阅读说明：本技术 抗温漂称重传感器信号测量电路 (Temperature drift resistant weighing sensor signal measuring circuit ) 是由 许兆欣 金西汉 尚学勇 于 2021-11-08 设计创作，主要内容包括：本发明实施例公开了一种抗温漂称重传感器信号测量电路,包括应变片式称重传感器、MCU、第一信号测量ADC、放大器电路、电源、第二信号测量ADC以及用于分压的电阻R1和电阻R2,第一信号测量ADC的参考电压端通过电阻R1检测应变片式称重传感器的供电电压,电阻R2的两端分别连接第一信号测量ADC参考电压端的两极,第二信号测量ADC与MCU连接通讯,第二信号测量ADC的参考电压端检测应变片式称重传感器的供电电压,第二信号测量ADC的信号检测端连接第一信号测量ADC参考电压端,MCU根据第二信号测量ADC的测量指对被测信号进行修正。本发明既解决了被测信号放大倍数的问题,也解决了分压电路受温度影响导致测量不准的问题。(The embodiment of the invention discloses a temperature drift resistant weighing sensor signal measuring circuit which comprises a strain gauge type weighing sensor, an MCU, a first signal measuring ADC, an amplifier circuit, a power supply, a second signal measuring ADC, a resistor R1 and a resistor R2, wherein the resistor R1 and the resistor R2 are used for voltage division, a reference voltage end of the first signal measuring ADC detects the power supply voltage of the strain gauge type weighing sensor through a resistor R1, two ends of the resistor R2 are respectively connected with two poles of a reference voltage end of the first signal measuring ADC, the second signal measuring ADC is in communication with the MCU, a reference voltage end of the second signal measuring ADC detects the power supply voltage of the strain gauge type weighing sensor, a signal detection end of the second signal measuring ADC is connected with a reference voltage end of the first signal measuring ADC, and the MCU corrects a measured signal according to a measurement finger of the second signal measuring ADC. The invention solves the problem of measured signal amplification factor and the problem of inaccurate measurement caused by the influence of temperature on the voltage division circuit.)

1. A temperature drift resistant weighing sensor signal measuring circuit comprises a strain gauge type weighing sensor, an MCU, a first signal measuring ADC, an amplifier circuit and a power supply, wherein the power supply comprises a 5V output end and a 3.3V output end, 5V output voltage is provided for the strain gauge type weighing sensor, and 3.3V output voltage is provided for the MCU; the first signal measurement ADC is connected with the MCU and the amplifier circuit, the first signal measurement ADC detects a measured signal output by the strain gauge type weighing sensor through the amplifier circuit, the measuring circuit is characterized by further comprising a second signal measurement ADC, a resistor R1 and a resistor R2, the resistor R1 is used for dividing voltage, a reference voltage end of the first signal measurement ADC detects power supply voltage of the strain gauge type weighing sensor, two ends of the resistor R2 are respectively connected with two poles of a reference voltage end of the first signal measurement ADC, the second signal measurement ADC is in communication with the MCU, a reference voltage end of the second signal measurement ADC detects the power supply voltage of the strain gauge type weighing sensor, a signal detection end of the second signal measurement ADC is connected with a reference voltage end of the first signal measurement ADC, the MCU corrects the measured signal according to the change condition of the reference voltage of the first signal measurement ADC measured by the second signal measurement ADC, and calculating to obtain a weight value.

2. The temperature drift resistant load cell signal measurement circuit of claim 1, wherein the MCU calculates the Weight value Weight using the formula:

;

wherein the content of the first and second substances,，an ADC reference voltage is measured for the first signal detected by the second signal measuring ADC,measuring an ADC reference voltage for the second signal and equal to a supply voltage of the strain-gauge load cell, K being an amplification of the amplifier circuit,the measurement of the ADC is measured for the first signal,the maximum measurement value of the ADC is measured for the first signal in the measurement circuit.

Technical Field

The invention relates to the technical field of measurement and weighing, in particular to a temperature drift resistant weighing sensor signal measuring circuit.

Background

In modern society, the electronic weighing apparatus has huge use amount and is applied to various links of people's life and industrial production. In the design and debugging process of the weighing instrument, the sensor is required to provide signals of various weight values, the signals are amplified through the amplifier circuit, and finally the signals are detected by the signal measurement ADC and then sent to the MCU to be calculated to obtain the weight.

In the prior art, there are two main technical solutions as follows:

scheme a, as shown in fig. 1, has the advantages of: the voltage for supplying power to the sensor is directly supplied to the ADC to be used as the measurement reference voltage, so that the temperature characteristic of the measurement end is relatively good, and the influence of temperature change is small; the disadvantages are: since the signal (measured signal) given by the sensor is in the range of 0-15mV, in order to use a larger measurement range of the ADC (the measurement signal is closer to the range of 0-5V), a high-power amplifier (320 times) is needed, and due to the large amplification factor of the amplifier, the introduced noise is serious, which affects the signal processing in the later period.

Scheme B, as shown in fig. 2, has the advantages of: by means of resistance voltage division, 1V voltage (reference voltage which can be used by ADC at the minimum) is divided from homologous 5V voltage to serve as reference voltage, so that the times of amplification of a measured signal can be greatly reduced, the range of the measured signal can be close to the reference voltage by only 64 times of amplification, and signal noise caused by the fact that the amplification times are too large is reduced; the disadvantages are: since the reference voltage of the ADC is divided by the resistors, when the temperature changes, the reference voltage of the ADC changes due to different temperature characteristics of the resistors, and thus even if the measured signal does not change during measurement, the measurement result changes (temperature drift) during measurement of the instrument, which affects the measurement accuracy.

The two traditional technical schemes have respective advantages and disadvantages, but cannot simultaneously solve the problems of low-multiple measurement signal amplification (noise introduced by an amplifier) and temperature drift.

Disclosure of Invention

The technical problem to be solved by the embodiments of the present invention is to provide a temperature drift resistant weighing sensor signal measurement circuit to simultaneously solve the problems of low-multiple measurement signal amplification and temperature drift.

In order to solve the technical problem, the embodiment of the invention provides a temperature drift resistant weighing sensor signal measuring circuit, which comprises a strain gauge type weighing sensor, an MCU, a first signal measuring ADC, an amplifier circuit and a power supply, wherein the power supply comprises a 5V output end and a 3.3V output end, 5V output voltage is respectively provided for the strain gauge type weighing sensor, and 3.3V output voltage is provided for the MCU; the first signal measurement ADC is connected with the MCU and the amplifier circuit, the first signal measurement ADC detects a measured signal output by the strain gauge type weighing sensor through the amplifier circuit, the measurement circuit also comprises a second signal measurement ADC, a resistor R1 and a resistor R2, the resistor R1 is used for dividing voltage, a reference voltage end of the first signal measurement ADC detects the power supply voltage of the strain gauge type weighing sensor, two ends of the resistor R2 are respectively connected with two poles of a reference voltage end of the first signal measurement ADC, the second signal measurement ADC is connected and communicated with the MCU, a reference voltage end of the second signal measurement ADC detects the power supply voltage of the strain gauge type weighing sensor, a signal detection end of the second signal measurement ADC is connected with a reference voltage end of the first signal measurement ADC, and the MCU corrects the measured signal according to the change condition of the reference voltage of the first signal measurement ADC measured by the second signal measurement ADC, and calculating to obtain a weight value.

Further, the MCU calculates the Weight value Weight using the following equation:

;

wherein the content of the first and second substances,，an ADC reference voltage is measured for the first signal detected by the second signal measuring ADC,measuring an ADC reference voltage for the second signal and equal to a supply voltage of the strain-gauge load cell, K being an amplification of the amplifier circuit,the measurement of the ADC is measured for the first signal,the maximum measurement value of the ADC is measured for the first signal in the measurement circuit.

The invention has the beneficial effects that: the invention solves the problem of measured signal amplification factor and the problem of inaccurate measurement caused by the influence of temperature on the voltage division circuit.

Drawings

Fig. 1 is a circuit diagram of a prior art solution a.

Fig. 2 is a circuit diagram of prior art scheme B.

Fig. 3 is a circuit diagram of a temperature drift resistant load cell signal measurement circuit of embodiment 1 of the present invention.

Fig. 4 is a circuit diagram of a temperature drift resistant load cell signal measurement circuit of embodiment 2 of the present invention.

Detailed Description

It should be noted that the embodiments and features of the embodiments in the present application can be combined with each other without conflict, and the present invention is further described in detail with reference to the drawings and specific embodiments.

Referring to fig. 3 to 4, a temperature drift resistant load cell signal measurement circuit according to an embodiment of the present invention includes a strain gauge type load cell, an MCU, a first signal measurement ADC, an amplifier circuit, a power supply, a second signal measurement ADC, and a resistor R1 and a resistor R2 for voltage division.

The power supply comprises a 5V output end and a 3.3V output end, 5V output voltage is provided for the strain gauge type weighing sensor respectively, and 3.3V output voltage is provided for the MCU. The first signal measurement ADC is connected with the MCU and the amplifier circuit. The first signal measures SPI communication between ADC and the MCU, measures the signal that amplifier circuit enlargies. The first signal measurement ADC detects a measured signal output by the strain gauge type weighing sensor through the amplifier circuit, and the reference voltage end of the first signal measurement ADC detects the power supply voltage of the strain gauge type weighing sensor through the resistor R1. Two ends of the resistor R2 are respectively connected with two poles of a reference voltage end of the first signal measuring ADC.

The second signal measurement ADC is connected with the MCU for communication, a reference voltage end of the second signal measurement ADC detects the power supply voltage of the strain gauge type weighing sensor, a signal detection end of the second signal measurement ADC is connected with a reference voltage end of the first signal measurement ADC, and the MCU corrects the measured signal according to the change condition of the reference voltage of the first signal measurement ADC measured by the second signal measurement ADC, and calculates the weight value.

As an embodiment, the MCU calculates the Weight value Weight using the following equation:

;

wherein the content of the first and second substances,，an ADC reference voltage is measured for the first signal detected by the second signal measuring ADC,measuring an ADC reference voltage for the second signal and equal to a supply voltage of the strain-gauge load cell, K being an amplification of the amplifier circuit,the measurement of the ADC is measured for the first signal,for the first signal in the measuring circuit, the maximum measured value of the ADC is measured, and R1 and R2 are the resistances of the resistor R1 and the resistor R2, respectively.

Example 1: the strain-gauge type weighing sensor is a 4-wire strain-gauge type weighing sensor, as shown in fig. 3, the invention adds 1-way ADC, the second signal measurement ADC (i.e. ADC2 in fig. 3) adopts the sensor power supply voltage as the measurement reference voltage, and the reference voltage of ADC1 is measured (divided by the sensor power supply voltage), so that when the temperature changes, the ADC2 can measure the deviation generated by the reference voltage of ADC1 and inform the MCU, and the ADC1 also informs the MCU after measuring the sensor signal, and the MCU can correct the measured signal according to the change condition of the ADC1 reference voltage informed by the ADC 2. In the embodiment, a sensor strain gauge and a sensor wiring are not considered, only the internal measurement part of the instrument is considered, and the only part which has influence on the measurement is the voltage division circuit part (influenced by temperature, and the resistance value of a voltage division resistor changes), but the problem of measured signal amplification factor is solved and the problem of inaccurate measurement caused by the temperature influence of the voltage division circuit is also solved because two ADC chips are adopted to measure the sensor signal and the reference voltage signal respectively.

Example 2: the strain gauge type weighing sensor is a 6-wire strain gauge type weighing sensor, and as shown in fig. 4, when the long-wire connection of the sensors is considered, the on-line resistance is not negligible, so that a 6-wire solution method is adopted, and the double ADCs are also adopted to measure and correct 1-path sensor signals. Rb is a resistor on a transmission line, the actual sensor supply voltage in the circuit is changed into Vp, the reference voltage of the ADC2 adopts the voltage fed back by Vp through a line, and the reference voltage of the ADC1 adopts the reference voltage division of the ADC2 as the reference voltage. In the six-wire system connection, the connecting wires are equal in length, so that the resistances are equal, and when the temperature change is that the change proportion of Rb is the same, the signal change proportion is the same, so that the signal measurement is not influenced. And the only parts capable of influencing signal measurement are the voltage dividing circuits of R1 and R2. The change condition of the ADC1 reference voltage is measured through the ADC2 in the circuit and is informed to the MCU, after the ADC1 measures the sensor input signal, the MCU corrects the measurement signal result input by the sensor according to the change condition of the ADC1 reference voltage, so that the problem that the measurement is inaccurate due to temperature change can be avoided, and the problem of extra noise introduced by a high-multiple amplification circuit to the measurement is solved.

As shown in fig. 2, the prior art 4-wire system partial pressure measurement method: sensor supply voltageReference voltage of ADCVoltage dividing resistorR1， R2The amplifier amplification factor is K.

ADC measurement reference voltage；

ADC maximum code in the circuitCorresponding to a voltage value of；

At this time, if the ADC acquires the digital code of，

The sensor inputs the measurement result:

；

then we can go throughSensor range and sensor maximum input voltage (sensor sensitivity X)) A Weight value Weight is calculated.

;

;

It can be seen from the above formula that when the sensor is determined, the maximum measuring range of the sensor, the sensitivity of the sensor is a fixed and unchangeable value,and is also a constant value, for a 24bit adc,therefore, the weight calculation is only related to the voltage dividing resistorR1， R2Measured by ADCIt is related.

However when the temperature changesResistance value of the resistor becomesAnddue to the different temperature characteristics of the resistors, then there are

After the resistance change is not known in the above circuitIs not so great that the input voltage of the same nutrient will produce different measurement results with the temperature change.

Whereas in embodiment 1 of the present invention, the ADC2 partial circuit is for the ADC1 circuitMaking measurements, it can be knownIs known in the circuit of the ADC1To do soJust in the ADC2 circuitSo the above formula can be changed intoThrough the formula, we can calculateRather than the theoretical value of the designed circuit, then in the weight calculation formula(ii) a When R1 and R2 are changed, the actually measured values can still be usedAndcalculated to be trueThe accuracy of the weight calculation has been ensured.

In the 6-wire sensor connection method of embodiment 2, the reference voltage of the ADC2 is the voltage fed back from the sensor terminal, and the error caused by the attenuation part from the power supply terminal to the sensor terminal voltage is avoided. Namely, the reference voltage of the ADC2 and the reference voltage of the ADC1 circuit and the power supply voltage of the sensor are guaranteed to be a voltage source (Vp +, Vp-), so that even if the line resistance Rb changes, the reference voltage and the excitation source voltage of the measured signal are still homologous, and the measurement accuracy is guaranteed. The influence of the temperature change of the voltage-dividing resistor on the measurement part in the instrument can be eliminated by a double AD measurement method as the formula discussed in the four-wire system.

Therefore, the temperature drift generated by the voltage dividing resistor is corrected, so that the reference voltage actually used by the measurement ADC can be reduced in the measurement circuit by using a voltage dividing mode, the requirement on the amplification factor of the amplification circuit (including a separate amplifier or an amplifier inside the ADC) is reduced, and finally, the noise content and amplitude in the signal are reduced to obtain a better measurement result.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.