METHOD FOR CONFIGURING A CALIBRATION MECHANISM AND FORCE SENSOR THEREOF

Abstract

A method for configuring a calibration mechanism in a force sensor (100) has the steps of: coupling an end of the calibration lever (1071) to a loading end (102) of the force sensor; adjusting, in a no-load condition, the center of gravity (G.sub.0) of the unloaded calibration lever (1071), so that the center of gravity (G.sub.0) lies on a horizontal line (H) through the center of a calibration lever fulcrum (1031) at a fixed end (103) thereof; and adjusting, in a full-load condition, the center of gravity (G.sub.1) of the calibration lever (1071) loaded with the calibration weight (106), so that the center of gravity (G.sub.1) lies on the horizontal line (H) through the center of the calibration lever fulcrum. The calibration error caused by inclination in the force sensor is reduced by practice of this method.

Claims

1. A method for configuring a calibration mechanism in a force sensor, comprising the steps of: coupling an end of a calibration lever to a loading end of the force sensor; adjusting, in a no-load condition, a center of gravity of the calibration lever, so that the center of gravity lies substantially on a horizontal line which goes through a center of a calibration lever fulcrum at a fixed end of the force sensor; and adjusting, in a full-load condition, the center of gravity of the calibration lever loaded with a calibration weight, so that the center of gravity lies substantially on the horizontal line which goes through the center of the calibration lever fulcrum.

2. The method of claim 1, wherein in the no-load condition, an enclosed acute angle between a line connecting the center of the calibration lever fulcrum and the center of gravity with the horizontal line is between −2° and +2°; and in the full-load condition, the enclosed acute angle between a line connecting the center of the calibration lever fulcrum and the center of gravity with the horizontal line is between −2° and +2°.

3. The method of claim 1, comprising the further step of: configuring the center of gravity of the calibration lever with the calibration weight or without the calibration weight, so that the respective center of gravity is positioned distant from the coupled end of the calibration lever for loading the calibration weight and close to the center of the calibration lever fulcrum.

4. The method of claim 1, comprising the further step of: coupling the end of the calibration lever to a fulcrum located at the loading end of the force sensor.

5. A force sensor, comprising: an elastic body, comprising a fixed end and a loading end for loading the weight of an object to be weighed, with an intermediate part being provided between the fixed end and the loading end, wherein the intermediate part being provided with a transducer mechanism for converting the weight loaded on the loading end of the elastic body into a weighing signal; a calibration mechanism capable of applying a calibration force on the loading end; the calibration mechanism comprising a calibration weight a calibration lever being connected to the fixed end via a calibration lever fulcrum; wherein the calibration mechanism is configured according to the method of of claim 1.

6. The force sensor of claim 5, wherein the calibration lever includes an adjusting device for adjusting the position of the center of gravity of the calibration lever.

7. The force sensor of claim 6, wherein the centre adjusting device comprises at least one counterweight loading part provided on the calibration lever.

8. The force sensor of claim 5, further comprising: a weight loading mechanism for loading the calibration weight to the loading end of the calibration lever and unloading the calibration weight from the loading end of the calibration lever.

9. The force sensor of claim 5, further comprising: an inclination sensor for sensing an inclination of the force sensor relative to a horizontal plane, wherein the force sensor compensates a calibration weighing value output by the force sensor based on the inclination sensed by the inclination sensor.

10. The force sensor of claim 5, wherein the transducer mechanism comprises a strain gauge sensor.

11. A weighing apparatus, comprising at least one force sensor according to claim 5; wherein: a calibration weighing value and an inclination value are obtained when the internal calibration mechanism of the force sensor is loaded with a calibration weight; a calibration compensation value is calculated from the calibration weighing value and the inclination value, and a calibration weighing value is outputted by the apparatus which has been corrected according to the calibration compensation value.

12. The force sensor of claim 5, wherein the transducer mechanism comprises a capacitive pressure sensor.

13. The force sensor of claim 5, wherein the transducer mechanism comprises an optical sensor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The above-mentioned and other features, properties and advantages of the present invention will become more apparent from the following description of the embodiments with reference to the accompanying drawings, and the same reference numerals denote the same features throughout the figures, in which:

[0045] FIG. 1 is a schematic isometric view of a force sensor according to one embodiment of the present invention;

[0046] FIG. 2 is a schematic perpendicular cross-sectional view of a lever of the force sensor in FIG. 1 in the state of an unloaded calibration mechanism;

[0047] FIG. 3 is the same schematic perpendicular cross-sectional view of the force sensor in FIG. 2 with a lever in the state of a loaded calibration mechanism;

[0048] FIG. 4 is a schematic isometric view of a weighing apparatus with a cross-sectional cut off with the force sensor shown in FIG. 1;

[0049] FIG. 5 is a schematic isometric view of a force sensor according to another embodiment of the present invention;

[0050] FIG. 6 is a schematic perpendicular cross-sectional view of a lever of the force sensor in FIG. 5 in the state of an unloaded calibration mechanism.

DETAILED DESCRIPTION OF EMBODIMENTS

[0051] The present invention will be further described below by way of examples, but the present invention is not therefore limited to the scope of the described embodiments.

[0052] In the process of loading/unloading calibration weights by the loading mechanism of a force sensor, the alignment of the lever gravity centre related to the position of the lever fulcrum is configured and controlled to be approximately on the same horizontal line, so that calibration errors caused by an inclination of the force sensor or an inclination of the internal calibration mechanism are reduced, and an inclination of the force sensor sensed by an angle sensor, like an inclination sensor, is also used for further compensation of the calibration, thereby maintaining the accuracy of the force sensor.

[0053] Hereinafter, the implementation of the present invention will be illustrated by way of examples via the following embodiments.

[0054] In the embodiment shown in FIGS. 1-4, according to the weighing apparatus, among two ends of the elastic body 101 of the force sensor 100, there is a fixed end 103 fixed to a base panel A and a loading end 102 provided with a tray B. The two ends of the elastic body 101 are connected by two parallel beams 104 parallel to each other. A set of strain gauges are provided on the parallel beams 104.

[0055] A calibration lever 1071 of the internal calibration mechanism is formed between the parallel beams 104, connected to the fixed end 103 at the lever fulcrum 1031 and the calibration lever 1071 rotates around the fulcrum 1031. The calibration lever 1071 also connects to the loading end 102 by a loading lever fulcrum 1021 when calibrating the force sensor.

[0056] An end portion of the calibration lever 1071 extending beyond the loading end 102 and is provided with a V-shaped weight bracket. A calibration weight 106 can be placed in the weight bracket and the V-shaped weight bracket can prevent the calibration weight 106 from sliding and shaking in the weight bracket.

[0057] In this embodiment, a loading mechanism 105 is fixed to the base panel A and is provided on the side of the loading end 102 which loads the calibration weight 106 on the weight bracket or unloads the calibration weight 106 from the weight bracket by a lifting movement as shown in FIGS. 2 and 3.

[0058] When configuring on the calibration mechanism in this embodiment, firstly, the calibration lever 1071 is coupled to the loading fulcrum 1021 located at the loading end 102 of the force sensor. After the coupling, the gravity centre G.sub.0 of the calibration lever 1071 is adjusted in a no-load condition to lie substantially on a horizontal line H which goes through the centre of the calibration lever fulcrum 1031, when the calibration lever 1071 is unloaded. The gravity centre G.sub.1 of the calibration lever 1071 together with the calibration weight 106 is adjusted in a full-load condition to lie substantially on the horizontal line H which goes through the centre of the calibration lever fulcrum 1031 when the calibration weight 106 is loaded on the calibration lever 1071 by the loading mechanism 105.

[0059] In this embodiment, as shown in FIG. 3, after the loading mechanism 105 loads the calibration weight 106 onto the calibration lever 1071, the centre-of-gravity position of the calibration lever loaded with the calibration weight 106 is G.sub.1. A horizontal line H as shown is defined by having the level of the calibration lever fulcrum 1031. A straight line connecting the lever gravity centre G.sub.1 and the calibration lever fulcrum 1031 is below the horizontal line H and forms an acute angle of −2° with the horizontal line H.

[0060] In another configuration setting, the straight line connecting the calibration lever gravity centre G.sub.1 and the calibration lever fulcrum 1031 is above the horizontal line H and forms an acute angle of +2° with the horizontal line H. In another variation, the calibration lever gravity centre G.sub.1 and the calibration lever fulcrum 1031 are on the horizontal line H, that is, the straight line connecting the gravity centre G.sub.1 and the calibration lever fulcrum 1031 coincides with the horizontal line H in the environment where the force sensor 100 is located.

[0061] In those settings, the acute angle formed between the straight line connecting the calibration lever gravity centre G.sub.1 and the calibration lever fulcrum 1031 and the horizontal line H is controlled between −2° below the horizontal line and +2° above the horizontal line H. In this case, the calibration error caused by the inclination of the calibration lever is controllable, which reduces the influence on weighing accuracy.

[0062] When configuring the calibration mechanism, before the loading mechanism 105 loads the calibration weight 106 onto the calibration lever 1071 or after the calibration weight 106 is unloaded from the calibration lever 1071, the calibration lever gravity centre G.sub.0 of the calibration lever 1071 the calibration lever fulcrum 1031 are on the same horizontal line H, that is, the straight line connecting the calibration lever gravity centre G.sub.0 and the calibration lever fulcrum 1031 coincides with the horizontal line H in the environment where the force sensor 100 is located.

[0063] In another configuration setting, the straight line connecting the calibration lever gravity centre G.sub.0 and the calibration lever fulcrum 1031 is above the horizontal line H and forms an acute angle of +2° with the horizontal line H. In another variation, the straight line connecting the calibration lever gravity centre G.sub.0 and the calibration lever fulcrum 1031 is below the horizontal line H and forms an acute angle of −2° with the horizontal line H.

[0064] As the setting mentioned above, when the calibration lever 1071 is unloaded, the included angle formed between the straight line connecting the centre-of-gravity position G.sub.0 of the calibration lever 1071 and the lever fulcrum 1031 and the horizontal line H is controlled between −2° below the horizontal line H and +2° above the horizontal line H. The controllability of the calibration error caused by the inclination of the calibration lever is further improved, and the influence on weighing accuracy is reduced.

[0065] In another embodiment, as shown in FIGS. 5 and 6, the calibration lever 1071 is further provided with counterweight loading holes 10711. As shown in FIG. 5, in one counterweight loading hole 10711 a counterweight 108 is inserted so that the counterweight 108 is loaded on the calibration lever 1071, thereby further fine adjusting the lever gravity centre of the calibration lever 1071 and enabling the calibration lever gravity centre and the calibration lever fulcrum 1031 to be located on the same horizontal line H as much as possible. Moreover, two counterweight loading holes 10711 are provided on the calibration lever 1071, on which counterweights of other weights can be hung and loaded.

[0066] In another embodiment, counterweight loading parts are provided at different positions of the calibration lever and each counterweight loading part has at least one counterweight hole or counterweight loading position, respectively. The structure of counterweight loading part formed by two counterweight loading holes in this embodiment can be more simplified, for example, the calibration lever has only one counterweight loading position or loading through-hole, etc.

[0067] The force sensor 100 of this embodiment is further provided with an inclination sensor (not shown). The inclination sensor can be provided on the fixed end 103 of the force sensor 100 to sense the inclination of the force sensor 100 relative to the horizontal plane.

[0068] In this embodiment, when the force sensor 100 performs a calibration, the calibration weight 106 is loaded onto the V-shaped weight bracket. Using the leverage transmission rate of the calibration mechanism, the loading force, a multiple of the calibration weight, is applied to the loading end 102, and the strain gauge converts the loading force into an electrical signal of the calibration weighing value. Then, in this embodiment, the calibration compensation value is calculated by using the calibration weighing value and the inclination value sensed by the inclination sensor, and the calibration weighing value is further corrected by the calibration compensation value. Thereafter, the weighing output of the force sensor 100 is calibrated using the calibration weighing value to maintain the accuracy of the force sensor 100.

[0069] A platform scale of another embodiment comprises four force sensors 100 of the above embodiments. After the platform scale sends calibration instructions to each force sensor 100, each force sensor 100 performs internal calibration operations, such as loading internal calibration weights and outputting calibration weighing values, and then unloading the internal calibration weights. During the internal calibration operation, the inclination value is sensed at the same time.

[0070] The platform scale receives the calibration weighing value and the inclination value from each force sensor 100, and a processing unit of the platform scale completes the calculation and correction of the calibration weighing value and further calibrates the weighing output of the platform scale.

REFERENCE SIGNS LIST

[0071] 100 Force sensor [0072] 101 Elastic body [0073] 102 Loading end [0074] 1021 Loading lever fulcrum [0075] 103 Fixed end [0076] 1031 Calibration lever fulcrum [0077] 104 Parallel beam [0078] 105 Loading mechanism [0079] 106 Calibration weight [0080] 1071 Calibration lever [0081] 10711 Counterweight loading hole [0082] 108 Counterweight [0083] A Base panel [0084] B Tray [0085] G.sub.0 Lever gravity centre of the unloaded calibration lever [0086] G.sub.1 Lever gravity centre including the loaded calibration weight [0087] H Horizontal line