阅读说明：本技术 一种三线制电阻传感器的测量电路及方法 (Measuring circuit and method of three-wire system resistance sensor ) 是由 申爽 吴晓刚 于 2021-01-05 设计创作，主要内容包括：本发明公开了三线制电阻传感器的测量电路及方法,其中电阻传感器核心电阻元件一端连接电阻传感器的第一接口,另一端连接电阻传感器的第二接口和第三接口；电路包括：至少两个电阻传感器；第一选择器,具有至少两路选择通道；第二选择器,具有至少一路选择通道；第一电阻；每个电阻传感器的第一接口连接至第一选择器的第一通道以及第二通道的数据输入端,第一选择器第一通道的输出端通过电阻连接至电源；第一选择器第二通道的输出端连接至第二选择器的第一数据输入端；每个电阻传感器的第二接口通过第一电阻连接至地,并且第一电阻远离地的接口连接至第二选择器的第二数据输入端；每个电阻传感器的第三接口分别连接至第二选择器的其他数据输入端。(The invention discloses a measuring circuit and a method of a three-wire system resistance sensor, wherein one end of a resistance sensor core resistance element is connected with a first interface of the resistance sensor, and the other end of the resistance sensor core resistance element is connected with a second interface and a third interface of the resistance sensor; the circuit comprises: at least two resistance sensors; the first selector is provided with at least two selection channels; the second selector is provided with at least one path of selection channel; a first resistor; the first interface of each resistance sensor is connected to the data input ends of the first channel and the second channel of the first selector, and the output end of the first channel of the first selector is connected to a power supply through a resistance; the output end of the second channel of the first selector is connected to the first data input end of the second selector; the second interface of each resistance sensor is connected to ground through a first resistance, and the interface of the first resistance remote from the ground is connected to the second data input end of the second selector; the third interface of each resistance sensor is connected to the other data input of the second selector.)

1. A measuring circuit of a three-wire system resistance sensor is characterized in that one end of a resistance sensor core resistance element is connected with a first interface of the resistance sensor, and the other end of the resistance sensor core resistance element is connected with a second interface and a third interface of the resistance sensor; the measurement circuit includes:

at least two of the resistive sensors;

the first selector is provided with at least two selection channels, each selection channel can realize one selection of M, wherein M is an integer greater than or equal to 2;

the second selector is provided with at least one selection channel, and the selection channel can realize one selection from N, wherein N is an integer greater than or equal to 4;

a first resistor;

the first interface of each resistance sensor is connected to the data input ends of the first channel and the second channel of the first selector, and the output end of the first channel of the first selector is connected to a power supply through a resistance; the output terminal of the second channel of the first selector is connected to the first data input terminal of the second selector; the second interface of each said resistive sensor is connected to ground through said first resistor and the remote interface of said first resistor is connected to the second data input of said second selector; the third interface of each resistance sensor is respectively connected to the other data input ends of the second selector; the output of the second selector is connected to the data processing circuit.

2. The measurement circuit of claim 1, further comprising:

a controller having an output terminal connected to an address input terminal of the first selector and/or the second selector.

3. The measurement circuit according to claim 1, wherein an enable terminal of the first selector and/or the second selector is connected to ground.

4. The measurement circuit of claim 1, further comprising: and the non-inverting input end of the non-inverting amplifier is connected with the output end of the second selector.

5. The measurement circuit of claim 4, further comprising: and the input end of the AD conversion circuit is connected with the output end of the non-inverting amplifier.

6. The measurement circuit of claim 1, wherein the number of resistance sensors is 4, and wherein M is 4 and N is 8.

7. The measurement circuit according to any one of claims 1 to 6, wherein the resistance sensor is a PT100 temperature sensor.

8. A measuring method of a three-wire resistive sensor applied to the measuring circuit according to any one of claims 1 to 7, characterized in that the resistance value of each resistive sensor core resistive element is sequentially obtained by controlling the on and off of the first selector and the second selector; the resistance value of the core resistance element of one of the resistance sensors is obtained through the following steps:

controlling two data input ends connected with the one resistance sensor in the first selector to be connected with corresponding output ends, and simultaneously controlling a first data input end of the second selector to be connected with a corresponding output end, so as to obtain a voltage V1 at a first interface of the one resistance sensor;

controlling a second data input end of the second selector to be connected with a corresponding output end, so as to obtain a voltage V2 at an interface where the first resistor is far away from the ground;

controlling a data input end connected with the third interface of the one resistance sensor in the second selector to be connected with a corresponding output end, so as to obtain a voltage V3 at the third interface of the one resistance sensor;

calculating a resistance value of the one resistive sensor core resistive element from the V1, the V2, and the V3.

9. The measurement method according to claim 7, wherein a predetermined data input terminal is controlled to be connected to a corresponding output terminal by inputting a predetermined 0, 1 code to an address input terminal of the first selector and/or the second selector through an output terminal of a controller.

Technical Field

The invention relates to the technical field of sensors, in particular to a measuring circuit and a measuring method of a three-wire system resistance sensor.

Background

A resistance sensor is a sensor that converts non-electrical physical quantities such as displacement, force, pressure, acceleration, and torque into changes in resistance values. A three-wire resistive sensor refers to a packaged finished sensor (i.e., a product that can be used without repackaging) having three interfaces, such as the PT100 temperature sensor shown in fig. 1. In fig. 1, the dotted box is a schematic internal cross-sectional view of the finished sensor, and 1 is a thermocouple or a thermal resistor, which is a core resistive element having two leads 2 and 3. When the sensor is packaged into a finished sensor product, the pin 2 is led out through one lead, and the pin 3 is led out through two leads, so that the finished sensor product has 3 leads. In actual use, a plurality of sensors such as the PT100 are often deployed, the number of the sensors is generally more than that of a controller, and the numerical values of the sensors are required to be read frequently so as to grasp environmental parameters in real time. How to read more sensor data in real time by fewer controllers, that is, how to realize multi-channel acquisition of sensor data, is one of the research focuses in the field.

Taking PT100 temperature sensor as an example, the prior art generally uses a full-bridge (as shown in fig. 2), a half-bridge (as shown in fig. 3) or a constant current source (as shown in fig. 4 and 5) to realize the measurement of "one" three-wire system resistance sensor. In fig. 2 to 5, RT1, RT2, RT3, and RT4 are resistance sensors to be measured, R1, R2, R3, and R4 are standard resistors, and I1 and I2 are constant current sources.

The inventor finds that the measurement is accurate by adopting a full-bridge or half-bridge mode, but at least two standard resistors need to be calibrated, and the measurement process is complicated; although the constant current source mode does not use a standard resistor, the constant current source circuit with high accuracy and low temperature drift is relatively complex. In addition, when the acquisition of multi-channel sensor data is realized by adopting full-bridge, half-bridge and constant current source modes, a switching circuit and an amplifying circuit are additionally added on the basis of multi-channel full-bridge, half-bridge or constant current source, so that the material cost of the existing measuring mode is higher, and the circuit is more complex.

Disclosure of Invention

In view of this, embodiments of the present invention provide a measurement circuit and a measurement method for a three-wire resistance sensor, so as to solve the problems of high material cost and complicated circuit and calibration in the existing manner of acquiring data of multiple sensors.

According to a first aspect, an embodiment of the present invention provides a measurement circuit of a three-wire resistive sensor, wherein one end of a resistive sensor core resistive element is connected to a first interface of the resistive sensor, and the other end is connected to a second interface and a third interface of the resistive sensor; the measurement circuit includes: at least two of the resistive sensors; the first selector is provided with at least two selection channels, each selection channel can realize one selection of M, wherein M is an integer greater than or equal to 2; the second selector is provided with at least one selection channel, and the selection channel can realize one selection from N, wherein N is an integer greater than or equal to 4; a first resistor; the first interface of each resistance sensor is connected to the data input ends of the first channel and the second channel of the first selector, and the output end of the first channel of the first selector is connected to a power supply through a resistance; the output terminal of the second channel of the first selector is connected to the first data input terminal of the second selector; the second interface of each said resistive sensor is connected to ground through said first resistor and the remote interface of said first resistor is connected to the second data input of said second selector; the third interface of each resistance sensor is respectively connected to the other data input ends of the second selector; the output of the second selector is connected to the data processing circuit.

Optionally, the measurement circuit further comprises: a controller having an output terminal connected to an address input terminal of the first selector and/or the second selector.

Optionally, the enable terminal of the first selector and/or the second selector is grounded.

Optionally, the measurement circuit further comprises: and the non-inverting input end of the non-inverting amplifier is connected with the output end of the second selector.

Optionally, the measurement circuit further comprises: and the input end of the AD conversion circuit is connected with the output end of the non-inverting amplifier.

Optionally, the number of the resistance sensors is 4, M is 4, and N is 8.

Optionally, the resistance sensor is a PT100 temperature sensor.

According to a second aspect, an embodiment of the present invention provides a measuring method for a three-wire resistive sensor, which is applied to the measuring circuit of the first aspect, and the resistance value of each resistive sensor core resistive element is sequentially obtained by controlling the on/off of the first selector and the second selector; the resistance value of the core resistance element of one of the resistance sensors is obtained through the following steps: controlling two data input ends connected with the one resistance sensor in the first selector to be connected with corresponding output ends, and simultaneously controlling a first data input end of the second selector to be connected with a corresponding output end, so as to obtain a voltage V1 at a first interface of the one resistance sensor; controlling a second data input end of the second selector to be connected with a corresponding output end, so as to obtain a voltage V2 at an interface where the first resistor is far away from the ground; controlling a data input end connected with the third interface of the one resistance sensor in the second selector to be connected with a corresponding output end, so as to obtain a voltage V3 at the third interface of the one resistance sensor; calculating a resistance value of the one resistive sensor core resistive element from the V1, the V2, and the V3.

Optionally, a predetermined data input terminal is controlled to be connected with a corresponding output terminal by inputting a predetermined 0, 1 code to an address input terminal of the first selector and/or the second selector through an output terminal of a controller.

The method provided by the embodiment of the invention can overcome the defect that the lead of the lead resistor obtains the resistance value of the core resistor element of the resistor sensor based on one standard resistor, and can be used without calibration or only once calibration, so that the measuring process is simpler, and the measuring result is more accurate; in addition, the measuring circuit has fewer peripheral elements, lower material cost and simple production process, and is convenient for large-scale mass production.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

Fig. 1 shows an internal structural schematic diagram of a three-wire PT100 temperature sensor;

FIGS. 2 to 5 are schematic diagrams showing a prior art measuring mode circuit configuration of a three-wire resistive sensor;

FIG. 6 shows a schematic diagram of a measurement circuit of a three-wire resistive sensor according to an embodiment of the present invention;

FIGS. 7A-7C are schematic diagrams illustrating a process of measuring one of the core resistive elements according to a measurement method of an embodiment of the present invention;

FIG. 8 shows a circuit schematic of a measurement method to calculate a core resistive element according to an embodiment of the present invention;

fig. 9A to 9C are schematic diagrams illustrating a process of measuring another core resistance element according to the measurement method of the embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The embodiment of the invention provides a measuring circuit of a three-wire resistance sensor. One end of the resistance sensor core resistance element is connected to the first interface of the resistance sensor, and the other end is connected to the second interface and the third interface of the resistance sensor, which may specifically refer to fig. 1.

As shown in fig. 6, the measurement circuit includes at least two resistance sensors (RT 1, RT2, RT3, and RT4 are core resistance elements of the resistance sensors in the figure), a first selector U1, a second selector U2, and a first resistor R1. The first selector U1 has at least two selection channels, each of which can select one from M, where M is an integer greater than or equal to 2; the second selector U2 has at least one selection channel, and the selection channel can realize one out of N, where N is an integer greater than or equal to 4.

As shown in fig. 6, the first interface (i.e., one end of the core resistive element) of each resistive sensor is connected to the data input terminals of the first channel and the second channel of the first selector U1, and the output terminal of the first channel of the first selector U1 is connected to the power supply through a resistor (which may be any resistor); the output of the second channel of the first selector U1 is connected to a first data input of a second selector U2; the second interface of each resistive sensor (i.e. the other end of the core resistive element) is connected to ground through a first resistor R1, and the distant interface of the first resistor R1 is connected to a second data input of a second selector U2; the third interface (i.e., the other end of the core resistive element) of each resistive sensor is connected to the other data input of the second selector U2; the output of the second selector U2 is connected to data processing circuitry.

The measurement manner of the measurement circuit will be described by taking the circuit shown in fig. 6, measurement RT1, and switching to measurement RT2 (see fig. 7A to 7C).

As shown in fig. 7A, the data input terminal X0 connected to the RT1 in the first selector U1 is first controlled to be turned on with the corresponding output terminal X, the data input terminal Y0 is controlled to be turned on with the corresponding output terminal Y, and the first data input terminal X0 of the second selector U2 is controlled to be turned on with the corresponding output terminal X, so that a current path shown by a thick solid line in fig. 7A is formed. I.e., the power source VREF is connected to the data processing circuit via the first selector U1 and the second selector U2 via the resistor R2 (arbitrary resistor), the core resistor element RT1 and the first resistor R1 in that order to ground, while at the same time the first interface of the resistor sensor (note not the core resistor element) is connected to the data processing circuit via the first selector U1 and the second selector U2. The voltage V1 at the first interface of the resistive sensor (note not the core resistive element) can thus be obtained.

As shown in fig. 7B, the second data input terminal X1 of the second selector U2 is controlled to be connected to the corresponding output terminal X, and at this time, the data input terminal X0 of the first selector U1 is kept connected to the corresponding output terminal X, and the data input terminal Y0 may or may not be connected to the corresponding output terminal Y. The voltage V2 at the interface of the first resistor R1 remote from the ground can thus be detected.

As shown in fig. 7C, the data input terminal X5 of the second selector U2 connected to the third interface of RT1 is then controlled to be connected to the corresponding output terminal, at this time, the data input terminal X0 of the first selector U1 and the corresponding output terminal X are kept in a connected state, and the data input terminal Y0 and the corresponding output terminal Y are kept in a connected state or not connected, so that the voltage V3 at the third interface of RT1 can be obtained.

Since the lead of the core resistance element is often led out through a long lead inside the resistance sensor, the influence of the resistance value of the lead on the measurement result is large and can not be ignored, and as shown by r in fig. 7A to 7C, the lead resistance of the three-wire resistance sensor is usually three equal-value resistances. Fig. 8 shows a simplified circuit diagram of the lead resistance and the circuit in which the measured voltage is present. As shown in fig. 8, since the subsequent circuits of the data input terminal X5 are usually high impedance circuits when V3 is obtained, no voltage drop occurs in the lead resistor connected to the data input terminal X5 (i.e., the lower left lead resistor R in fig. 8), and the voltage difference between V3 and V2 is the voltage drop in the lead resistor connected to the resistor R1 (i.e., the lower right lead resistor R in fig. 8). Assuming that the circuit in the circuit is I, it can be obtained from fig. 8:

V₂＝I·R₁——(1)

V₃-V₂＝I·r——(2)

V₁-V₂＝I·(RT₁+2·r)——(3)

according to the three formulas, the following formula can be obtained:

therefore, the method provided by the embodiment of the invention can overcome the defect that the lead of the lead resistor can obtain the resistance value of the core resistor element of the resistance sensor based on one standard resistor R1, and can be used without calibration or only once calibration, so that the measurement process is simpler, and the measurement result is more accurate; in addition, the measuring circuit has fewer peripheral elements, lower material cost and simple production process, and is convenient for large-scale mass production.

Given the procedure of measuring RT1 above, when it is necessary to switch to measuring RT2, it is only necessary to perform the following operations after the end of the procedure (see fig. 9A to 9C):

as shown in fig. 9A, the data input terminal X1 connected to the RT2 in the first selector U1 is first controlled to be turned on with the corresponding output terminal X, the data input terminal Y1 is controlled to be turned on with the corresponding output terminal Y, and the first data input terminal X0 of the second selector U2 is controlled to be turned on with the corresponding output terminal X, so that a current path shown by a thick solid line in fig. 9A is formed. I.e., the power source VREF is connected to the data processing circuit via the first selector U1 and the second selector U2 via the resistor R2 (arbitrary resistor), the core resistor element RT2 and the first resistor R1 in that order to ground, while at the same time the first interface of the resistor sensor (note not the core resistor element) is connected to the data processing circuit via the first selector U1 and the second selector U2. The voltage V1 at the first interface of the resistive sensor (note not the core resistive element) can thus be obtained.

As shown in fig. 9B, the second data input terminal X1 of the second selector U2 is controlled to be connected to the corresponding output terminal X, and at this time, the data input terminal X1 of the first selector U1 is kept connected to the corresponding output terminal X, and the data input terminal Y1 may be kept connected to the corresponding output terminal Y or not. The voltage V2 at the interface of the first resistor R1 remote from the ground can thus be detected.

As shown in fig. 9C, the data input terminal X4 of the second selector U2 connected to the third interface of RT2 is then controlled to be connected to the corresponding output terminal, at this time, the data input terminal X1 of the first selector U1 and the corresponding output terminal X are kept in a connected state, and the data input terminal Y1 and the corresponding output terminal Y are kept in a connected state or not connected, so that the voltage V3 at the third interface of RT2 can be obtained.

The resistance value of RT2 was calculated from the above V1, V2 and V3.

The resistance values of the resistors RT3 and RT4 can be measured through the method, so that multi-path collection of the resistor sensor is achieved.

It should be noted that the selector in the present application may be a chip of 74 series or other types currently sold in the market, or may be a unit or a module capable of implementing the function of the selector in the present application.

Optionally, the measurement circuit provided herein further comprises a controller having an output connected to an address input of the first selector U1 and/or the second selector U2.

Optionally, the enable terminals of the first and/or second selectors U1 and U2 are grounded.

Optionally, the measurement circuit provided by the present application further includes a non-inverting amplifier (high impedance device) having a non-inverting input connected to the output of the second selector U2.

Further, the measurement circuit provided by the present application further includes: and the input end of the AD conversion circuit is connected with the output end of the non-inverting amplifier. The output terminal of the AD conversion circuit may be connected to the input terminal of the controller, so that the resistance value of the core resistance element is calculated by the controller.

As an alternative to this embodiment, the number of the resistance sensors is 4, M is 4, and N is 8.

As an alternative to this embodiment, the resistance sensor is a PT100 temperature sensor.

The embodiment of the invention also provides a measuring method of the three-wire system resistance sensor, which is suitable for the measuring circuit. The measuring method sequentially obtains the resistance value of each resistance sensor core resistance element by controlling the on-off of a first selector U1 and a second selector U2; wherein, the resistance value of one of the resistive sensor core resistive elements is obtained through the following steps S1 to S4:

s1: two data input ends connected with one resistance sensor in the first selector U1 are controlled to be connected with corresponding output ends, and simultaneously, the first data input end of the second selector U2 is controlled to be connected with the corresponding output end, so that the voltage V1 at the first interface of one resistance sensor is obtained.

S2: the second data input of the second selector U2 is controlled to be connected to the corresponding output, thereby obtaining the voltage V2 at the interface of the first resistor remote from the power supply.

S3: and controlling a data input end connected with one resistance sensor in the second selector U2 to be connected with a corresponding output end, so as to acquire the voltage V3 at the third interface of one resistance sensor.

S4: the resistance of a resistive sensor core resistive element is calculated from V1, V2, and V3.

The above steps can be specifically described with reference to fig. 7A to 7C and fig. 9A to 9C.

Alternatively, predetermined data inputs are controlled to be connected to corresponding outputs by inputting predetermined 0, 1 codes to address inputs of the first and/or second selectors U1, U2 through outputs of the controller.

Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations fall within the scope defined by the appended claims.