of magnetoresistive electrodes each comprising at least 8 electrodes connected in series, a thickness of the nagnetoresistive electrodes being less than 100 nm, a length of said magnetoresistive electrodes being between 0.1 and 10 millimeters and a width of said magnetoresistive electrodes being less than 40 μ

m, so that a resulting resistance of each set of magnetoresistive electrodes is greater than 10 kΩ

, so that said caliper can be powered with an internal power source.

34. The caliper according to claim 33, wherein said magnetoresistive electrodes are spread over at least two periods of magnetization λ

of the scale,

wherein the resulting resistance of each set of magnetoresistive electrodes is greater than 50 kΩ

, said electronic circuit using signals at an output of said measuring bridges to determine a distance between said jaws,

said sets of magnetoresistive electrodes connected in series being connected to define two measuring bridges to determine the distance between said jaws.

35. The caliper according to claim 34, wherein the magnetoresistive electrodes constituting the second measuring bridge are phase-shifted by λ

/4 with respect to the magnetoresistive electrodes making up the first measuring bridge,

wherein said magnetoresistive electrodes are spread longitudinally so as to constitute x groups of magnetoresistive electrodes, said groups being spaced by λ

/4 and comprising at least two magnetoresistive electrodes of a same set and connected in series,

so that the signals at the two bridges'"'"' output are phase-shifted by λ

/4.

36. The caliper according to claim 33, wherein a distance between the magnetized scale and the magnetoresistive electrodes is between 0.2 and 0.7 millimeters,

the period of magnetization λ

of the scale being between 0.5 and 1.5 millimeters,

said magnetoresistive electrodes being spread longitudinally over a length greater than or equal to two periods of magnetization λ

of the scale and greater than or equal to 3 millimeters.

37. The caliper according to claim 33, wherein at least certain magnetoresistive electrodes are provided with barber-pole structures with several different orientations.