阅读说明：本技术 电阻传感器共模电压稳零电路及电阻式变送器 (Resistance sensor common mode voltage zero stabilization circuit and resistance type transmitter ) 是由 田英明 于 2019-11-12 设计创作，主要内容包括：本发明提供一种电阻传感器共模电压稳零电路及电阻式变送器,所述电阻传感器共模电压稳零电路在常规电位器式电阻传感器的结构基础上引入加法器和压控电阻电路,将电位器式电阻传感器输出的共模电压经加法器运算处理之后加载到压控电阻电路的控制端,同时,恒流源电流流过电位器式电阻传感器、压控电阻电路后最终流入负电源,形成了闭环控制回路；当环路稳定后,加法器的输出电压为0V,即电位器式电阻传感器输出端两个端子的电压之和为0V,也就是共模电压为0V,而差分电压不变,起到共模稳零作用,能有效解决后续差分放大器出现饱和并失去共模抑制能力的问题。(The invention provides a resistance sensor common-mode voltage zero-stabilizing circuit and a resistance-type transmitter, wherein the resistance sensor common-mode voltage zero-stabilizing circuit introduces an adder and a voltage-controlled resistance circuit on the basis of the structure of a conventional potentiometer-type resistance sensor, common-mode voltage output by the potentiometer-type resistance sensor is loaded to a control end of the voltage-controlled resistance circuit after being processed by the adder, and meanwhile, constant-current source current flows through the potentiometer-type resistance sensor and the voltage-controlled resistance circuit and finally flows into a negative power supply to form a closed-loop control circuit; when the loop is stable, the output voltage of the adder is 0V, namely the sum of the voltages of two terminals at the output end of the potentiometer type resistance sensor is 0V, namely the common-mode voltage is 0V, and the differential voltage is unchanged, so that the common-mode zero-stabilizing effect is achieved, and the problems that a subsequent differential amplifier is saturated and loses the common-mode rejection capability can be effectively solved.)

1. The utility model provides a resistance sensor common mode voltage stabilizes zero circuit, stabilizes zero to the common mode voltage of potentiometre formula resistance sensor output which characterized in that includes: an adder and a voltage-controlled resistance circuit;

the first fixed end of the potentiometer type resistance sensor is connected with a constant current source, the non-inverting input end of the adder is respectively connected with the sliding end and the second fixed end of the potentiometer type resistance sensor, the inverting input end of the adder is grounded, and the output end of the adder is connected with the control end of the voltage-controlled resistance circuit;

the input end of the voltage-controlled resistance circuit is connected with the second fixed end of the potentiometer type resistance sensor, and the output end of the voltage-controlled resistance circuit is connected with a negative power supply.

2. A resistive sensor common mode voltage zero stabilization circuit according to claim 1, wherein the potentiometer resistance sensor comprises a linear potentiometer resistance sensor.

3. The resistance sensor common-mode voltage zero-stabilizing circuit according to claim 1 or 2, further comprising a first resistor, a second resistor, a third resistor and a fourth resistor, wherein an output end of the adder is grounded through the first resistor and the second resistor which are sequentially connected in series, an inverting input end of the adder is connected with a common end of the first resistor and the second resistor, a sliding end of the potentiometer-type resistance sensor is connected with an non-inverting input end of the adder through the third resistor, and a second fixed end of the potentiometer-type resistance sensor is connected with a non-inverting input end of the adder through the fourth resistor.

4. A resistive sensor common mode voltage zero stabilization circuit according to claim 3, wherein the third resistor has a resistance equal to the fourth resistor.

5. The resistive sensor common mode voltage zero stabilization circuit of claim 4, wherein the adder comprises a dual power supply adder, a positive power supply pin of the dual power supply adder is connected to a positive power supply, and a negative power supply pin of the dual power supply adder is connected to the negative power supply.

6. The common-mode voltage zero-stabilizing circuit of the resistance sensor according to claim 5, wherein the voltage-controlled resistance circuit comprises an operational amplifier, a diode, an N-channel junction field effect transistor, a fifth resistor and a sixth resistor;

the non-inverting input end of the operational amplifier is connected with the output end of the adder, the inverting input end of the operational amplifier is grounded, the output end of the operational amplifier is connected with the cathode of the diode, the anode of the diode is connected with the grid electrode of the N-channel junction field effect transistor, and the anode of the diode is connected with the negative power supply through the fifth resistor;

and the drain electrode of the N-channel junction field effect transistor is connected with the second fixed end of the potentiometer type resistance sensor, and the source electrode of the N-channel junction field effect transistor is connected with the negative power supply through the sixth resistor.

7. The resistive sensor common mode voltage zero stabilization circuit of claim 6, in which the diode comprises a Schottky diode.

8. A resistance transmitter, comprising the resistance sensor common mode voltage zero stabilization circuit of any one of claims 1 to 7, wherein the resistance transmitter further comprises the potentiometer type resistance sensor, a differential amplifier and an analog-to-digital converter, the first fixed end of the potentiometer type resistance sensor is connected to a constant current source, the sliding end and the second fixed end of the potentiometer type resistance sensor are respectively connected to two input ends of the differential amplifier, and the output end of the differential amplifier is connected to the input end of the analog-to-digital converter.

9. The resistive transmitter of claim 8, wherein the differential amplifier comprises at least one of LMH6550, CLC 5526.

10. The resistive transmitter of claim 8 or 9, wherein the analog-to-digital converter comprises at least one of AD7811YRUZ, ADC12DL 065.

Technical Field

The invention relates to the field of industrial automation, in particular to a common-mode voltage zero-stabilizing circuit of a resistance sensor and a resistance transmitter.

Background

IN an industrial automatic two-wire system instrument, a potentiometer type resistance transmitter is structurally shown IN fig. 1 and comprises a potentiometer type resistance sensor RS, a differential amplifier and an analog-to-digital converter (AD converter), wherein a first fixed end of the potentiometer type resistance sensor RS is connected with a constant current source, a second fixed end of the potentiometer type resistance sensor RS is grounded, a sliding end of the potentiometer type resistance sensor RS is connected with an input end IN + of the differential amplifier, a second fixed end of the potentiometer type resistance sensor RS is connected with an input end IN-of the differential amplifier, and an output end of the potentiometer type resistance sensor RS is connected with an input end of the AD converter; the potentiometer type resistance sensor RS is driven by a constant current source, the output end of the potentiometer type resistance sensor RS generates differential voltage to a differential amplifier, and the output voltage Vo of the differential amplifier is in direct proportion to the resistance value connected to the differential amplifier.

When the maximum resistance of the potentiometer type resistance sensor RS is large, the common mode voltage input to the differential amplifier is large, for example, when the constant current source is 100uA and the maximum resistance of the potentiometer type resistance sensor RS is 20k Ω, the differential voltage V input at the two input ends of the differential amplifier is 100 × 10^-6*20*10³The common mode voltage is (2+ 0)/2-1V, which is very large, and the differential amplifier may saturate and lose the common mode rejection capability. Therefore, it is necessary to improve the circuit structure of the potentiometer resistance transmitter so that the common mode voltage input to the differential amplifier by the potentiometer resistance sensor in the potentiometer resistance transmitter is reduced.

Disclosure of Invention

In view of the above-mentioned drawbacks of the prior art, an object of the present invention is to provide a zero-stabilizing solution for common-mode voltage of a resistance sensor, which is used to solve the above-mentioned technical problems.

To achieve the above and other related objects, the present invention provides a common mode voltage zero stabilizing circuit for a resistance sensor, which stabilizes a common mode voltage output by a potentiometer-type resistance sensor, including: an adder and a voltage-controlled resistance circuit;

the first fixed end of the potentiometer type resistance sensor is connected with a constant current source, the non-inverting input end of the adder is respectively connected with the sliding end and the second fixed end of the potentiometer type resistance sensor, the inverting input end of the adder is grounded, and the output end of the adder is connected with the control end of the voltage-controlled resistance circuit;

the input end of the voltage-controlled resistance circuit is connected with the second fixed end of the potentiometer type resistance sensor, and the output end of the voltage-controlled resistance circuit is connected with a negative power supply.

Optionally, the potentiometer resistance sensor comprises a linear potentiometer resistance sensor.

Optionally, resistance sensor common mode voltage steady zero circuit still includes first resistance, second resistance, third resistance and fourth resistance, the output of adder is through establishing ties in proper order first resistance with ground connection behind the second resistance, the inverting input termination of adder first resistance with the common port of second resistance, potentiometre formula resistance sensor's slip end warp insert behind the third resistance the in-phase input of adder, potentiometre formula resistance sensor's second stiff end warp insert behind the fourth resistance the in-phase input of adder.

Optionally, a resistance value of the third resistor is equal to a resistance value of the fourth resistor.

Optionally, the adder includes a dual power supply adder, a positive power supply pin of the dual power supply adder is connected to a positive power supply, and a negative power supply pin of the dual power supply adder is connected to the negative power supply.

Optionally, the voltage-controlled resistance circuit includes an operational amplifier, a diode, an N-channel junction field effect transistor, a fifth resistor, and a sixth resistor;

the non-inverting input end of the operational amplifier is connected with the output end of the adder, the inverting input end of the operational amplifier is grounded, the output end of the operational amplifier is connected with the cathode of the diode, the anode of the diode is connected with the grid electrode of the N-channel junction field effect transistor, and the anode of the diode is connected with the negative power supply through the fifth resistor;

and the drain electrode of the N-channel junction field effect transistor is connected with the second fixed end of the potentiometer type resistance sensor, and the source electrode of the N-channel junction field effect transistor is connected with the negative power supply through the sixth resistor.

Optionally, the diode comprises a schottky diode.

In addition, in order to achieve the above and other related objects, the present invention further provides a resistance-type transmitter, including any one of the above resistance sensor common-mode voltage zero-stabilizing circuits, the resistance-type transmitter further includes the potentiometer-type resistance sensor, a differential amplifier and an analog-to-digital converter, a first fixed end of the potentiometer-type resistance sensor is connected to a constant current source, a sliding end and a second fixed end of the potentiometer-type resistance sensor are respectively connected to two input ends of the differential amplifier, and an output end of the differential amplifier is connected to an input end of the analog-to-digital converter.

Optionally, the differential amplifier comprises at least one of LMH6550, CLC 5526.

Optionally, the analog-to-digital converter comprises at least one of AD7811YRUZ, ADC12DL 065.

As described above, the common-mode voltage zero stabilization circuit of the resistance sensor of the present invention has the following beneficial effects: .

An adder and a voltage-controlled resistance circuit are introduced on the basis of the structure of a conventional potentiometer type resistance sensor, common-mode voltage output by the potentiometer type resistance sensor is loaded to a control end of the voltage-controlled resistance circuit after being operated and processed by the adder, and meanwhile, constant-current source current flows through the potentiometer type resistance sensor and the voltage-controlled resistance circuit and finally flows into a negative power supply to form a closed-loop control circuit; when the loop is stable, the output voltage of the adder is 0V, namely the sum of the voltages of two terminals at the output end of the potentiometer type resistance sensor is 0V, namely the common-mode voltage is 0V, and the differential voltage is unchanged, so that the common-mode zero-stabilizing effect is achieved, and the problems that a subsequent differential amplifier is saturated and loses the common-mode rejection capability can be effectively solved.

Drawings

FIG. 1 shows a block circuit diagram of a potentiometer-type resistance transmitter.

FIG. 2 is a block diagram of a resistive transmitter according to an embodiment of the present invention.

FIG. 3 is a circuit diagram of a resistance transmitter according to an embodiment of the present invention.

Description of the reference numerals

R1 first resistor

R2 second resistor

R3 third resistor

R4 fourth resistor

R5 fifth resistor

R6 sixth resistor

RS potentiometer type resistance sensor

Q1N channel junction field effect transistor

U1 adder

U2 operational amplifier

D1 diode

DVCC positive power supply

-VCC power supply

Output voltage of Vo differential amplifier

IN +, iN-differential amplifier input

Detailed Description

As mentioned in the foregoing background, in the potentiometer-type resistance transmitter shown in fig. 1, when the maximum resistance value of the potentiometer-type resistance sensor RS is large, the common mode voltage input to the differential amplifier is large, and the differential amplifier may be saturated and lose the common mode rejection capability.

Based on this, the invention provides a common mode voltage zero stabilization technical scheme of a resistance sensor, which stabilizes the common mode voltage output by a potentiometer type resistance sensor (a first fixed end of the potentiometer type resistance sensor is connected with a constant current source) driven by the constant current source, wherein the corresponding zero stabilization circuit comprises an adder and a voltage-controlled resistance circuit, the common mode voltage output by the potentiometer type resistance sensor is loaded to the input end of the adder, the output end of the adder is connected with the control end of the voltage-controlled resistance circuit, the input end of the voltage-controlled resistance circuit is connected with a second fixed end of the potentiometer type resistance sensor, and the output end of the voltage-controlled resistance circuit is connected with a negative power source.

Therefore, the zero stabilizing circuit forms a closed loop, the common-mode voltage output by the potentiometer type resistance sensor RS is loaded to the control end of the voltage-controlled resistance circuit after being operated and processed by the adder, the on-off state of the voltage-controlled resistance circuit is adjusted and the resistance of the voltage-controlled resistance circuit access circuit is adjusted, further regulating the electric potential at each position on the potentiometer type resistance sensor RS, the constant current source current flows through the potentiometer type resistance sensor RS and the voltage-controlled resistance circuit in sequence and finally flows into the negative power supply, therefore, the electric potential at each position on the potentiometer type resistance sensor RS is reduced, the common mode voltage is reduced on the premise that the differential voltage of the output voltage of the potentiometer type resistance sensor RS is not changed, finally, after the loop is stabilized, the output voltage of the adder is 0V, namely, the common mode voltage of the output voltage of the potentiometer type resistance sensor RS is 0V, and the common mode zero stabilizing effect is achieved.

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.

Please refer to fig. 2 to 3. It should be noted that the drawings provided in the present embodiment are only for illustrating the basic idea of the present invention, and the components related to the present invention are only shown in the drawings rather than drawn according to the number, shape and size of the components in actual implementation, and the type, quantity and proportion of the components in actual implementation may be changed freely, and the layout of the components may be more complicated. The structures, proportions, sizes, and other dimensions shown in the drawings and described in the specification are for understanding and reading the present disclosure, and are not intended to limit the scope of the present disclosure, which is defined in the claims, and are not essential to the art, and any structural modifications, changes in proportions, or adjustments in size, which do not affect the efficacy and attainment of the same are intended to fall within the scope of the present disclosure.

As shown in fig. 2 and 3, the present invention provides a resistance sensor common mode voltage zero stabilizing circuit for stabilizing zero of a common mode voltage output by a potentiometer type resistance sensor, including: an adder U1 and a voltage controlled resistance circuit;

the first fixed end of the potentiometer type resistance sensor RS is connected with a constant current source, the non-inverting input end of the adder U1 is respectively connected with the sliding end and the second fixed end of the potentiometer type resistance sensor RS, the inverting input end of the adder U1 is grounded (not shown in figure 2), and the output end of the adder U1 is connected with the control end of the voltage-controlled resistance circuit;

the input end of the voltage-controlled resistance circuit is connected with the second fixed end of the potentiometer-type resistance sensor RS, and the output end of the voltage-controlled resistance circuit is connected with a negative power supply VCC.

Optionally, the potentiometer resistance sensor RS comprises a linear potentiometer resistance sensor.

In detail, as shown in fig. 3, the common-mode voltage zero-stabilizing circuit of the resistance sensor further includes a first resistor R1, a second resistor R2, a third resistor R3, and a fourth resistor R4, an output end of the adder U1 is grounded through a first resistor R1 and a second resistor R2 which are sequentially connected in series, an inverting input end of the adder U1 is connected to a common end of the first resistor R1 and the second resistor R2, a sliding end of the potentiometer-type resistance sensor RS is connected to a non-inverting input end of the adder U1 through the third resistor R3, and a second fixed end of the potentiometer-type resistance sensor RS is connected to a non-inverting input end of the adder U1 through the fourth resistor R4.

Wherein, the resistance of the third resistor R3 is equal to the resistance of the fourth resistor R4.

Optionally, as shown in fig. 3, adder U1 comprises a dual power supply adder having a positive power supply pin connected to positive power supply DVCC and a negative power supply pin connected to negative power supply-VCC.

Optionally, as shown in fig. 3, the voltage-controlled resistor circuit includes an operational amplifier U2, a diode D1, an N-channel jfet Q1, a fifth resistor R5, and a sixth resistor R6;

the non-inverting input end of the operational amplifier U2 is connected with the output end of the adder U1, the inverting input end of the operational amplifier U2 is grounded, the output end of the operational amplifier U2 is connected with the cathode of a diode D1, the anode of a diode D1 is connected with the grid of an N-channel junction field effect transistor Q1, and meanwhile, the anode of a diode D1 is connected with a negative power supply-VCC through a fifth resistor R5;

the drain of the N-channel JFET Q1 is connected to the second fixed end of the potentiometer-type resistance sensor RS, and the source of the N-channel JFET Q1 is connected to the negative power supply VCC via a sixth resistor R6.

When the gate-source voltage Vgs of the N-channel jfet Q1 is within a certain range, the drain-source voltage is equivalent to a resistance controlled by the gate voltage.

Optionally, the operational amplifier U2 includes at least one of TLVs 2252, 2254. TLVs 2252 and 2254 are Texas Instruments (TI) two-way and four-way low voltage operational amplifiers, both of which have rail-to-rail output capability that can improve dynamic range in single supply or split supply applications.

Optionally, the diode D1 comprises a schottky diode, such as 1N5819 of TOSHIBA.

As shown in fig. 3, the resistance sensor common mode voltage zero stabilization circuit adopts dual power supplies (constant current source and negative power supply-VCC), the constant current source current flows through the potentiometer type resistance sensor RS and the voltage controlled resistance circuit and finally flows into the negative power supply-VCC, the non-inverting input end of the adder U1 is respectively connected with two terminals (i.e. the sliding end and the second fixed end) of the output end of the potentiometer type resistance sensor RS, the output of the adder U1 controls the voltage controlled resistance circuit, and a closed loop control loop is formed: when the output voltage of the adder U1 is greater than 0V, the output of the operational amplifier U2 is increased, the diode D1 is cut off, the N-channel junction field effect transistor Q1 is conducted, and the resistance of the N-channel junction field effect transistor Q1 is small, so that the common-mode voltage of the output voltage of the potentiometer type resistance sensor RS is reduced; finally, after the loop is stabilized, the output voltage of the adder U1 is 0V, that is, the sum of the voltages at the two terminals of the output end of the potentiometer type resistance sensor RS is 0V, that is, the common-mode voltage is 0V, and the differential voltage is not changed, so that the common-mode zero stabilizing effect is achieved.

IN addition, as shown IN fig. 2 and fig. 3, the present invention further provides a resistance transmitter, which includes the common-mode voltage zero-stabilizing circuit of the resistance sensor, and further includes a potentiometer-type resistance sensor RS, a differential amplifier and an analog-to-digital converter, wherein a first fixed end of the potentiometer-type resistance sensor RS is connected to a constant current source, a sliding end and a second fixed end of the potentiometer-type resistance sensor RS are respectively connected to two input ends IN +, IN-of the differential amplifier, and an output end of the differential amplifier is connected to an input end of the analog-to-digital converter.

Alternatively, the differential amplifier may employ a high performance, low distortion, low power application specific integrated chip, such as may include at least one of Texas Instruments (TI) LMH6550, CLC 5526.

Alternatively, the analog-to-digital converter may likewise employ a dedicated chip, such as may include at least one of AD7811YRUZ in idenao (AD), ADC12DL065 in Texas Instruments (TI).

In summary, the resistance sensor common-mode voltage zero-stabilizing circuit and the resistance-type transmitter provided by the invention introduce the adder and the voltage-controlled resistance circuit on the basis of the structure of the conventional potentiometer-type resistance sensor, load the common-mode voltage output by the potentiometer-type resistance sensor to the control end of the voltage-controlled resistance circuit after being processed by the adder, and meanwhile, the constant-current source current flows through the potentiometer-type resistance sensor and the voltage-controlled resistance circuit and finally flows into the negative power source to form a closed-loop control loop; when the loop is stable, the output voltage of the adder is 0V, namely the sum of the voltages of two terminals at the output end of the potentiometer type resistance sensor is 0V, namely the common-mode voltage is 0V, and the differential voltage is unchanged, so that the common-mode zero-stabilizing effect is achieved, and the problems that a subsequent differential amplifier is saturated and loses the common-mode rejection capability can be effectively solved.

The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.