JPH0529848B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a signal nonlinearity correcting device, and in particular to a device for correcting nonlinearity of the output of a thermocouple or other sensor using a non-contact method to obtain a linear output. The present invention relates to a nonlinearity correction device.

Prior Art An example of a conventional linearizer using an operational amplifier is shown in FIG. The nonlinear input signal V _IN is sequentially applied to two series-connected inverting amplifier circuits 1 and 2, and is also applied to parallel-connected ideal diode circuits 3 and 2.
4 and 5 at the same time. The output of each ideal diode circuit 3, 4 or 5 is selectively applied to the input side circuit or the output side circuit of the amplifier of the inverting amplifier circuit 1 by the corresponding changeover switch 6, 7 or 8. When applied to the input side circuit of the inverting amplifier circuit 1, negative polarity correction is performed, and when applied to the output side circuit, positive polarity correction is performed. 9 is a signal input terminal, and 10 is an output terminal of the linearizer.

The operation start point of each ideal diode circuit 3, 4 or 5 is determined by the respective corner setting terminal 11, 12 or 1.
It is determined by the break point setting voltage at 3.

To explain the operation of the linearizer shown in Figure 7,
If the magnitude of the non-linear input signal V _IN applied to the input terminal 9 exceeds the corner setting voltage at the corner setting terminals 11, 12 and/or 13, the ideal diode circuits 3, 4 and/or 5 becomes conductive. Depending on the operating position of the changeover switch 6, 7 or 8, the gain of the inverting amplifier circuit 1 changes and correction is applied to the input signal. It is well known that by providing a large number of ideal diodes, the broken line section can be shortened and the approximation accuracy can be improved.

In the conventional example shown in FIG. 7, switching the polarity of correction requires a switch operation, which is troublesome, and it is difficult to continuously adjust the amount of correction, simply turning the correction on and off. There was an inconvenience that only off adjustment was possible.

Problems to be solved by the invention Therefore, the problems to be solved by the invention are as follows:
The purpose of this invention is to eliminate the need for a switch operation for changing polarity in a linearizer, that is, a signal nonlinearity correction device, and to enable continuous adjustment of the amount of correction.

Means for Solving the Problems Referring to FIG. 1, the signal nonlinearity correction device according to the present invention adds the nonlinear input signal V _IN , which is the signal to be corrected, and the output of the correction amplifier circuit 30. Necessary corrections are made by addition by circuit 40. If necessary, the signal V _IN may be amplified to an appropriate level by the main amplifier 21.

A plurality of variable resistors 27, 28, 29 each provided with movable contacts 27a, 28a, 29a are connected in parallel to the input terminal of the correction amplifier circuit 30. Also, a signal proportional to the output V ₀ of the adder circuit 40
V ₁₁ is generated by voltage division or the like, and a signal V ₁₁ proportional to the output of the adder circuit is simultaneously applied to section detection circuits 23, 24, and 25 connected in parallel.

Each division _{detection circuit 23} , ₂₄ or 25 has specific set values V _s1 , _{V s2} and V _s3 ( ₌ V _so ,
(see Figure 2). When the signal V ₁₁ proportional to the output of the adding circuit exceeds the set value V _so , the division detection circuit 23, 24 or 25 detects the set value of the signal V ₁₁ proportional to the output of the adding circuit.
_The current I _o ( _{= I 1 ,}
I ₂ or I ₃ ) is the variable resistor 2 corresponding to the setting value.
The movable contact 27a, 28a or 29a of 7, 27 or 29 is made to flow.

In the present invention, since the input of the correction amplifier circuit 30 is the current I ₁ , I ₂ or I ₃ proportional to the above-mentioned excess, the movable contact 27a, 28a or 29a in the variable resistor 27, 28 or 29 By adjusting the position of the correction amplifier circuit 30, the output of the adder circuit 40 is
Correction of V ₀ , that is, linearization of the signal V _IN can be performed.

Function First, the operation of the division detection circuit 25 will be explained, but the operation of the other division detection circuits 23 and 24 will also be
They are the same except for the size of _Vso . The signal V ₁₁ on the input side of the division detection circuit 25 in the illustrated example is connected to the addition circuit 40
The output voltage _V0 is divided by the resistors _R11 and _R12 . Therefore, the change in this signal V ₁₁ is proportional to the change in the output voltage V ₀ of the adder circuit 40.

(1) When V ₁₁ is less than the specified set value V _s3 : The output of the amplifier IC is negative and the diode D
Due to the function of the transistor Q, the control signal is not transmitted to the transistor Q, and when the transistor Q is off, the variable resistor 29
The current I ₃ from is zero. At this time, the emitter voltage _V3 of transistor Q is given by the following equation.

V ₃ =V _s3 =(R ₁₃ Es)/(R ₁₇ +R ₁₃ )...(1) Here, _Es is the voltage of the reference voltage power supply 26. The voltage V ₃ in equation (1) is input to the negative input terminal of the amplifier IC of the section detection circuit 25.
That is, it matches the set value V _s3 of the third section detection circuit 25. Here, the calculation formula is derived using the voltage reference point as the negative side of the reference voltage power supply 26.

(2) When V ₁₁ exceeds the specified set value V _s3 : The output of the amplifier IC turns positive and the diode D
is turned on, the transistor Q becomes conductive, and a current I ₃ given by the following equation flows from the variable resistor 29.

I ₃ = (R ₁₇ + R ₁₈ ) (V ₁₁ −V _s3 )/R ₁₇・R ₁₈ ……(2) It should be noted that I ₃ exists only in the positive region, and Equation (2) As is clear from the above, the size of the load resistance, that is, the variable resistance 29 and the movable contact 29
The magnitude of the current _I3 is not affected by the potential of a, and is proportional to the difference ( _V11 - _Vs3 ) between the signal _V11 , which is proportional to the output _V0 of the adding circuit, and the set value _Vs3 . At this time, the emitter voltage V ₃ of transistor Q is (1)
I ₃ (R ₁₇ · R ₁₈ )/(R ₁₇ + R ₁₈ ) is added to the formula.

Note that the circuit consisting of the amplifier IC, transistor Q, and resistor _R18 is known as a constant current power supply using an OP amplifier. Further, the diode D is provided to prevent current from flowing backward from the transistor Q to the amplifier IC.

(3) FIG. 2 shows the variation of the moving contact current _Io , in this case _I3 .

In short, the division detection circuits 23, 24, 25
does not generate an output when the input signal is below the set value, and when the input signal exceeds the set value,
A current proportional to the amount exceeding the set value is generated in the variable resistance movable contacts 27a, 28a, and 29a.

Next, the operation of the correction amplifier circuit 30 will be explained.

(4) When there are no variable resistors 27, 28, and 29: The correction amplifier circuit 30 operates as a simple inverting amplifier circuit. Since the reference level for comparison at both input terminals is 0V, the potentials across the resistor _R19 are both 0V. Furthermore, since the correction amplifier circuit 30 operates to eliminate the potential difference between its two input terminals, e ₂ also becomes 0V.

(5) When variable resistors 27, 28, and 29 are present but there is no current in them (I ₁ to I ₃ = 0): e ₂ =
Since it is 0V and the potential difference between both input terminals is also 0V, the presence of these variable resistors has no effect at all.

(6) When there are variable resistors 27, 28, and 29, and only I ₃ flows, I ₁ = I ₂ = 0: When the movable contact 29a is in the center of the variable resistor 29 (Fig. 1) Resistance R ₁₉ Current flowing into the variable resistor 29 from the side
Since it can be designed so that i ₃₁ and the current ₃₂ flowing from the resistors R ₂₀ and R ₂₁ side to the variable resistor 29 are equal, the potential difference (e ₁ − e ₂ ) between the re-input terminals can be
Can be set to 0V. Therefore, the variable resistor 29 has no influence at all, the output E ₀ of the correction amplifier circuit 30 does not change, and the correction amount for the nonlinear input signal V _IN can be made zero.

When the movable contact 29a is located at the terminal on the _R19 side of the variable resistor 29 (Fig. 4), _E0 becomes negative so that the voltage drop ΔE across the variable resistor 29 due to the current ₃₂ becomes zero, and accordingly _e2 is also negative. Therefore, negative correction can be made to the non-linear input signal V _IN . Figure 5 shows the output voltage of the correction amplifier circuit 30.
Change amount ΔE ₀ (%) of E ₀ and output of adder circuit 40
The relationship with V ₀ (value expressed as a percentage of the rated output voltage value) is shown. The dotted line in the figure shows the range of change due to the variable resistor 29. The slope of this dotted line characteristic can be adjusted by adjusting the position of the movable contact 29a on the _R19 side of the variable resistor 29.

When the movable contact 29a is at the terminal on the e ₂ side (FIG. 3), E ₀ is positive and e ₂ is positive so that the voltage drop ΔE across the variable resistor 29 due to the current ₃₁ is zero. Therefore, positive correction can be made to the non-linear input signal V _IN . The positive side of the dotted line characteristic in FIG. 5 shows this.

Also, the slope of this dotted line characteristic is
This can be adjusted by adjusting the position of the movable contact 29a on the e ₂ side of 9.

(7) When there are variable resistors 27, 28, 29 and currents I ₁ , I ₂ and I ₃ of finite magnitude: As can be inferred from the above explanation of the function of the variable resistor 29, the section detection circuit 23 , ₂₄ and 25, the movable contacts 27, _{28a and} 2
9a and the variable resistors 27, 28, and 29, the variable regions shown by the solid line, the dashed line, the dotted line, and the hatching in FIG. 5, and the characteristics shown by, respectively, are obtained. It is noteworthy here that the current I ₃ is the summation circuit output voltage
When the value of V ₀ is less than 75%, there is no flow at all, so
No matter how the contactor 29a is operated in the circuit of current _I3 , an area below 75% will not be affected. This allows efficient correction without mutual interference between the plurality of divided areas.
The same applies to contacts 28a and 28b in the circuits for currents _I2 and _I1 .

Therefore, if the non-linear input signal V _IN and the correction amount E ₀ shown in FIG. Moreover, a linearizer is obtained in which the amount of correction can be continuously adjusted.

Embodiment In the embodiment of FIG. 1, the non-linear input signal V _IN is amplified by the main amplifier 21 and then applied to the adder circuit 40 of the present invention having the above configuration. Further, it is assumed that a zero adjustment circuit and a span adjustment circuit for adjusting the zero point of the output are included in the main amplifier 21 (not shown). In the figure,
Symbol 26 indicates a reference voltage power supply.

The correction effect of the embodiment shown in FIG. 1 will be explained in the case where the non-linear input signal V _IN is a sensor output having a characteristic shown in the solid line S-shape in FIG. 6 with respect to a physical quantity. The specific set values V _so of the segment detection circuits 23, 24 and 25 are 25%, 50% and 50% of the rated output voltage, respectively.
It is assumed that the setting corresponds to 75%. Adjustment at the point where the physical quantity input is 0% is performed by adjusting the output signal using the zero adjustment circuit (not shown) of the main amplifier 21.
This is done by making V ₀ zero.

The adjustment at the point where the physical quantity input is 25% is performed by main amplifier 2.
This is done by adjusting the span in step 1 (not shown). As a result, point P ₁ on the solid S-shaped characteristic in FIG. 6 can be corrected to point P ₂ on the linear characteristic. Therefore,
The characteristic of the output V ₀ with respect to the physical quantity input 0-25% after correction is a curve as shown by the dashed line. Further, the characteristic for physical quantity input of 25% to 50% is approximately a curve shown by a two-dot chain line.

Adjustment of the 50% physical quantity input point is performed by adjusting the position of the movable contact 27a on the variable resistor 27.
As a result, point P ₃ on the two-dot chain line characteristic in FIG. 6 can be corrected to point P ₄ on the linear characteristic. As mentioned above, this adjustment does not interfere with the region where the output is 25% or less. Physical quantity input after correction 25
The characteristic for -50% is a curve as shown by the dashed line. Although the output characteristics for a physical quantity input of 50% to 75% are complicated, for convenience of explanation, it is assumed that the curve is a two-dot chain line.

Adjustment of the 75% physical quantity input point is performed by adjusting the position of the movable contact 28a on the variable resistor 28.
As a result, point P ₅ on the two-dot chain line characteristic in FIG. 6 can be corrected to point P ₆ on the linear characteristic. Therefore, the characteristic for a physical quantity input of 50-75% after correction becomes a curve as shown by a dashed line. Also,
Adjustment by the movable contactor 28a does not interfere with the region where the output is 50% or less.

Adjustment of the 100% physical quantity input point is done using variable resistor 29.
This is done by adjusting the position of the upper movable contact 29a. As a result, point P ₇ on the two-dot chain line characteristic in Figure 6
can be corrected to point P ₃ on the linear characteristic.
Therefore, the characteristic for physical quantity input 75%-100% after correction also becomes a curve as shown by the dashed line.
Note that the adjustment by the movable contactor 29a does not interfere with the region where the output is 75% or less.

In this way, the nonlinear characteristic shown by the S-shaped solid line in Fig. 6 over the entire input span 0%-100% can be expressed as follows:
Extremely linear output as shown by the dashed line in the same figure
Can be corrected to V ₀ .

Effects of the Invention As explained above, the signal nonlinearity correction device according to the present invention obtains a correction amount using a correction amplifier circuit in which a plurality of variable resistors with movable contacts are connected in parallel to the input terminal. Since the correction amount and the input signal are added algebraically, the following effects are achieved.

(a) Since the polarity and magnitude of the correction amount can be continuously adjusted only by adjusting the position of the movable contact, precise correction can be easily realized.

(b) Since the polarity of the correction amount can be switched only by moving the movable contact, a changeover switch is not required and circuit adjustment is simplified.

(c) In the conventional correction device, since there is interaction between the constituent circuit elements, when adjusting the linearity, it is necessary to adjust the input span from 0% to 100% and then adjust it once for each node sequentially and then return it to 0%. Had to adjust back iteratively, but according to the invention 0%
The adjustment work is completed by adjusting once for each node from 100% to 100%.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a signal nonlinearity correction device according to the present invention, and FIG. 2 is an operating characteristic diagram of a division detection circuit.
Figures 3 and 4 are circuit diagrams for explaining the operation of the correction amplifier circuit, Figure 5 is a characteristic diagram of the correction amplifier circuit, and Figure 6 is a diagram for explaining the operation of the correction amplifier circuit.
The figure is an explanatory diagram of the operation of the device of the present invention, and FIG. 7 is a circuit diagram of a conventional nonlinearity correction device. 21... Main amplifier, 23, 24, 25... Division detection circuit, 26... Reference voltage power supply, 27, 28,
29...variable resistor, 27a, 28a, 29a...
Movable contactor, 30... Correction amplifier circuit, 40...
Addition circuit, V _IN ...Non-linear input signal, _V0 ...Output signal, _V11 ...Signal proportional to output signal _V0 , _Vso
(=V _s1 , V _s2 , V _s3 )...Set value.

Claims (1)

[Claims] 1. A correction amplifier circuit 30 in which n variable resistors with movable contacts are connected in parallel to the input terminal; an adder circuit 40 that adds the output of the correction amplifier circuit to the signal to be corrected V _IN ; A signal V ₁₁ proportional to the output and a corresponding input signal set value V _{so are} input, and when the signal proportional to the adder circuit signal exceeds a specific set value among the set values, the corresponding set value of the proportional signal is determined. n segmental detection circuits 23, 2 that output a current I _o proportional to the excess V ₁₁ −V _so
4 and 25, the output current I _o of each division detection circuit is added to the movable contact of the corresponding variable resistor, and a correction amplifier circuit output having a magnitude proportional to the amount exceeding the set value V ₁₁ −V _so is provided. A nonlinearity correcting device for a signal _VIN , which controls the slope of the output of the correction amplifier circuit over both positive and negative regions by adjusting the position of the movable contact in the variable resistor.