A weighing force sensor using a star bridge

Abstract

The present invention belongs to the field of sensor circuit technology and provides a weighing force sensor using a star bridge, comprising: a first circuit, a second circuit, a third circuit, and a fourth circuit; each of the first circuit, the second circuit, the third circuit, and the fourth circuit is provided with a measuring element, and one end of each of the first circuit, the second circuit, the third circuit, and the fourth circuit is grounded; the other ungrounded end of the first circuit is connected to one end of a first signal, and the other ungrounded end of the fourth circuit is connected to the other end of the first signal, with a potential difference between the two ends of the first signal; the other ungrounded end of the second circuit is connected to one end of a second signal, and the other ungrounded end of the third circuit is connected to the other end of the second signal, with a potential difference between the two ends of the second signal. The present invention reduces the drift problem of the strain gauge measurement bridge and improves the EMC interference immunity of the input end, thereby ensuring the accuracy and stability of the sensor.

Description

Technical Field

[0001] The invention belongs to the technical field of sensor circuits, and in particular relates to a weighing force sensor using a star bridge. Background Art

[0002] Resistive strain sensors use a strain gauge and an elastic element as conversion elements, converting force into a voltage signal via a Wheatstone bridge. These sensors are widely used in the field of weighing and force measurement due to their high accuracy, wide measurement range, long life, and simple structure. However, their stability and reliability are often affected by the sensor structure, elastic element material, strain gauge characteristics, manufacturing process, ambient temperature, and the bridge circuit.

[0003] The Wheatstone bridge used in today's load cell will bring the following problems: In the traditional circuit design of the load cell using the Wheatstone bridge, whether it is constant voltage excitation or constant current excitation, such as Figure 1 As shown, if the strain gauge G1 and the strain gauge G3 are both in an environment of a first electric field strength, and the strain gauge G2 and the strain gauge G4 are both in an environment of a second electric field strength, and the first electric field strength and the second electric field strength are different; then the relative strain gauges G1 and strain gauges G3, as well as the relative strain gauges G2 and strain gauges G4 are under a higher voltage, the test resistance values ​​tested by the resistors corresponding to each strain gauge will deviate more than the actual resistance values, thereby causing the measurement accuracy and measurement stability of the entire weighing force sensor to deteriorate.

[0004] Existing technologies primarily improve sensor stability and reliability by optimizing sensor structure, component materials, and manufacturing processes, as well as implementing temperature compensation. However, as the use of weighing and force measurement equipment expands and the demand for measurement accuracy increases, the requirements for sensor stability and reliability are also increasing accordingly. In some applications, weighing equipment may not be able to operate efficiently due to issues such as sensor stability and reliability.

[0005] In view of this, those skilled in the art have developed a weighing force sensor using a star-shaped bridge and internal strain gauges with equal electric field intensity distribution, in order to overcome the above problems. Summary of the Invention

[0006] The technical problem to be solved by the present invention is that when the existing weighing force sensor directly adopts the Wheatstone bridge and faces an unevenly distributed electric field environment, the overall measurement accuracy decreases.

[0007] The technical solution adopted by the present invention to solve the technical problem is: providing a weighing force sensor using a star-shaped bridge.

[0008] A weighing force sensor using a star bridge comprises: a first circuit, a second circuit, a third circuit, and a fourth circuit; the first circuit, the second circuit, the third circuit, and the fourth circuit are all provided with a measuring element, and one end of the first circuit, the second circuit, the third circuit, and the fourth circuit are all grounded;

[0009] The other ungrounded end of the first circuit is connected to one end of the first signal, the other ungrounded end of the fourth circuit is connected to the other end of the first signal, and there is a potential difference between the two ends of the first signal; the other ungrounded end of the second circuit is connected to one end of the second signal, and the other ungrounded end of the third circuit is connected to the other end of the second signal, and there is a potential difference between the two ends of the second signal.

[0010] Furthermore, the ground terminal of the first circuit, the ground terminal of the second circuit, the ground terminal of the third circuit and the ground terminal of the fourth circuit are connected to the same ground port.

[0011] Furthermore, the ground end of the first circuit and the ground end of the fourth circuit are connected to the same first ground port, the ground end of the second circuit and the ground end of the third circuit are connected to the same second ground port, both the first ground port and the second ground port are grounded through wires, and the first ground port and the second ground port are different ports.

[0012] Furthermore, the sensor also includes an elastic element, the measuring element in the first circuit and the measuring element in the fourth circuit are located in the compressive strain zone of the elastic element, and the measuring element in the second circuit and the measuring element in the third circuit are located in the tensile strain zone of the elastic element.

[0013] Furthermore, the sensor also includes an elastic base, a measuring cavity is provided on one side of the base, and a PCB board is provided on the other side of the base; a load-bearing part is provided on the top of the base close to the measuring cavity, and a fixing part is provided on the top of the base close to the PCB board; the measuring part is a strain gauge, and the strain gauge is distributed in the measuring cavity.

[0014] Furthermore, the strain gauges are evenly and symmetrically distributed in the measuring cavity in the circumferential direction.

[0015] Furthermore, the first signal and the second signal are constant current excitations.

[0016] Furthermore, the measuring element includes a strain gauge and / or a resistor, each measuring element includes at least one strain gauge or resistor, and at least one measuring element includes a strain gauge.

[0017] Furthermore, the first signal and the second signal are input and output in parallel.

[0018] Furthermore, the weighing force sensor calculates the gravity output value through the strain gauge resistance, the preset strain coefficient and the preset proportional coefficient; the strain coefficient is the ratio between the strain gauge resistance and the strain degree, and the proportional coefficient is the ratio between the strain degree and the gravity output value, and the proportional coefficient and the strain coefficient are both preset values.

[0019] The beneficial effects of the present invention are as follows: the present invention utilizes a star circuit to achieve dual-channel output of a first signal and a second signal. When one circuit is affected, the other circuit can operate normally, thereby ensuring the stability of the operation of the load-bearing force sensor of the entire star bridge. At the same time, during operation, the common end of the first circuit, the second circuit, the third circuit, and the fourth circuit in the star circuit is directly or indirectly grounded, and the circuit preferentially uses constant current excitation instead of the original constant voltage excitation. This solves the problem of instability of the weighing sensor caused by the strain gauge under different electric field strengths and the larger deviation of the measured resistance value of the strain gauge under high voltage compared to the actual resistance value in the traditional design. This reduces the drift problem of the strain gauge measurement bridge and improves the EMC interference immunity of the input end, thereby ensuring the accuracy and stability of the sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without inventive work. The present invention will now be described in detail with reference to the drawings. This figure is a simplified schematic diagram that only illustrates the basic structure of the present invention in a schematic manner. Therefore, it only shows the components related to the present invention.

[0021] Figure 1 This is a circuit diagram of the weighing force sensor mentioned in the background technology;

[0022] Figure 2 This is a circuit connection diagram of a weighing force sensor using a star bridge;

[0023] Figure 3 This is a circuit connection diagram of a weighing force sensor using a star bridge;

[0024] Figure 4 This is the structural diagram of the weighing force sensor using a star bridge;

[0025] Figure 5 yes Figure 3 Schematic diagram of the electric field intensity distribution between the measuring element and the elastic element in the circuit schematic;

[0026] Figure 6This is a circuit connection diagram of a weighing force sensor using a star bridge;

[0027] Figure 7 yes Figure 6 Schematic diagram of the electric field intensity distribution between the measuring piece and the elastic element in the circuit diagram. DETAILED DESCRIPTION

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0029] The present invention provides a weighing force sensor using a star bridge, such as Figure 2 and Figure 3 As shown, it includes: a first circuit 11, a second circuit 12, a third circuit 13 and a fourth circuit 14. The first circuit 11, the second circuit 12, the third circuit 13 and the fourth circuit 14 are all provided with measuring pieces, which are divided into a first measuring piece G1 located in the first circuit 11, a second measuring piece G2 located in the second circuit 12, a third measuring piece G3 located in the third circuit 13, and a fourth measuring piece G4 located in the fourth circuit.

[0030] One end of the first circuit 11, the second circuit 12, the third circuit 13, and the fourth circuit 14 are all grounded. The ungrounded end of the first circuit 11 is connected to one end of the first signal SIG_1, and the ungrounded end of the fourth circuit 14 is connected to the other end of the first signal SIG_1. The two ends of the first signal SIG_1 are +SIG_1 and -SIG_1, respectively, and a potential difference exists between the two ends of the first signal SIG_1. The ungrounded end of the second circuit 12 is connected to one end of the second signal SIG_2, and the ungrounded end of the third circuit 13 is connected to the other end of the second signal SIG_2. The two ends of the second signal SIG_2 are +SIG_2 and -SIG_2, respectively, and a potential difference exists between the two ends of the second signal SIG_2.

[0031] In an example, one end of the first circuit 11, the second circuit 12, the third circuit 13 and the fourth circuit 14 are all grounded, specifically: Figure 2 As shown, the ground end of the first circuit 11 and the ground end of the fourth circuit 14 are connected to the same first ground port, and the ground end of the second circuit 12 and the ground end of the third circuit 13 are connected to the same second ground port. The first ground port and the second ground port are both grounded through wires, and the first ground port and the second ground port are different ports.

[0032] In an example, one end of the first circuit 11, the second circuit 12, the third circuit 13 and the fourth circuit 14 are all grounded, specifically: Figure 3 As shown, the grounding terminals of the first circuit 11, the second circuit 12, the third circuit 13 and the fourth circuit 14 are connected to the same grounding port (ie, a common port) and are grounded via the grounding port.

[0033] In actual application, the weighing force sensor using a star bridge also includes an elastic element. The measuring piece in the first circuit and the measuring piece in the fourth circuit are located in the compressive strain zone of the elastic element, and the measuring piece in the second circuit and the measuring piece in the third circuit are located in the tensile strain zone of the elastic element.

[0034] In some examples, the measuring elements include strain gauges and / or resistors, with each measuring element including at least one strain gauge or resistor, and at least one measuring element including a strain gauge. In other words, in a load-bearing force sensor, it is not permitted for all measuring elements to be resistors, or for all measuring elements to be composed entirely of multiple resistors.

[0035] Specifically, the measuring piece can be composed of one resistor, or multiple resistors, or one strain gauge, or multiple strain gauges, or a strain gauge and a resistor; and at least one of the first measuring piece G1, the second measuring piece G2, the third measuring piece G3 or the fourth measuring piece G4 includes a strain gauge.

[0036] Specifically, such as Figure 3 As shown, the ground terminals of the first circuit 11, the second circuit 12, the third circuit 13, and the fourth circuit 14 are connected to the same ground port. The first measuring element G1 and the second measuring element G2 are arranged in the compressive strain region of the elastic element, and the third measuring element G3 and the fourth measuring element G4 are arranged in the tensile strain region of the elastic element. The local surface of the first signal and the second signal in the elastic element is shown in FIG. Figure 5 As shown, the negative pole -SIG_1 of the first signal SIG_1 is connected to the left end of the first measuring piece G1, the right end of the first measuring piece G1 is grounded GND, the left end of the second measuring piece G2 is grounded GND, and the right end of the second measuring piece is connected to the positive pole +SIG_2 of the second signal SIG_2 and then grounded GND, wherein the first measuring piece G1 and the second measuring piece G2 are both connected to the surface of the elastic element through adhesive.

[0037] When the corresponding first measuring piece G1, second measuring piece G2, third measuring piece G3 and fourth measuring piece G4 all use a single strain gauge, the electric field distribution corresponding to each strain gauge is as follows: Figure 5As shown, the electric field distributions between different strain gauges correspond to each other. It can be seen that in this circuit, when the strain gauge resistance values ​​are the same, the electric field strength distribution pattern between each strain gauge and the elastic element is the same. Therefore, there is no difference in electric field strength between strain gauges as in a traditional Wheatstone bridge. The weighing force sensor using a star bridge reduces the drift problem of the strain gauge measurement bridge.

[0038] In some examples, such as Figure 6 and Figure 7 As shown, the first and second signals are input and output in parallel. Accordingly, the first and second signals can be combined into a single signal. The non-grounded end of the first circuit 11 and the non-grounded end of the second circuit 12 share a transceiver port, which is connected to the negative terminal of the signal SIG. The non-grounded end of the third circuit 13 and the non-grounded end of the fourth circuit 14 share another transceiver port, which is connected to the positive terminal of the signal SIG.

[0039] Specifically, Figure 6 As shown, the ground terminals of the first circuit 11 and the fourth circuit 14 are connected to the same first ground port, while the ground terminals of the second circuit 12 and the third circuit 13 are connected to the same second ground port. Both the first and second ground ports are grounded via wires, and the first and second ground ports are different ports. The ungrounded terminal of the first circuit 11 is connected to the third signal -SIG terminal, the ungrounded terminal of the fourth circuit 14 is connected to the third signal +SIG terminal, the ungrounded terminal of the second circuit 12 is connected to the third signal -SIG terminal, and the ungrounded terminal of the third circuit 13 is connected to the third signal +SIG terminal. A potential difference exists between the third signal -SIG terminal and the third signal +SIG terminal.

[0040] In practical applications, the first measuring element G1 includes a first strain gauge, the second measuring element G2 includes a second strain gauge, the third measuring element G3 includes a third strain gauge, and the fourth measuring element G4 includes a fourth strain gauge. The first and second strain gauges are attached to the compressive strain region of the elastic element, while the third and fourth strain gauges R3 and R4 are attached to the tensile strain region of the elastic element. Constant current excitation is applied across the - / +SIG terminals, which are the sensor signal output terminals and output differential voltage signals.

[0041] like Figure 7 As shown, when the corresponding first measuring piece G1, second measuring piece G2, third measuring piece G3 and fourth measuring piece G4 all use a single strain gauge, the electric field distribution corresponding to each strain gauge is as follows: Figure 5 As shown, the electric field distributions between different strain gauges correspond to each other.

[0042] like Figure 4As shown, the weighing force sensor also includes an elastic base 1, a measuring cavity 2 is provided on the left side of the base 1, and a PCB board 3 is provided on the right side of the base 1; a load-bearing part 4 is provided on the top of the base 1 close to the measuring cavity 2, and a fixing part 5 is provided on the top of the base 1 close to the PCB board 3; the measuring parts are distributed in the measuring cavity.

[0043] Specifically, the base 1 is an elastic element, which can be rectangular, triangular, circular, or diamond-shaped; the measuring cavity 2 is a through hole set on one side of the base 1, which can be a prototype through hole, a rectangular through hole, or a plum blossom-shaped through hole.

[0044] In some examples, there are four measuring elements, each including a strain gauge. The strain gauges are evenly and symmetrically distributed around the measuring cavity. This distribution allows the strain gauges to fully sense the deformation of the elastic base 1 in response to external weight, ensuring overall accuracy. The strain gauges are preferably arc-shaped and conform to the surface of the measuring cavity 2; specifically, the strain gauges are attached to the inner or outer wall of the measuring cavity using adhesive.

[0045] Specifically, the first and second signals are preferably set as differential signals with constant current excitation. The constant current excitation form improves the ability to resist interference from external non-uniform electric fields. At the same time, the differential signal is preferably selected as a signal with a potential difference between the two ends.

[0046] Furthermore, the first and second strain gauges, respectively attached to the tensile and compressive strain zones of base 1, form the first output (constant current excitation is applied across - / +SIG_1, which serves as the sensor signal output terminal and outputs a differential voltage signal). The third and fourth strain gauges, respectively attached to the tensile and compressive strain zones of base 1, form the second output (constant current excitation is applied across - / +SIG_2, which serves as the sensor signal output terminal and outputs a differential voltage signal). This solution thus achieves dual outputs. That is, even if one circuit is affected, the other circuit can continue to operate normally, ensuring the reliability of the sensor.

[0047] In some examples, such as Figure 4 As shown, the load-bearing part 4 is arranged above the measuring cavity 2. When the weighing force sensor of the star bridge is used, the object to be measured is placed above the load-bearing part 4. The gravity of the object causes the measuring cavity 2, which is a circular through hole, to deform, and at the same time drives the strain gauge adhered to the surface of the measuring cavity 2 to deform, causing the resistance of the strain gauge to change. As a result, the voltage / current at the signal output end of the circuit changes, and is proportional to the magnitude of the applied gravity, and this voltage / current signal is converted into a data signal.

[0048] In some examples, the PCB 3 is a printed circuit board, including an inertial measurement module and a data processing module. When a star-bridge load cell is operating, the PCB 3 operates, and the PCB 3 is connected to an external screen for displaying the final weighing data.

[0049] The PCB board 3 in the weighing force sensor calculates the gravity output value through the strain gauge resistance, the preset strain coefficient and the preset proportional coefficient; the strain coefficient is the ratio between the strain gauge resistance and the strain degree, and the proportional coefficient is the ratio between the strain degree and the gravity output value. Both the proportional coefficient and the strain coefficient are preset values.

[0050] Among them, the strain coefficient is the value measured and calculated by the staff for the weighing force sensor when it is in use. The strain coefficient is directly related to the material used for the strain gauge; the proportional coefficient is the value measured and calculated by the staff for the weighing force sensor before use. The proportional coefficient is directly used to associate with the overall weighing measurement sensor. That is to say, different sensors have different proportional coefficients.

[0051] In some examples, the fixing portion 5 is provided with a plurality of fixing holes so that the load cell using a star bridge can be fixed on the vehicle.

[0052] When using a load cell with a star bridge, the weight of the object to be measured is applied to the load-bearing part 4. The measuring cavity 2 under the load-bearing part 4 deforms under the action of gravity, causing the strain gauges on the inner surface of the measuring cavity 2 to deform, the resistance of the strain gauges to change, and the electric field generated by the circuit to change at the same time. Figure 3 In the circuit shown, the four strain gauges are connected in a star configuration, with the right ends of the first, fourth, second, and third strain gauges all grounded. This ensures that the potentials of the four strain gauges, namely, the right ends of the first, fourth, second, and third strain gauges, are all zero. In this case, the potential differences between the input and output terminals of the first, second, third, and fourth strain gauges are the same, effectively reducing the effects of different potential differences on the strain gauge resistance.

[0053] In addition, the present invention connects the right end of the first strain gauge of the first strain gauge, the right end of the fourth strain gauge, the left end of the second strain gauge, and the left end of the third strain gauge so that the potential difference of each strain gauge is the same during operation, thereby improving the drift of the strain gauge resistance value under high voltage, improving the EMC (electromagnetic compatibility) immunity of the input end, improving the bridge measurement accuracy and stability, and improving the stability within the product life cycle.

[0054] The above is only an embodiment of the present invention. Common knowledge such as the known specific structures and characteristics in the scheme is not described in detail here. Ordinary technicians in the field are aware of all common technical knowledge in the technical field of the invention before the application date or priority date, can obtain all existing technologies in the field, and have the ability to apply conventional experimental means before that date. Ordinary technicians in the field can improve and implement this scheme in combination with their own abilities under the inspiration given by this application. Some typical known structures or known methods should not become obstacles for ordinary technicians in the field to implement this application. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention. These will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

[0055] With the above-described preferred embodiments of the present invention as inspiration, and with reference to the above description, relevant personnel may make various changes and modifications without departing from the scope of the present invention. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A weighing force sensor using a star bridge, characterized in that: include: a first circuit, a second circuit, a third circuit, and a fourth circuit; the first circuit, the second circuit, the third circuit, and the fourth circuit are all provided with a measuring element, and one end of the first circuit, the second circuit, the third circuit, and the fourth circuit are all grounded; The other ungrounded end of the first circuit is connected to one end of the first signal, the other ungrounded end of the fourth circuit is connected to the other end of the first signal, and a potential difference exists between the two ends of the first signal; the other ungrounded end of the second circuit is connected to one end of the second signal, the other ungrounded end of the third circuit is connected to the other end of the second signal, and a potential difference exists between the two ends of the second signal, the first signal and the second signal are constant current excitations, and the first signal and the second signal are input and output in parallel; The sensor also includes an elastic element, the measuring element in the first circuit and the measuring element in the fourth circuit are located in the compressive strain zone of the elastic element, and the measuring element in the second circuit and the measuring element in the third circuit are located in the tensile strain zone of the elastic element; the measuring element includes strain gauges and / or resistors, each measuring element includes at least one strain gauge or resistor, and at least one measuring element includes a strain gauge.

2. The weighing force sensor using a star bridge according to claim 1, characterized in that: The grounding terminal of the first circuit, the grounding terminal of the second circuit, the grounding terminal of the third circuit and the grounding terminal of the fourth circuit are connected to the same grounding port.

3. The weighing force sensor using a star bridge according to claim 1, characterized in that: The grounding end of the first circuit and the grounding end of the fourth circuit are connected to the same first grounding port, the grounding end of the second circuit and the grounding end of the third circuit are connected to the same second grounding port, both the first grounding port and the second grounding port are grounded through wires, and the first grounding port and the second grounding port are different ports.

4. The weighing force sensor using a star bridge according to claim 1, characterized in that: The sensor also includes an elastic base, a measuring cavity is provided on one side of the base, and a PCB board is provided on the other side of the base; a load-bearing part is provided on the top of the base close to the measuring cavity, and a fixing part is provided on the top of the base close to the PCB board; the measuring part is a strain gauge, and the strain gauge is distributed in the measuring cavity.

5. The weighing force sensor using a star bridge according to claim 4, characterized in that: The strain gauges are evenly and symmetrically distributed in the measuring cavity in the circumferential direction.

6. The weighing force sensor using a star bridge according to claim 1, characterized in that: The weighing force sensor calculates the gravity output value through the strain gauge resistance, the preset strain coefficient and the preset proportional coefficient; The strain coefficient is the ratio between the resistance of the strain gauge and the degree of strain, and the proportional coefficient is the ratio between the degree of strain and the gravity output value. Both the proportional coefficient and the strain coefficient are preset values.

Images