JPH0239130B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a so-called linearizer that converts a non-linearly varying signal into a substantially linearly varying signal.

In general semiconductor pressure transducers, the ratio of change in output voltage to change in applied pressure gradually decreases as the pressure increases, as shown in Figure 1, and the output voltage to the magnitude of applied pressure gradually decreases as shown in Figure 1. The magnitude of the voltage does not change linearly.

This non-linearity of the output voltage with respect to the applied pressure does not have a large effect on measurement accuracy, so it is not a problem in normal measurements, but it may be useful when you want to widen the measurement range or when particularly high measurement accuracy is required. is done to linearize the output from the pressure transducer. Conventionally, this linearization has been performed by connecting a linearizer to the output of the pressure transducer that linearizes the signal using broken line approximation. In order to accurately correct changes in the output voltage, it is necessary to provide a large number of bending points, which has the disadvantage of significantly complicating the circuit.

In view of these conventional problems, the present invention enables highly accurate linearization with an extremely simple circuit.Examples of the present invention will be described below with reference to the drawings.

Figure 2 shows the basic circuit of the linearizer according to the present invention, in which a resistor R1 and a field effect transistor FET are connected in series between the input terminal 10 to which the non-linearly varying input signal ei is applied and the ground. The output signal eo is output from the connection point between the resistor R1 and the field effect transistor FET.

In this embodiment, the signal applied to the input terminal 10
ei is a negative signal, and in such a case, an N-channel depletion type field effect transistor FET is used. Then, the source terminal S of the field effect transistor FET is connected to the resistor R
1 to the input terminal 10, the drain terminal D is grounded, and the gate terminal G is connected to the input terminal 10.

In the above circuit, the field effect transistor
If the resistance between the source and drain of the FET is RSD, then
The output signal eo is now expressed by equation (1), and the electric field eo = RSD/RSD+R1・ei1/1+R1/RSD・ei...(1) The resistance RSD between the source and drain of the effect transistor FET is shown in Figure 3. As shown, it increases quadratically with respect to the magnitude of the negative voltage applied between the gate terminal G and the source terminal S.

Therefore, in equation (1), 1/(1+R1/
RSD) is the partial pressure ratio K, then this partial pressure ratio K is
When the absolute value of the input signal ei applied to the input terminal 10 is small, it takes a value considerably smaller than 1,
As the absolute value of the input signal ei increases, it takes a value closer to 1, and the voltage division ratio changes in a saturation characteristic. Therefore, the input/output characteristics of the linearizer shown in Fig. 2 are as shown in Fig. 4.
In a range where ei is small, the rate of change of the output signal eo with respect to a change in the input signal ei is small, and as the input signal ei becomes larger, the rate of change increases, taking characteristics close to a quadratic or cubic function curve. This characteristic can be changed by changing the size of the resistor R1 and the field effect transistor FET, and the resistor R1 and the field effect transistor FET are selected so that the change curve of the output signal eo with respect to the measured pressure, etc. approaches the closest to a straight line. will be held.

As a result, the signal output from the output terminal 11
eo has improved linearity and reduced measurement errors compared to the input signal ei.

FIG. 5 shows a more practical circuit of the circuit shown in FIG. 2, in which the signal input terminal 10 and the field effect transistor FET are connected through two resistors R1 and R2, and transistor
A resistor R3 is connected in parallel with the FET, and an output signal eo is taken out from the connection point between the resistors R1 and R2.

In this one, resistors R1, R2 and R
By changing the magnitude of 3 and the resistance ratio, it is possible to significantly change the change characteristics of the voltage division ratio K with respect to changes in the magnitude of the input voltage ei, so it is possible to perform linearization that is most suitable for the saturation characteristics of the input signal ei. can output signal
The linearity of eo can be further improved.

Alternatively, as shown in FIG. 6, a voltage obtained by dividing the input signal ei by resistors R4 and R5 may be applied to the gate terminal of the field effect transistor FET.
In this way, the linearization characteristic can also be changed by changing the ratio of resistors R4 and R5.
This is useful when the magnitude of the input signal ei is large.

Note that when the input signal is positive, the field effect transistor FET may be a P-channel depletion type transistor.

As described above, in the present invention, in a pressure transducer, a resistance and an electric field effect are applied to the input terminal to which a non-linear input signal in which the increase rate of the detection signal gradually decreases as the applied pressure increases. A voltage divider circuit consisting of a transistor is connected, and the voltage divided by the input signal is output as an output signal by this voltage divider circuit, and a voltage corresponding to the magnitude of the input signal is applied to the gate terminal of the field effect transistor. This is because the conduction resistance of the field effect transistor is changed by giving a signal, and the voltage dividing ratio of the voltage dividing circuit is thereby changed in accordance with the magnitude of the input signal to perform linearization. Linearization can be performed with a simple circuit, and the voltage applied to the detector does not change, unlike the method of linearization by changing the voltage applied to the detector of a pressure transducer, so the sensitivity to temperature changes is reduced. This has advantages such as ease of correction.

[Brief explanation of drawings]

Figure 1 is a diagram showing the relationship between applied pressure and output voltage in a general semiconductor pressure transducer, and Figures 2 to 6
The figures show an embodiment of the present invention, and FIG. 2 is a circuit diagram showing the configuration of a linearizer according to the invention, FIG. 3 is a diagram showing the characteristics of the field effect transistor in FIG. 2, and FIG. A diagram showing the input/output characteristics of the circuit shown in FIG. 2, and FIGS. 5 and 6 are diagrams showing modifications of the circuit shown in FIG. 2. 10...Input terminal, 11...Output terminal, FET...Field effect transistor, R1 to R5...Resistor.

Claims (1)

[Claims] 1 A linearizer for a pressure transducer that converts a nonlinear input signal in which the rate of increase of the detection signal gradually decreases as the applied pressure increases into an output signal that changes linearly using a voltage dividing circuit. The constituent voltage dividing circuit is composed of at least one resistor and a field effect transistor connected in series with the resistor and whose resistance between the source and the drain changes quadratically as the voltage applied to the gate terminal increases, The source terminal of this field effect transistor is connected via the resistor to the signal input terminal into which the input signal is input, the drain terminal is connected to the reference potential side, the gate terminal is connected to the signal input terminal, and the A linearizer for a pressure transducer, characterized in that a signal output terminal for taking out an output signal is connected between the resistor of the pressure circuit and the source terminal of the field effect transistor.