JPH09281157A - Signal processing circuit for sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the sensing operation of a sensor accurately with high detecting accuracy with a simple circuit configuration. SOLUTION: The signal processing circuit for sensor has a sensor element 11 in which a plurality of resistors R1 to R6 for the sensor are connected in series, the three resistor rows for the sensor are connected in parallel to form a resistance bridge. The potential between the two resistors of the plurality of the rows is input to comparators 2, 4, 6 for the sensor as sensor outputs, and the potential between the resistors of the two rows of the rows is input to a reference voltage forming circuit via a buffer amplifier 40 as a sensor output signal. The reference voltages of the comparators 2, 4, 6 is formed based on the output signal of the resistor, and input to the comparators 2, 4, 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal processing circuit for amplifying the output of a sensor and comparing it with a predetermined reference value to obtain the comparison result.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 2, for example, a circuit of a magnetic sensor element 1 has a resistor R1 assembled in a bridge shape.
The magnetic sensor element 1 includes R2, R3, and R4, and the comparators 2 and 4 to which the output signal of the magnetic sensor element 1 is input. The output between the resistors R1 and R3 is connected to the inverting input terminal of the comparator 2, and the output between the resistors R2 and R4 is connected to the inverting input terminal of the comparator 4. The output between the resistors R1 and R3 and the output between the resistors R2 and R4 of the magnetic sensor element 1 are in a relationship of a sine wave output and a cosine wave output. The output of the comparator 2 is connected to one end of the resistor R11 in series, and the comparator 4
Is connected to the other end of the resistor R12, and the output of the resistor R11,
The potential divided by R12 is input to the inverting input terminal of the comparator 6.

The power source of this circuit is such that the potential of the DC power source 10 is a resistor R21, a variable resistor R22, and a Zener diode 1.
The voltage is divided into a predetermined voltage of approximately 5V by 2 and the resistance R
The voltage is accurately set to 5 V by 23 and the buffer amplifier 14 and supplied to the sensor element 1. The voltage of 5V is divided into a predetermined potential and input to the comparators 2, 4 and 6. Regarding the potential input to the non-inverting input terminal of the comparator 2, the output of the buffer amplifier 14 is the resistors R24, R25,
The voltage is divided by the variable resistor R26 and the buffer amplifier 2
Precisely divided into 2.5V by 8 and output, resistance R
28, buffer amplifier 30, resistor R30, variable resistor R3
2 to the non-inverting input terminal of the comparator 2.
Similarly, the comparator 4 includes a Zener diode 3 between the output of the buffer amplifier 14 and the output of the buffer amplifier 28.
The potential between 1 and the resistor R34 is connected to the buffer amplifier 32, and the output thereof is connected to the non-inverting input terminal of the comparator 4 via the resistor R34 and the variable resistor R36.

[0004]

In the above-mentioned conventional technique, for example, when the sensor element 1 is an encoder, the output of the comparator 6 is changed by a change in the adjustment voltage due to a change with time or a change in temperature of each electronic element, and There has been a problem that the output of the element 1 and the reference voltage change separately, and a detection error occurs, which prevents accurate positioning. That is, the comparator 2,
4 and the predetermined reference voltage input to the comparator 6 and the output signal of the sensor element 1 which changes in a sinusoidal curve, each have an error in their output due to temperature change, change over time, etc.
The relative deviation of the signal voltage is a position detection error that appears as a deviation of the timing of the inversion timing of the output of the comparator 6.

The present invention has been made in view of the above problems of the prior art, and provides a sensor signal processing circuit having a simple circuit configuration, high detection accuracy, and accurate sensor detection operation. The purpose is to

[0006]

SUMMARY OF THE INVENTION According to the present invention, a plurality of sensor resistors are connected in series, and at least three sensor resistor rows are connected in parallel to form a resistor bridge. The potential between the resistors of the resistor string is input to the sensor comparator as a sensor output, and the potential between the resistors of two pairs of resistor strings in the resistor string is used as a sensor output signal through a buffer amplifier to form a reference voltage. This is a signal processing circuit for a sensor that is input to a circuit, forms a reference voltage of the sensor comparator based on the output signal of the sensor resistor, and inputs the reference voltage to the sensor comparator. A sensor output signal is extracted from between the resistors of the plurality of sensor resistors, and the sensor output signals in the three columns are three types of signals, a sine wave, a cosine wave, and a sine wave in which the positive and negative are reversed. And by the relative negative sine wave and the sine wave,
An average value of the sensor element output signal is formed, a reference voltage is set based on this average value, and the reference voltage is input to the sensor comparison circuit.

In the sensor signal processing circuit according to the present invention, the reference voltage input to the sensor comparator is formed on the basis of the output from the sensor element, and the reference voltage also changes in response to the change in the output of the sensor element. However, it enables an accurate comparison operation.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a sensor signal processing circuit according to an embodiment of the present invention, and this embodiment relates to a processing circuit connected to a sensor element 11 of a magnetic sensor. First, the sensor element 1 of this embodiment
Reference numeral 1 denotes resistors R1, R2, R3 and R which are resistors for sensors.
4, R5, R6 are connected in series one by one, and the resistor strings are connected in parallel in three lines, one end is connected to the power supply Vcc, and the other end is grounded. And the magnetic sensor element 1
The outputs between the resistors R1 and R3 in series and between the resistors R2 and R4 are connected to the inverting input terminals of the comparators 2 and 4 each including an operational amplifier. The output between the resistors R1 and R3 and the output between the resistors R2 and R4 of the magnetic sensor element 11 are in a relationship of sine wave output and cosine wave output. Further, the output between the resistors R5 and R6 is output as a negative sine wave having a polarity opposite to that of the output between the resistors R1 and R3.

The outputs of the comparators 2 and 4 are connected to both ends of resistors R11 and R12 in series, and resistors R11 and R1 are connected.
The potential divided by 2 is connected to the inverting input terminal of the comparator 6.

The output between the resistors R1 and R3 and the resistor R
The outputs between 5 and R6 are respectively connected to resistors R40 and R42, and the ends of the resistors R40 and R42 are connected in series to the resistor R40.
They are connected to both ends of 43 and 44, respectively. Resistors R43, R
The output between 44 is connected to the non-inverting input terminal of the buffer amplifier 40. Further, the resistors R42 and R40 are installed by connecting capacitors 45 and 46 in series, respectively, and the non-inverting input terminal of the buffer amplifier 40 is also connected to the capacitor 47.
Is installed through.

The output of the buffer amplifier 40 is a resistor R48.
Is connected to the power supply Vcc via the resistor R50, and the resistors R49 and R51, which are reference voltage forming circuits, are connected together.
Grounded. And the resistance R50 and the resistance R
The contacts of the resistor 51 on the side of the resistors R48, R49 are respectively connected to both ends of the variable resistors R53, R54, R55 connected in parallel. And the variable resistors R53, R54, R
The middle terminal of 55 is connected to the non-inverting input terminal as the reference voltage of the comparator 6 and the comparators 2 and 4, and further, the variable resistor R5
The middle terminals of 3, R54, and R55 are capacitors 48,
It is grounded via 49 and 50.

The sensor signal processing circuit of this embodiment is
The potential between the resistors R1 and R3 of the magnetic sensor element 11 is output as a sine wave output signal, and the potential between the resistors R2 and R4 is output as a cosine wave output signal, which are input to the inverting input terminals of the comparators 2 and 4, respectively. . The reference voltage of the variable resistors R54 and R55 is input to the non-inverting input terminals of the comparators 2 and 4. This reference voltage is the resistance R of the sensor element 11.
1, R3 and resistors R5 and R6, the positive and negative sine wave average potentials are extracted by a smoothing circuit including resistors and capacitors, and are set as average value potentials from which noise is removed.

To set the reference voltage by the output signal of the sensor element 11, first, the output between the resistors R1 and R3 and the output between the resistors R5 and R6, which are signals whose positive and negative signs are opposite to each other, are set to the resistors R40 and R42. Connected to the resistors R43 and R44, and further to the capacitors 45 and 46 to smooth them, and input to the non-inverting input terminal of the buffer amplifier 40 as an output between the resistors R43 and R44 at the midpoint thereof to obtain an average voltage. ing. Moreover, noise is further removed by the capacitor 47.

The output of the buffer amplifier 40 is connected to resistors R50, R48, R49 and R5 with respect to the power source Vcc.
It is connected between the resistors R48 and R49 of No. 1 and outputs the average value of the output of the sensor element 11. Variable resistor R5
Both ends of 3, R54 and R55 are connected between respective potentials of which the output of the buffer amplifier 40 is adjusted to be positive and negative by resistors R48 and R49, thereby enabling the offset adjustment of the comparators 2 and 4.

According to the signal processing circuit for sensor of this embodiment, the output of the sensor element 11 is taken out as three kinds of output of sine wave output, cosine wave output, and negative sine wave output, and the average value thereof is used as the sensor. Since it is set as the reference voltage of the comparators 2, 4, 6 for use with the sensor, the reference voltage also fluctuates correspondingly to the fluctuation of the sensor element 11 and the power supply voltage, and the error in discriminating the output of the sensor element 11 is reduced. are doing.

As a result, the error of the discrimination signal becomes extremely small, and in the case of the sensor signal processing circuit of the encoder,
It is possible to increase the number of pairs of comparison circuits including the resistors R11 and R12 that process the sensor output and the comparator 6 to increase the number of potential divisions by the resistors R11 and R12, and improve the detection accuracy of the encoder. it can.

In addition to the above embodiment, the sensor signal processing circuit of the present invention detects the average value of the sensor output by an appropriate smoothing circuit or filter, appropriately processes the detected voltage, and outputs the detected voltage as a reference to the comparator. Anything that can be input as a voltage will do. Further, the sensor element may be used as a sensor element other than the magnetic sensor. Further, the amplified sensor output may be processed by another processing circuit such as A / D conversion and digital processing.

[0018]

The sensor signal processing circuit of the present invention can improve the accuracy of the sensor and reduce the influence of noise. Furthermore, when it is used for an encoder or the like, it is possible to improve the measurement accuracy and enable stable measurement over a long period of time.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of a sensor signal processing circuit according to the present invention.

FIG. 2 is a circuit diagram of a conventional sensor signal processing circuit.

[Explanation of symbols]

 1, 11 Sensor element 2, 4, 6 Comparator 14, 28, 30, 32, 40 Buffer amplifier

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yozo Ohara 3158 Shimookubo, Osawano-cho, Kamishinkawa-gun, Toyama Prefecture Hokuriku Electric Industry Co., Ltd.

Claims (2)

[Claims] 1. A plurality of resistances for a sensor are connected in series and a plurality of sets are provided, a bridge is formed by a set of each resistance series, and a potential between the resistances of two resistance series among them is compared for a sensor. To the reference voltage forming circuit via the buffer amplifier, and the output signal between the resistances of the two resistance series of the plurality of resistance series is input to the reference voltage forming circuit, and based on the output signal of the sensor resistance, A sensor signal processing circuit for forming a reference voltage of the sensor comparator and inputting the reference voltage to the sensor comparator. 2. A plurality of sensor resistors are connected in series and provided in a plurality of sets, and a sensor output signal is taken out from among the resistors of the plurality of sensor resistors, and at least three sets of the resistor rows are provided. The sensor output signals of the resistor trains are three types of signals, a sine wave and a cosine wave, and a sine wave in which positive and negative are inverted, and the sensor output signal is a negative sine wave. A sensor signal processing circuit in which a reference voltage is formed from an average value of sensor element output signals and the reference voltage is input to the sensor comparison circuit.