CN220153731U - Sensor access detection unit based on weighing instrument - Google Patents
Sensor access detection unit based on weighing instrument Download PDFInfo
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- CN220153731U CN220153731U CN202322848862.7U CN202322848862U CN220153731U CN 220153731 U CN220153731 U CN 220153731U CN 202322848862 U CN202322848862 U CN 202322848862U CN 220153731 U CN220153731 U CN 220153731U
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- 238000001514 detection method Methods 0.000 title claims abstract description 30
- 238000005303 weighing Methods 0.000 title claims abstract description 22
- 230000005284 excitation Effects 0.000 claims abstract description 22
- 230000000087 stabilizing effect Effects 0.000 claims abstract description 15
- 238000012544 monitoring process Methods 0.000 abstract description 2
- 239000003990 capacitor Substances 0.000 description 6
- 238000010586 diagram Methods 0.000 description 6
- 230000003321 amplification Effects 0.000 description 2
- 238000003199 nucleic acid amplification method Methods 0.000 description 2
- 230000004075 alteration Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
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Abstract
The embodiment of the utility model discloses a sensor access detection unit based on a weighing instrument, which comprises an MCU, a sensor interface, an excitation source voltage stabilizing circuit and a power supply end, wherein the output end of the excitation source voltage stabilizing circuit is connected with the sensor interface, the detection unit comprises a current detection circuit and a follower circuit, the current detection circuit comprises a current detection resistor and a current amplifier, the positive electrode and the negative electrode of the input end of the current amplifier are respectively connected with the power supply end and the input end of the excitation source voltage stabilizing circuit, the output end of the current amplifier is connected with the follower circuit, the output end of the follower circuit is connected with the port of an analog-to-digital converter of the MCU, and the two ends of the current detection resistor are respectively connected with the positive electrode and the negative electrode of the input end of the current amplifier. The utility model determines whether the sensor is connected or not by monitoring the exciting current of the sensor interface of the weighing instrument, has high response speed, does not influence the weighing precision and the high-low temperature linearity, and is stable and reliable.
Description
Technical Field
The utility model relates to the technical field of weighing meters, in particular to a sensor access detection unit based on a weighing meter.
Background
In field applications of weighing meters, when a sensor is not connected or disconnected, the common mode capacitance and the differential mode capacitance are measured between the positive and negative signals of the sensor interface of the meter, and because the capacitance discharges slowly, the weight value is often changed from large to small, or from small to large, or a random value is kept unchanged, which often causes a field staff to misunderstand that the sensor is connected.
The traditional solution is to add a pull-down resistor to the signal positive or add a pull-up resistor to the signal negative, so as to accelerate the charge and discharge of the capacitor. According to the method, if the resistor with a large resistance value is selected, the influence on the weighing precision is small, but the solving effect is not obvious, and if the resistor with a small resistance value (for example, 10M) is selected, the weighing precision and the high-low temperature linearity of the instrument are influenced. The reasons for affecting accuracy and linearity are as follows:
FIG. 1 is an internal circuit diagram of a sensor, V EXCITATION+ And V EXCITATION– Is the power supply of the sensor, V SIGNAL+ And V SIGNAL– Differential signal output of sensor when signal is positive V SIGNAL+ Sum signal negative V SIGNAL– The pull-down and pull-up resistors are equivalent to the parallel resistors of R1 and R4 in FIG. 1, which affects the accuracy of the bridge itself. The temperature drift problem of the pull-up resistor and the pull-down resistor is solved, so that the linearity of high and low temperatures is responded.
Disclosure of Invention
The technical problem to be solved by the embodiment of the utility model is to provide a sensor access detection unit based on a weighing instrument so as to detect whether a sensor is accessed or not, and meanwhile, the accuracy and the linearity of measurement are not affected.
In order to solve the technical problems, the embodiment of the utility model provides a sensor access detection unit based on a weighing instrument, the weighing instrument comprises an MCU, a sensor interface, an excitation source voltage stabilizing circuit and a power supply end, the output end of the excitation source voltage stabilizing circuit is connected with the sensor interface, the detection unit comprises a current detection circuit and a follower circuit, the current detection circuit comprises a current detection resistor and a current amplifier, the positive electrode and the negative electrode of the input end of the current amplifier are respectively connected with the power supply end and the input end of the excitation source voltage stabilizing circuit, the output end of the current amplifier is connected with the follower circuit, the output end of the follower circuit is connected with an analog-to-digital converter port of the MCU, and the two ends of the current detection resistor are respectively connected with the positive electrode and the negative electrode of the input end of the current amplifier.
Furthermore, the excitation source voltage stabilizing circuit adopts an LDO chip, the input end of the LDO chip is connected with the negative electrode of the input end of the current amplifier, and the output end of the LDO chip is connected with the positive pressure excitation output pin of the sensor interface.
Further, the LDO chip is an LDO chip converting 6V to 5V output.
Further, the follower circuit adopts a current follower, and the input end and the output end of the current follower are respectively connected with the output end of the current amplifier and the analog-to-digital converter port of the MCU through an RC filter circuit.
The beneficial effects of the utility model are as follows: the utility model determines whether the sensor is connected or not by monitoring the exciting current of the sensor interface of the weighing instrument, has high response speed, does not influence the weighing precision and the high-low temperature linearity, and is stable and reliable.
Drawings
Fig. 1 is a diagram showing an internal circuit configuration of a conventional sensor.
FIG. 2 is a circuit diagram of a sensor interface according to an embodiment of the present utility model.
FIG. 3 is a circuit diagram of an excitation source voltage stabilizing circuit according to an embodiment of the present utility model.
Fig. 4 is a circuit diagram of a current detection circuit according to an embodiment of the present utility model.
Fig. 5 is a circuit diagram of a follower circuit of an embodiment of the present utility model.
Detailed Description
It should be noted that, without conflict, the embodiments of the present utility model and features of the embodiments may be combined with each other, and the present utility model will be further described in detail with reference to the drawings and the specific embodiments.
In the embodiment of the present utility model, if there is a directional indication (such as up, down, left, right, front, and rear … …) only for explaining the relative positional relationship, movement condition, etc. between the components in a specific posture (as shown in the drawings), if the specific posture is changed, the directional indication is correspondingly changed.
In addition, the description of "first," "second," etc. in this disclosure is for descriptive purposes only and is not to be construed as indicating or implying a relative importance or implying an indication of the number of features being indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature.
The weighing instrument comprises an MCU, a sensor interface, an excitation source voltage stabilizing circuit and a power supply end. This part belongs to the prior art. The power supply end of the power supply provides 6V voltage, the sensor interface is shown as J1 in FIG. 2, wherein the 1 pin is the positive pressure excitation output 5V of the sensor, the 2 pin is the negative pressure excitation output 0V of the sensor, and the 3 and 4 pins are the differential signal inputs of the sensor. The output end of the excitation source voltage stabilizing circuit is connected with the sensor interface, and the 6V voltage of the power supply end is converted into 5V to supply power to the sensor interface, so that the sensor is powered.
Referring to fig. 2 to 5, a sensor access detection unit based on a weighing instrument according to an embodiment of the present utility model includes a current detection circuit and a follower circuit.
The current detection circuit includes a current detection resistor and a current amplifier. The positive and negative poles of the input end of the current amplifier are respectively connected with the power supply end and the input end of the excitation source voltage stabilizing circuit, the output end of the current amplifier is connected with the follower circuit, the output end of the follower circuit is connected with the analog-digital converter port of the MCU, and the two ends of the current detection resistor are respectively connected with the positive and negative poles of the input end of the current amplifier. As shown in fig. 4, the resistor R1 is a current detection resistor, U2 is a current amplifier, and the amplification factor is 50V/V. Resistor R1 is not placed at the back end of the LDO for detection mainly because the voltage accuracy of the excitation source is affected. The power consumption of the LDO is negligible in microampere level, so the detection resistor is placed in the front stage of the LDO.
When the weighing instrument is connected with a 350 omega sensor, the current is 14.3mA. The voltage across resistor R1 is 7.15mV, and the output voltage of the 6 pins of the current amplifier is 0.358V because the amplification factor of the current amplifier is 50V/V, and is 2.86V if 8 sensors are connected. If no sensor is connected, the voltage of the resistor R1 is zero, and the voltage output of the 6 pin of the current amplifier is zero.
As one implementation mode, the excitation source voltage stabilizing circuit adopts an LDO chip (shown in FIG. 3, U1 is a high-precision low-noise LDO), the input end of the LDO chip is connected with the input end cathode of the current amplifier, and the output end of the LDO chip is connected with the positive pressure excitation output pin of the sensor interface. The LDO chip is an LDO chip for converting 6V into 5V output. The output end of the LDO chip is connected with a plurality of capacitors (such as a capacitor C2, a capacitor C3, a capacitor C4 and a capacitor C5 in FIG. 3).
As an implementation mode, the follower circuit adopts a current follower, and an input end and an output end of the current follower are respectively connected with an output end of the current amplifier and an analog-to-digital converter port of the MCU through an RC filter circuit. As shown in fig. 5, R4 and C11 constitute an input filter, and R3 and C10 constitute an output filter. The output end is connected to the port of the analog-digital converter of the MCU, and the magnitude of the current value is calculated.
Therefore, when a sensor is accessed, the ADC port of the singlechip can detect a voltage value. When no sensor is connected, the voltage value detected by the ADC port of the singlechip is zero. Meanwhile, the current detection resistor is arranged at the front end of LDO voltage stabilization, so that the output voltage of the LDO is not influenced, and the weighing result is not influenced.
Although embodiments of the present utility model have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the spirit and scope of the utility model as defined by the appended claims and their equivalents.
Claims (4)
1. The sensor access detection unit based on the weighing instrument comprises an MCU, a sensor interface, an excitation source voltage stabilizing circuit and a power supply end, wherein the output end of the excitation source voltage stabilizing circuit is connected with the sensor interface.
2. The sensor access detection unit based on the weighing instrument according to claim 1, wherein the excitation source voltage stabilizing circuit adopts an LDO chip, the input end of the LDO chip is connected with the input end cathode of the current amplifier, and the output end of the LDO chip is connected with the positive pressure excitation output pin of the sensor interface.
3. The weighing-meter-based sensor access detection unit of claim 2, wherein the LDO chip is a 6V to 5V output LDO chip.
4. The sensor access detection unit based on the weighing instrument according to claim 1, wherein the follower circuit adopts a current follower, and an input end and an output end of the current follower are respectively connected with an output end of the current amplifier and an analog-to-digital converter port of the MCU through an RC filter circuit.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202322848862.7U CN220153731U (en) | 2023-10-24 | 2023-10-24 | Sensor access detection unit based on weighing instrument |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202322848862.7U CN220153731U (en) | 2023-10-24 | 2023-10-24 | Sensor access detection unit based on weighing instrument |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN220153731U true CN220153731U (en) | 2023-12-08 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202322848862.7U Active CN220153731U (en) | 2023-10-24 | 2023-10-24 | Sensor access detection unit based on weighing instrument |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN220153731U (en) |
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2023
- 2023-10-24 CN CN202322848862.7U patent/CN220153731U/en active Active
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