JPH04500856A - Linearization circuit and method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Linearization circuit and method Technical field The present invention relates to a linearization circuit and method for a signal conditioner of a remote sensor. . In particular, the linearization circuit and method according to the present invention can be applied to It can be applied to elements.

Background technology Temperature sensitive resistance conversion, as in the case of most types of impedance converters State-sensitive devices such as containers have temperature-dependent resistance and nonlinear electrical characteristics. have sex. In other words, the resistance of the state-sensitive element is directly proportional to the change in temperature of the state-sensitive element. For example, it does not change.

In circuits in which such transducers are often used, certain It is highly desirable to obtain an output signal that is linearly related to the sensitive state and to which the transducer can respond. This is desirable because the nonlinearity inherent in state-sensitive elements affects all circuits using state-sensitive elements. Due to the fact that it tends to amplify the nonlinearities of the body.

Various attempts have been made to solve these problems, and compared to other methods, One of the more common methods is to calculate the range of values of an electrical signal directly within a predetermined time interval. A method using line approximation has been proposed. However, such methods are expensive. as well as the size of the approximation interval over which this approximation error is used. There is also the problem that the curvature of the electrical characteristics increases depending on the degree of curvature.

Another attempt to solve the nonlinearity problem was published in the U.S. patent 4000 of Brakei. No. 454 and Regchen No. 4,556,330. however , the configurations disclosed in these U.S. patents are inefficient, have various drawbacks, and still remain unused. problems and it is imperative that these inefficiencies and shortcomings be overcome or eliminated. This is the object of the invention.

Disclosure of invention The present invention relates to a linearization circuit and method for remote sensor signal conditioning. In particular, linearization circuits and applications for state-sensitive devices such as temperature-sensitive resistors are and methods.

According to the present invention, an excitation current is applied to the state sensitive element by a constant current source. via a common junction between the state-sensitive elements. The voltage at the common junction is voltage - current A converter converts this current into a current that powers a remotely located signal conditioner. into a two-wire line that connects to the source. The output of the converter is passed through a feedback resistor. connected to a common junction to reduce the voltage as a result of changes in the electrical characteristics of the state sensitive element. changes the inverter output, thus making the regulation of the voltage at the common junction state-sensitive. produced by a corresponding adjustment of the excitation current applied to the element. In this way , a state-sensitive voltage that has a linear functional relationship to the state sensed by the state-sensitive element. maintained between both ends of the element. The first advantage of the configuration described above is that the constant current source can easily and continuously linearize state-sensitive devices excited by generates a voltage signal that is converted into current by a motor.

In the first embodiment of the invention described above, a constant current source, a state sensitive element and a voltage The power source is connected in series between the positive and negative terminals of the power source, and the converter is connected to the positive terminal of the power source. Ru. In this method, the constant current source and the converter are commonly biased. moreover , the junction between the output of the converter and the feedback resistor passes the power through another resistor. Connect to the negative terminal of the power source.

In a second embodiment of the invention, an additional constant current source and a resistor connected in series are integrated. Connected in parallel with a constant current source and a series-connected state-sensitive element, with an additional constant current source The junction between the resistor and the resistor is connected to an additional input of the voltage-to-current converter.

In a third embodiment of the invention, the other voltage source is added to the voltage-to-current converter. Connect between the input and the junction between the state-sensitive element and its series connected voltage source .

In the fourth embodiment of the present invention, a fixed value resistor is used in place of the voltage source in the first embodiment. establish. As discussed in further detail below, this embodiment uses a correction current or feedback This is particularly advantageous when the amount of current is such that the excitation does not occur in a very small part of the flow.

Therefore, the main object of the present invention is to provide a linearization circuit for a signal conditioner of a remote sensor. and a method.

Another object of the invention is to provide a linearization circuit for state sensitive elements such as temperature sensitive resistors. The purpose of this paper is to provide a method for

Another object of the present invention is that a constant current source applies an excitation current to the state sensitive element by applying these constant currents to the state sensitive element. A linearization circuit and method configured to apply via a junction between a source and a state-sensitive element. This is what we are trying to provide.

Another object of the invention is to reduce the voltage at the junction between the constant current source and the condition sensitive element. It seeks to provide a linearization circuit and method configured to convert Ru.

Another object of the invention is to use the current output of the converter to convert voltage to current to provide a constant configured to provide a feedback current at the junction between the current source and the state sensitive element. This paper attempts to provide a linearization circuit and method.

Another object of the invention is to combine an additional constant current source and a series connected resistor with a constant current source and a series connected resistor. This paper attempts to provide a linearization circuit and method connected in parallel with a state-sensitive element. be.

Another object of the invention is to provide additional inputs and state sensing to the voltage-to-current converter. a linearization circuit and It is intended to provide a method.

Another object of the invention is to connect a voltage source or a fixed value resistor in series with the state sensitive element. The present invention attempts to provide a linearization circuit and method that can be used.

The above objectives and other objectives are as described in the following detailed description, claims, and appendices. It will be more fully understood from the drawings.

1 ri of Huangsara Li FIG. 1 is a circuit diagram of a first embodiment of the linearization circuit of the present invention, and FIG. 2 is a circuit diagram of the linearization circuit of the present invention. FIG. 3 is a circuit diagram of a third embodiment of the linearization circuit of the present invention; FIG. 4 is a circuit diagram of a fourth embodiment of the linearization circuit of the present invention.

The present invention will be further described with reference to the attached drawings. will be explained in detail.

FIG. 1 is a circuit diagram of the first embodiment of the linearization circuit of the present invention. The linearization circuit 10 includes a power supply 12, a converter 14 that converts voltage into current, and a constant voltage flow source 16, temperature sensitive resistor 18, feedback resistor 19, and return path resistor 2 o and a voltage source 22.

Generally, the circuit elements described above are connected to a power supply 12 via their positive and negative terminals. The six circuits 10 forming the path are connected to a remote sensor comprising a temperature sensitive resistor 18. The temperature sensitive resistor 18 acts as a signal regulator and is controlled by a two wire circuit configuration. outputs a current output signal that is linearly proportional to the temperature applied.

Constant current source 16 serves as an excitation source or current sink that applies current Ix to the temperature sensitive resistor. It works. Junction 21 between current source 16 and resistor 18 is at the input of converter 14. connected to force and feedback resistor 19. converter 14 and current Sources 16 are preferably co-biased by power supply 12 via their positive terminals.

Converter 14 has at its output a voltage E appearing at the input of converter 14. A current signal having a linear functional relationship is given to the current signal, and this linear function is expressed by the following equation. Can be done.

11 = IQ + -E - (1) In the above equation, IO is the offset current, and is the voltage-to-current conversion coefficient ampere. /Volt “・” indicates double.

The output current IL of converter 14 is divided into two parts, one of which is connected to resistor 20. the other flows to the feedback resistor 19. At the input of converter 14 The voltage E is the voltage from the voltage source 22 and the temperature sensitive resistor 18 itself (excitation current generator x itself). This is the result of summing the voltage generated between both ends of the The excitation current is given by It will be done.

□8=1, -■,...(2) In the above equation, IR is the constant current from the constant current source 16, while IF is the resistance It changes according to the current resistance value R of 18. The value of current IF is given by the following formula .

In the above formula, E=V2+R7・Ix The resistance of the temperature sensitive resistor 18 is proportional to the temperature using the following equation.

RT=R-cho. (1+ce-t+β・tz)...(4) In the above formula , RTo is the resistance value at 0°C, and cc = 3.9xlo-' and β = -5,8X 10-' to -''.

Therefore, the following relationship holds true for the voltage at the input of converter 14:

In the above equation, ER=RTo・IR... (6) Equation (5) is the ratio of polynomials, and the following It can be rewritten as the formula.

In the above formula, r1=cc0(b-a゛c)・-(12)r,=(b-a-c)・[β-(a +1)・a・a”) −(13) The current of converter 14 is equal to input voltage E Since it is linearly proportional, in order to achieve linearization of this parameter, the equation (lO) is It is necessary to eliminate the quadratic term in .

By substituting equation (7) into equation (14), the feedback resistance RF is It can be expressed as

In the above formula, B=2・R^・A-Rr, ・(1-to-R^)...(17) C=A-R^" -RTo・R^・(1-に−R^)−RTll”・(1−に−R^)2... (18) Therefore, the voltage-to-current conversion coefficient K, resistance value R^, and RT If a value of 0°C is given, the feedback resistance RF can be calculated from equation (15) and the device's Output current can be linearized. For example, K=0.175 Amps/Volt If

RT. ;100 ohm, R^; 50 ohm, RF depth 19.5 kilo ohm becomes.

FIG. 2 is a circuit diagram of a second embodiment of the linearization circuit of the present invention. In this second figure The same symbols used in FIG. 1 are used for the same parts.

In the linearization circuit 10' of FIG. 2, another constant current source 32 is connected in series with the resistor 34. A circuit element connected in series with this resistor is connected to a constant current source 16 and a temperature The resistors 18 and 34 and the voltage source 32 are connected in parallel with the temperature sensitive resistor 18 at the junction point 27. are connected to each other.

Junction 33 between constant current source 32 and resistor 34 is an additional input of converter 14 Connected. For this reason, converter 14 has a differential input, i.e. The inverter 14 detects the voltage E1 between the current source 16 and the resistor 18, and also detects the voltage E1 between the current source 16 and the resistor 18. The voltage E2 between the resistor 2 and the resistor 34 is also detected.

FIG. 3 is a circuit diagram of a third embodiment of the linearization circuit of the present invention. Also in Figure 3, The same symbols used in Figure 1 are used for the same parts.

In the linearization circuit 10' of FIG. and a junction 27 between the temperature sensitive resistor 18 and the voltage source 22 .

In this example, converter 14 also detects voltage E1 between current source 16 and resistor 18. Converter 1 also detects voltage E2 at the positive terminal of voltage source 42. 4 has a differential configuration.

FIG. 4 is a circuit diagram of a fourth embodiment of the linearization circuit of the present invention. In this figure 4 The same reference numerals used in FIG. 1 are also used for similar parts.

In the linearization circuit 10'' of FIG. 4, the voltage source 2 used in the embodiment of FIG. 2 is replaced by a fixed value resistor 50. In other parts, the embodiment of FIG. This is the same as the embodiment shown in FIG. The embodiment shown in FIG.

The amount of correction current or feedback current IF is only a small fraction of the excitation current 1x. This is particularly suitable when there is no.

Furthermore, in the embodiment shown in FIG. 4, it will be noted that instead of the voltage source 22 of FIG. A fixed value resistor 50 of is equally useful in the implementations of FIGS. 2 and 3. sand That is, in FIGS. 2 and 3, in particular, the correction current or feedback current I Instead of the voltage source 22, if the amount of F is only a small fraction of the excitation current Ix. A fixed value resistor 50 can be used.

It should be noted that the power supply 12 in the circuits shown in FIGS. It can be used as an optional power source. Similarly, a converter 14 that converts voltage to current is It can be any convenient voltage-to-current converter and can be a constant current source 16 or and 32 may be any convenient constant current source known to those skilled in the art.

Although the present invention has been described in terms of preferred embodiment configurations, variations may be made within the scope of the invention. Of course, it can be implemented with some modifications.

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Claims (40)

[Claims] 1. excitation current means, the excitation current means applying an excitation current to the state sensitive element; connected to the state sensitive element at a common junction to cause the state sensitive element to respond to the excitation current means; configured to represent electrical characteristics, converter means, the input of the converter means being connected at the common junction point; said excitation current means and said state sensitive element, the electrical characteristics of said state sensitive element being connected to said exciting current means and said state sensitive element; When the voltage changes, the voltage at said common junction changes and the converter means converter means for converting the voltage at the common junction into a current and outputting the current from the converter means; configured, feedback means, the feedback means being in front of the converter means; connecting the output to the common junction to deliver a feedback current to the converter; adjusting the feedback current in response to the current at the output of the means; regulating the voltage at the common junction and the excitation current applied to the state sensitive element; , thereby generating a voltage that is a linear function of the state sensed by the state-sensitive element. a linearization circuit for a condition sensitive element configured to maintain pressure across said condition sensitive element; Road. 2. 2. The circuit of claim 1, wherein said state sensitive element comprises a temperature sensitive element. 3. 3. The circuit of claim 2, wherein said temperature sensitive element comprises a temperature sensitive resistor. 4. 4. The circuit of claim 3, wherein said excitation current means comprises a constant current source. 5. 5. The circuit of claim 4, wherein said feedback means comprises a feedback resistor. . 6. a first terminal connected to the excitation current means and supplying power to the state sensitive element; 2. The power supply means according to claim 1, further comprising a power supply means having a second terminal connected to the second terminal. circuit. 7. the state sensitive element is connected to the second terminal of the power supply means via a voltage source; 7. The circuit according to claim 6. 8. the state sensitive element is connected to a second terminal of the power supply means via a fixed value resistor; 7. The circuit according to claim 6. 9. Said feedback means communicates with said output of said converter means at another junction point. the other junction is connected to the second terminal of the power supply means through a resistor; 9. The circuit according to claim 8, wherein: 10. said feedback means at another junction point of said converter means; the other junction is connected to the second terminal of the power supply means through a resistor; 8. The circuit of claim 7, further comprising: 11. the first terminal of the power supply means supplying power to the converter means; 7. The circuit of claim 6, wherein: 12. The excitation current means and the converter means are connected in common by the power supply means. 12. The circuit of claim 11, which is voltage biased. 13. a circuit electrically connected in parallel with the excitation current means and the state sensitive element; The circuit further comprises a resistor and an additional excitation current for applying an additional excitation current to the resistor. additional excitation current means connected at a common junction, said additional common junction 2. A circuit according to claim 1, wherein the output point is connected to an additional input of said converter means. 14. 14. The circuit of claim 13, wherein the state sensitive element comprises a temperature sensitive element. 15. 15. The circuit of claim 14, wherein the temperature sensitive element comprises a temperature sensitive resistor. 16. at least one of the excitation control means and the additional excitation control means is constant; 16. The circuit of claim 15, comprising a current source. 17. 17. The feedback means of claim 16, wherein the feedback means comprises a feedback resistor. circuit. 18. a first commonly connected to said excitation current means and said additional excitation current means; and a second terminal commonly connected to the state sensitive element and the resistor. 14. The circuit of claim 13 further comprising power supply means. 19. The state sensitive element and the resistor are connected to the second voltage source of the power supply means via a voltage source. 20. The circuit of claim 18, wherein the circuit is connected to a terminal. 20. The state sensitive element and the resistor connect to the power source of the power supply means via a fixed value resistor. 20. The circuit of claim 18, wherein the circuit is connected to the second terminal. 21. said feedback means at another junction point of said converter means; the second terminal of the power supply means through another resistor; 21. The circuit of claim 20, connected to. 22. said feedback means at another junction point of said converter means; the second terminal of the power supply means through another resistor; 20. The circuit of claim 19, wherein the circuit is connected to. 23. the first terminal of the power supply means supplying power to the converter means; 20. The circuit of claim 18, wherein the circuit is connected. 24. said excitation current means, said additional excitation current means and said converter means; 24. The circuit of claim 23, wherein the circuit is commonly voltage biased by said power supply means. 25. connected between an additional input of said converter means and said state sensitive element. The circuit of claim 1 further comprising a voltage source. 26. 26. The circuit of claim 25, wherein the state sensitive element comprises a temperature sensitive element. 27. 27. The circuit of claim 26, wherein the temperature sensitive element comprises a temperature sensitive resistor. 28. 28. The circuit of claim 27, wherein said excitation current means comprises a constant current source. 29. 29. The method of claim 28, wherein the feedback means comprises a feedback resistor. circuit. 30. supplying power to a first terminal connected to the excitation current means and to the state sensitive element; 26. A power source as claimed in claim 25, further comprising power source means having a second terminal connected to circuit. 31. a first terminal at which said voltage source is connected to said additional input of said converter means; and a second terminal connected to the state sensitive element, the second terminal of the voltage source 31. The circuit of claim 30, wherein is also connected to said second terminal of said power supply means. 32. The state sensitive element and the resistor are connected to the second voltage source of the power supply means via a voltage source. 32. The circuit of claim 31, wherein the circuit is connected to a terminal. 33. The state sensitive element and the resistor connect to the second power source of the power supply means via a fixed value resistor. 32. The circuit of claim 31, wherein the circuit is connected to a terminal. 34. said feedback means at another junction point of said converter means; the second terminal of the power supply means through another resistor; 34. The circuit of claim 33, wherein the circuit is connected to. 35. said feedback means at another junction point of said converter means; the second terminal of the power supply means through another resistor; 33. The circuit of claim 32, connected to. 36. the first terminal of the power supply means supplying power to the converter means; 31. The circuit of claim 30, wherein the circuit is connected. 37. said excitation current means and said converter means are common by said power supply means; 37. The circuit of claim 36, wherein the circuit is voltage biased at . 38. Supplying an excitation current to a first end of a state sensitive element having a first terminal and a second terminal and the state sensitive element exhibits an electrical characteristic responsive to this, the state-sensitive element that changes as the electrical characteristics of the state-sensitive element change; detecting a voltage at the first terminal of the child; converting the voltage at the first terminal of the state-sensitive element into a current; At least a portion of the current resulting from this conversion is transferred to the A method for linearizing a state sensitive element, which includes a step of feedback to one terminal. 39. Changes in the current fed back during the feedback step adjusting the voltage at the first terminal of the state sensitive element according to 39. The method of claim 38, further comprising: 40. said state according to adjustment of the voltage at said first terminal of said state sensitive element. further comprising the step of adjusting the excitation current applied to the first terminal of the state-sensitive element, This causes a voltage that is a linear function of the state sensed by the state-sensitive element to be pre-determined. 40. The method of claim 39, wherein the state sensitive element is maintained across the state sensitive element.