Weighing sensor access detection system and detection method of weighing instrument

Abstract

The embodiment of the present invention discloses a weighing sensor access detection system and detection method of a weighing instrument, the system includes an instrument connector, a weighing instrument, and a weighing sensor access detection circuit, the access detection circuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, and a fifth resistor, one end of the first resistor and the fourth resistor are respectively connected to the negative pole and the positive pole of the excitation power supply output terminal, the other end of the first resistor and the fourth resistor are respectively connected to the positive pole and the negative pole of the sensor signal input terminal through the second resistor and the fifth resistor; the two ends of the third resistor are respectively connected to the first resistor and the fourth resistor. The present invention only adds 5 resistors, so that the weighing instrument can quickly detect the connection status of the weighing sensor and respond when plugging and unplugging the weighing sensor through a low-cost simple circuit, and does not affect the metering accuracy and high and low temperature metering performance of the weighing instrument. The function of the present invention is cost-effective and has a wide range of applications.

Description

Technical Field

[0001] The invention relates to the field of weighing instruments, and in particular to a weighing sensor access detection system of a weighing instrument and a detection method thereof. Background Art

[0002] At present, the internal circuit schematic diagram of the commonly used weighing sensor on the market is as follows Figure 1 As shown. The sensitivity of this type of weighing sensor is usually 1mV / V~3mV / V. Under the condition of 5V excitation power supply, the voltage range of the weighing sensor output signal is ±5mV~±15mV. When the user is debugging the weighing system, when the weighing sensor interface is connected to the weighing instrument for live plugging and unplugging, the AD filter circuit at the sensor input end of the weighing instrument cannot be discharged quickly because the filter circuit structure inside the weighing instrument has a series of resistors and capacitors. Therefore, when the weighing sensor interface is plugged and unplugged, the AD filter circuit at the sensor input end of the weighing instrument cannot be discharged quickly, resulting in large fluctuations in the voltage value of the identified sensor input signal, causing the weight display value of the weighing instrument to jump randomly. The weighing instrument cannot quickly and accurately identify the connection status of the weighing sensor, so that the user cannot intuitively observe the plug-in and unplug changes of the sensor interface. When the weighing instrument displays abnormal weight, the user cannot determine whether it is a fault in the installation and connection of the weighing sensor or a fault in the weighing instrument itself, which increases the difficulty for users to troubleshoot weighing display problems at the installation and debugging site. Summary of the invention

[0003] The technical problem to be solved by the embodiments of the present invention is to provide a weighing sensor access detection system and a detection method for a weighing instrument, so as to quickly detect whether the weighing sensor is normally connected.

[0004] In order to solve the above technical problems, an embodiment of the present invention proposes a weighing sensor access detection system for a weighing instrument, including an instrument connector for connecting a weighing sensor and a weighing instrument electrically connected to the instrument connector, wherein the instrument connector includes a positive electrode of a sensor signal input terminal, a negative electrode of a sensor signal input terminal, a positive electrode of an excitation power supply output terminal, and a negative electrode of an excitation power supply output terminal. The system also includes a weighing sensor access detection circuit, wherein the access detection circuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, and a fifth resistor, wherein one end of the first resistor is connected to the negative electrode of the excitation power supply output terminal, and the other end of the first resistor is connected to the positive electrode of the sensor signal input terminal through the second resistor; one end of the fourth resistor is connected to the positive electrode of the excitation power supply output terminal, and the other end is connected to the negative electrode of the sensor signal input terminal through the fifth resistor; two ends of the third resistor are respectively connected to the other end of the first resistor and the other end of the fourth resistor; the resistance values ​​of the first resistor and the fourth resistor differ by less than 20%, and the second resistor and the fifth resistor are high-resistance resistors.

[0005] Furthermore, the weighing instrument detects the voltage difference between the positive electrode of the sensor signal input terminal and the negative electrode of the sensor signal input terminal. When the voltage difference exceeds a preset range, it is determined that the weighing sensor is not connected normally, otherwise it is connected normally.

[0006] Furthermore, when the absolute value of the voltage difference is greater than the output voltage of the excitation power supply of the weighing instrument multiplied by the sensitivity of the weighing sensor, it is determined that the weighing sensor is not connected normally, otherwise it is connected normally.

[0007] Furthermore, the resistance values ​​of the first resistor, the third resistor, and the fourth resistor satisfy the following formula:

[0008] ;

[0009] Wherein, R1, R3, R4 are the resistance values ​​of the first resistor, the third resistor, and the fourth resistor respectively, and S is the sensitivity value of the weighing sensor.

[0010] Furthermore, the resistance value of the third resistor satisfies: 100KΩ≥R3≥1KΩ.

[0011] Furthermore, the resistance value R1 of the first resistor satisfies: 1MΩ≥R1≥10KΩ.

[0012] Furthermore, the weighing instrument includes a control unit, an external communication interface unit, a display unit, an input / output unit, a weight signal processing unit, and an A / D filtering circuit. The control unit is electrically connected to the external communication interface unit, the display unit, the input / output unit, and the weight signal processing unit. The weight signal processing unit is electrically connected to the A / D filtering circuit, and the A / D filtering circuit is electrically connected to the instrument connector.

[0013] Furthermore, the A / D filter circuit is composed of a signal filter circuit and an excitation filter circuit.

[0014] Furthermore, the weighing sensor is composed of a bridge circuit composed of multiple strain gauges.

[0015] Correspondingly, an embodiment of the present invention also provides a detection method for a weighing sensor access detection system of a weighing instrument, including: detecting whether the voltage difference between the positive pole of the sensor signal input terminal and the negative pole of the sensor signal input terminal exceeds a preset range; if so, it is determined that the weighing sensor is not normally connected, otherwise it is normally connected.

[0016] The beneficial effects of the present invention are as follows: the present invention only adds 5 resistors, so that the weighing instrument can quickly detect the connection status of the weighing sensor and respond when plugging and unplugging the weighing sensor only through a low-cost simple circuit, and does not affect the metering accuracy and high and low temperature metering performance of the weighing instrument, and is suitable for fast automatic detection of the access status of the weighing sensor and fault alarm purposes; the function of the present invention is cost-effective and has a wide range of applications; when the data of the weighing system is abnormal, the user can quickly and effectively determine whether it is a fault in the installation and connection of the weighing sensor or a fault in the weighing instrument itself through the detection alarm information of the weighing instrument, thereby effectively reducing the difficulty of users in troubleshooting problems at the installation and debugging site of the weighing system. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is the circuit diagram of the existing weighing sensor.

[0018] Figure 2 The invention discloses a circuit block diagram of a weighing sensor of a weighing instrument according to an embodiment of the present invention connected to a detection system.

[0019] Figure 3 The invention discloses a principle block diagram of a weighing sensor access detection system of a weighing instrument according to an embodiment of the present invention. DETAILED DESCRIPTION

[0020] It should be noted that, in the absence of conflict, the embodiments in the present application and the features in the embodiments may be combined with each other. The present invention is further described in detail below in conjunction with the drawings and specific embodiments.

[0021] In the embodiments of the present invention, if there are directional indications (such as up, down, left, right, front, back, etc.), they are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0022] In addition, in the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features.

[0023] Please refer to Figure 2-3 The weighing sensor access detection system of the weighing instrument of the embodiment of the present invention includes a weighing sensor access detection circuit, an instrument connector and a weighing instrument.

[0024] The instrument connector is used to connect with the weighing sensor. The structures of the weighing instrument and the instrument connector are both existing structures. The instrument connector corresponds to the sensor connector of the weighing sensor, and the instrument connector includes a positive electrode of the sensor signal input terminal, a negative electrode of the sensor signal input terminal, a positive electrode of the excitation power output terminal, and a negative electrode of the excitation power output terminal.

[0025] The weighing instrument includes a control unit, an external communication interface unit, a display unit, an input / output unit, a weight signal processing unit, and an A / D filter circuit. The control unit is electrically connected to the external communication interface unit, the display unit, the input / output unit, and the weight signal processing unit for data processing and interaction. The weight signal processing unit is electrically connected to the A / D filter circuit, and the A / D filter circuit is electrically connected to the instrument connector. The main power supply of the weighing instrument is supplied by an external DC 24V or AC 110V / 220V. The power supply processing part inside the weighing instrument converts the power supply voltage into 5V and 3.3V and supplies it to the main circuit unit of the weighing instrument. The control unit is composed of a single-chip microcomputer or a high-performance MCU.

[0026] The analog voltage signal of the weighing sensor is input to the weighing instrument through the instrument connector, and then passes through the weighing sensor access detection circuit and A / D filter circuit, and then is input to the control unit after A / D conversion and secondary hardware filtering by the weight signal processing unit. The A / D filter circuit consists of a sensor signal (SIG) filter circuit and an excitation (EX) filter circuit. After the control unit performs digital filtering, weight calculation and communication, and display data processing, it outputs the relevant data to the display unit to display the weight information, outputs it to the external communication interface unit for data interaction and management of external industrial equipment, and interacts with the input and output unit to operate the weight-related industrial control process.

[0027] The detection circuit for the weighing sensor includes a first resistor, a second resistor, a third resistor, a fourth resistor, and a fifth resistor. One end of the first resistor is connected to the negative pole of the excitation power supply output terminal, and the other end of the first resistor is connected to the positive pole of the sensor signal input terminal through the second resistor; one end of the fourth resistor is connected to the positive pole of the excitation power supply output terminal, and the other end is connected to the negative pole of the sensor signal input terminal through the fifth resistor; the two ends of the third resistor are respectively connected to the other end of the first resistor and the other end of the fourth resistor. The resistance values ​​of the first resistor and the fourth resistor are the same or close (with an allowable deviation of less than 20%). The resistance values ​​of the second resistor and the fifth resistor are ≥ 10 times the resistance value of the first resistor, that is, the second resistor and the fifth resistor can be high resistance resistors, usually above 1MΩ.

[0028] As an implementation method, the weighing meter detects the voltage difference between the positive electrode of the sensor signal input terminal and the negative electrode of the sensor signal input terminal. When the voltage difference exceeds a preset range (the range is determined by the resistance values ​​of the first resistor, the third resistor, and the fourth resistor), it is determined that the weighing sensor is not connected normally (abnormal connection includes situations where the sensor line is not connected, the access line is abnormal, such as poor contact of the connector position or internal breakage of the sensor connecting line, etc. The following expressions are all defined according to this range), otherwise it is normally connected.

[0029] As an implementation mode, when the absolute value of the voltage difference is greater than the excitation power supply output voltage of the weighing instrument multiplied by the sensitivity of the weighing sensor, it is determined that the weighing sensor is not connected normally, otherwise it is connected normally.

[0030] As an implementation manner, the resistance values ​​of the first resistor, the third resistor, and the fourth resistor satisfy the following formula:

[0031] ;

[0032] Wherein, R1, R3, and R4 are the resistance values ​​of the first resistor, the third resistor, and the fourth resistor respectively, and S is the sensitivity value of the weighing sensor. For example, when the sensitivity of the weighing sensor is 3mV / V, S=3.

[0033] As an implementation method, the resistance value of the third resistor needs to satisfy: 100KΩ≥R3≥1KΩ. Preferably, 10R3=R1.

[0034] As an implementation manner, the resistance value of the first resistor needs to satisfy: 1MΩ≥R1≥10KΩ, preferably 10KΩ.

[0035] As an implementation method, the weighing sensor is composed of a bridge circuit composed of multiple strain gauges. Figure 3 As shown in the figure, R6, R7, R8, and R9 inside the weighing sensor are strain gauge impedances, usually 350Ω to 1000Ω, and together form a bridge circuit. The sensor excitation power supply is (EX-) and (EX+), which are usually 5V to 15V depending on the characteristics of different sensors. The sensor output signal terminals are (SIG+) and (SIG-), and their sensitivity is usually 1mV / V to 3mV / V.

[0036] Embodiment: For example, the resistance values ​​of the first resistor, the second resistor, the third resistor, the fourth resistor, and the fifth resistor are 10KΩ, 10MΩ, 1KΩ, 10KΩ, and 10MΩ, respectively. By using the circuit structure of the present invention, other different resistance values ​​can be used to achieve the same effect.

[0037] When the weighing instrument is not connected to the sensor interface cable, the voltages at both ends of the weighing instrument's excitation power output terminals (EX+) and (EX-) are 5V and 0V (taking the 5V weighing sensor power supply as an example, there are also 10V to 15V weighing sensor power supply systems on the market). Use three resistors, R1 (10KΩ), R3 (1KΩ), and R4 (10KΩ), to divide the voltage, so that when the weighing instrument is unloaded (i.e., the sensor is not normally connected), the voltage at the sensor signal input terminal (SIG+) is 2.38V.

[0038] The voltage at the (SIG-) terminal is 2.62V, and the voltage difference between the (SIG+) terminal and the (SIG-) terminal is -240mV. The calculation method is as follows:

[0039] ;

[0040] ;

[0041] .

[0042] When the weighing instrument provides 5V excitation power to the weighing sensor, the maximum signal voltage that the weighing sensor with a sensitivity of 1mV / V to 3mV / V can output The range is ±5mV~±15mV.

[0043] Take a sensor with a sensitivity of 3mV / V as an example. 3mV / V=15mV, where U is the output voltage of the excitation power supply and S is the sensitivity of the weighing sensor.

[0044] when or , it can be determined that the weighing sensor is not connected normally.

[0045] Since most weighing sensors on the market use unidirectional force detection, the output signal voltage is near the zero zone to the positive range (for example, the range of -0.5mV to 15mV), therefore, the weighing sensor access detection circuit of the present invention configures the signal voltage when the weighing sensor is unloaded (i.e., the sensor is not normally connected) to a large negative voltage (-240mV), so that the weighing meter can more easily detect the abnormality of the weighing sensor connection. In addition, when the weighing sensor is not connected (i.e., the weighing sensor is unloaded), the voltage value (-240mV) collected by the signal input terminal (SIG+) and (SIG-) of the weighing meter is far beyond the signal voltage range of the normal weighing sensor output (for example, the range of -0.5mV to 15mV), so that the meter can further determine the abnormal situation that the weighing sensor is not normally connected.

[0046] When the weighing instrument is normally connected to the weighing sensor interface cable, since the two 10MΩ resistors R2 and R5 are connected to the input loop, the circuit loop is in a high-impedance state, the weighing instrument can still work normally, and the measurement accuracy and high and low temperature measurement performance are not affected.

[0047] According to the above principle, the voltage of the sensor signal input terminal (SIG+) of the weighing instrument is U SIG+ , the voltage of (SIG-) is U SIG- , the differential signal voltage is U SIG , the voltage values ​​of the sensor excitation power supply terminals (EX+) and (EX-) correspond to U EX+ and U EX- , then the corresponding formulas for each voltage parameter are:

[0048] ;

[0049] when When , it can be judged that the weighing sensor is not connected normally. Wherein, U is the voltage at the output end of the excitation power supply, and S is the sensitivity of the weighing sensor.

[0050] When the load cell excitation power supply is 5V and the load cell sensitivity is 3mV / V, theoretically, U SIG =-240mV, the weighing instrument only needs to detect U SIG >15mV or U SIG When the voltage is <-15mV, it can quickly identify whether the sensor interface cable is properly inserted.

[0051] The detection method of the weighing sensor access detection system of the weighing instrument of the embodiment of the present invention includes the following steps: detecting whether the voltage difference between the positive pole of the sensor signal input terminal and the negative pole of the sensor signal input terminal exceeds a preset range; if so, it is judged that the weighing sensor is not normally connected, otherwise it is normally connected.

[0052] The present invention adopts a circuit structure in which five resistors are set at the sensor signal input end of the weighing instrument. When the weighing sensor interface is inserted into the instrument, the weighing instrument can normally perform weight signal sampling, signal filtering and subsequent weight processing. When the weighing sensor interface is unplugged, the weighing sensor access detection circuit of the present invention can quickly provide the A / D filter circuit with a voltage signal value far exceeding the range relative to the normal weighing sensor signal, so that the weighing instrument can quickly identify whether the sensor interface is unplugged, and the circuit does not affect the weighing instrument's measurement accuracy and high and low temperature measurement performance.

[0053] While the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that many changes, modifications, substitutions and variations can be made to the embodiments without departing from the principles and spirit of the invention.

Claims

1. A weighing sensor access detection system for a weighing instrument, comprising an instrument connector for connecting a weighing sensor and a weighing instrument electrically connected to the instrument connector, wherein the instrument connector comprises a positive electrode of a sensor signal input terminal, a negative electrode of a sensor signal input terminal, a positive electrode of an excitation power supply output terminal, and a negative electrode of an excitation power supply output terminal, characterized in that: The system also includes a weighing sensor access detection circuit, which includes a first resistor, a second resistor, a third resistor, a fourth resistor, and a fifth resistor. One end of the first resistor is connected to the negative pole of the excitation power supply output terminal, and the other end of the first resistor is connected to the positive pole of the sensor signal input terminal through the second resistor; one end of the fourth resistor is connected to the positive pole of the excitation power supply output terminal, and the other end is connected to the negative pole of the sensor signal input terminal through the fifth resistor; two ends of the third resistor are respectively connected to the other end of the first resistor and the other end of the fourth resistor; the resistance values ​​of the first resistor and the fourth resistor differ by less than 20%, the second resistor and the fifth resistor are high-resistance resistors, and the high-resistance resistors are resistors of 1MΩ or more; The weighing instrument detects the voltage difference between the positive electrode of the sensor signal input terminal and the negative electrode of the sensor signal input terminal. When the voltage difference exceeds the preset range, that is, when the absolute value of the voltage difference is greater than the output voltage of the excitation power supply of the weighing instrument multiplied by the sensitivity of the weighing sensor, it is judged that the weighing sensor is not connected normally, otherwise it is connected normally; The resistance values ​​of the first resistor, the third resistor, and the fourth resistor satisfy the following formula: ； Wherein, R1, R3, R4 are the resistance values ​​of the first resistor, the third resistor, and the fourth resistor respectively, and S is the sensitivity value of the weighing sensor.

2. The weighing sensor access detection system of the weighing instrument according to claim 1, characterized in that: The resistance value of the third resistor satisfies: 100KΩ≥R3≥1KΩ.

3. The weighing sensor access detection system of the weighing instrument as claimed in claim 1, characterized in that: The resistance value R1 of the first resistor satisfies: 1MΩ≥R1≥10KΩ.

4. The weighing sensor access detection system of the weighing instrument according to claim 1, characterized in that: The weighing instrument includes a control unit, an external communication interface unit, a display unit, an input / output unit, a weight signal processing unit, and an A / D filtering circuit. The control unit is electrically connected to the external communication interface unit, the display unit, the input / output unit, and the weight signal processing unit. The weight signal processing unit is electrically connected to the A / D filtering circuit, and the A / D filtering circuit is electrically connected to the instrument connector.

5. The weighing sensor access detection system of the weighing instrument as claimed in claim 4, characterized in that: The A / D filter circuit consists of a signal filter circuit and an excitation filter circuit.

6. The weighing sensor access detection system of a weighing instrument as claimed in claim 1, characterized in that: The weighing sensor is composed of a bridge circuit composed of a plurality of strain gauges.

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