JP2017173073A - Analog sensor temperature compensation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an analog sensor temperature compensation device that can simply perform a temperature drift compensation, using a digital control signal from a microcomputer and the like.SOLUTION: In an analog sensor temperature drift compensation device 10, a sensor output after subjected to a scale drift compensation via a first digital potentiometer 21 to be adjusted by a control unit 11 based on an ambient temperature to be detected by a temperature sensor 12 is input to an operational amplifier 23. An offset drift compensation-purpose second digital potentiometer 22 connected to an input side of the operational amplifier 23 is adjusted by the control unit 11 on the basis of the ambient temperature, and thereby a sensor output S1 after subjected to the offset drift compensation is output from an output terminal of the operational amplifier 23.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a temperature compensation device for an analog sensor, and more particularly to a temperature compensation device for an analog sensor that uses a microcomputer or the like to compensate for offset drift and scale drift included in the sensor output of the analog sensor due to ambient temperature.

  As an analog sensor, as described in Patent Document 1, a semiconductor position detecting device (see FIG. 1) that can detect the light receiving position based on the ratio of the both ends output current, with the output current at both ends changing according to the light receiving position on the light receiving surface. PSD) is known.

  In such an analog sensor, in general, compensation is performed in the sensor processing circuit by feeding back the output current at both ends to adjust the light emission amount of the light emitting element so that the light reception amount on the light receiving surface becomes constant. A circuit is provided. In addition, the analog sensor (optical potentiometer) described in Patent Document 1 is also provided with a compensation circuit for ensuring linearity between the rotation angle of the rotating disk to be detected and the sensor output.

Japanese Patent Laid-Open No. 10-185624

  In an analog sensor, the characteristics of a light emitting element, a light receiving element, and other elements constituting the sensor processing circuit vary due to a change in ambient temperature. Only the built-in compensation circuit may not sufficiently compensate for variations in sensor output.

  Analog sensors generally have an offset drift that is 10 times greater than that of digital sensors. There is almost no DS scale drift. Although it is desirable to use a digital sensor in order to construct a sensor system that performs a detection operation accurately without being affected by the ambient temperature, the digital sensor is more expensive than an analog sensor.

  In view of these points, an object of the present invention is to provide an analog sensor temperature compensation device that can easily perform temperature drift compensation using a digital control signal from a microcomputer or the like.

In order to solve the above-described problem, the present invention provides a temperature drift compensation device that compensates for a scale drift and an offset drift due to a change in ambient temperature with respect to a sensor output of an analog sensor,
A first digital potentiometer for scale drift compensation;
A second digital potentiometer for offset drift compensation;
An operational amplifier,
The first digital potentiometer is adjusted based on a preset scale drift compensation amount with respect to the ambient temperature, and the second digital potentiometer is adjusted based on an offset drift compensation amount preset with respect to the ambient temperature. A control unit,
Have
The sensor output before compensation is supplied to the input of the operational amplifier via the first digital potentiometer,
The second digital potentiometer is connected to the input side of the operational amplifier,
The operational amplifier outputs the sensor output after the scale drift and the offset drift are compensated.

  In the present invention, a digital potentiometer that can be directly adjusted by a digital device such as a microcomputer can be used to individually compensate for a scale drift and an offset drift due to a change in ambient temperature of the sensor output.

  In this case, the temperature sensor can be arranged to detect the ambient temperature of the analog sensor, and temperature compensation can be performed by a control unit configured by a microcomputer or the like based on the detected ambient temperature.

  For example, during temperature aging of an actuator or other device with an analog sensor installed, the temperature drift amount (scale drift amount and offset drift amount) of the sensor output with respect to the ambient temperature is detected and scaled according to the ambient temperature. The drift compensation amount and the offset drift compensation amount are set and stored in the control unit. In actual control, the temperature compensation of the sensor output may be performed by adjusting the first and second digital potentiometers using the temperature compensation amount associated with the ambient temperature detected by the temperature sensor.

It is a schematic block diagram which shows an example of the temperature compensation apparatus of the analog sensor to which this invention is applied.

  With reference to FIG. 1, a temperature compensation device for an analog sensor according to the present embodiment will be described. First, the analog sensor 1 includes an optical detection unit including a light emitting element 2 such as an LED and a light receiving element 3 such as a one-dimensional semiconductor position detection element. Between the light emitting element 2 and the light receiving element 3, for example, a rotating slit disk 4 in which a spiral slit is formed is disposed, and the detection light emitted from the light emitting element 2 as the rotating slit disk 4 rotates. The passing position moves in a linear direction on the light receiving surface of the light receiving element 3. In the light receiving element 3, the output signals A and B at both ends thereof change according to the light receiving position of the detection light on the light receiving surface.

  The output signals A and B are amplified through the amplifiers 5 and 6, respectively, and then added by the adder 7 to obtain a difference from a preset reference current value. This difference is amplified through an amplifier (not shown) and then fed back to the drive current of the light emitting element 2. Thus, the amount of light received by the light receiving element 3 is controlled to be constant, and therefore the sum of the output signals A and B at both ends thereof is maintained constant.

  In this manner, the output signals A and B are obtained in a state where the received light amount is kept constant by the feedback control. The difference between the output signals A and B is obtained by the comparator 8, and the obtained difference signal is output as the sensor output S 0 of the analog sensor 1.

  The sensor output S0 of the analog sensor 1 is supplied to the temperature compensation device 10. The temperature compensation device 10 includes a control unit 11 composed of a microcomputer, a temperature sensor 12 that detects the ambient temperature of the analog sensor 1, and a temperature compensation circuit that performs temperature compensation on the sensor output S0 under the control of the control unit 11. 13.

The temperature compensation circuit 13 includes a first digital potentiometer 21 for scale drift compensation, a second digital potentiometer 22 for offset drift compensation, and an operational amplifier 23 having two inputs and one output. The sensor output S0 output from the analog sensor 1 is input to the operational amplifier 23 (inverting amplifier) via the first digital potentiometer 21. A second digital potentiometer 22 is connected to the input side of the operational amplifier 23. The sensor output S1 after temperature compensation is output from the output terminal of the operational amplifier 23 and supplied to a higher-level device (not shown).

  An ambient temperature detected by the temperature sensor 12 is input to the control unit 11. The control unit 11 holds a correspondence table or a relational expression between the ambient temperature, the scale drift compensation amount, and the offset drift compensation amount. For example, a correspondence table of the ambient temperature, the scale drift compensation amount, and the offset drift compensation amount is stored and held in the memory 11a. The scale drift compensation amount and the offset drift compensation amount are held as adjustment values of the first and second digital potentiometers 21 and 22, respectively.

  In the actual control operation, the control unit 11 searches the adjustment values of the first and second digital potentiometers 21 and 22 with reference to the correspondence table using the detected ambient temperature, and uses these adjustment values. As described above, the first and second digital potentiometers 21 and 22 are adjusted. As a result, the sensor output S0 is supplied to the operational amplifier 23 after the first digital potentiometer 21 is compensated for the scale drift caused by the change in the ambient temperature. Further, by adjusting the second digital potentiometer 22, the output terminal of the operational amplifier 23 outputs the sensor output S1 in which the offset drift due to the change in the ambient temperature is compensated.

  Note that the temperature drift compensation amount can be set based on a temperature drift amount (scale drift amount, offset drift amount) caused by a change in ambient temperature measured in advance. For example, when temperature aging is performed after assembly of a finite rotation motor to which a rotating slit disk is attached, the temperature drift amount of the sensor output caused by the ambient temperature change is measured, and the temperature drift compensation amount is set based on this.

  Although the above example is an optical sensor in which the analog sensor includes a light emitting element and a light receiving element, the present invention can be used as a temperature compensation device for other analog sensors.

DESCRIPTION OF SYMBOLS 1 Analog sensor 2 Light emitting element 3 Light receiving element 4 Rotary slit disk 5, 6 Amplifier 7 Adder 8 Comparator 10 Temperature compensation apparatus 11 Control part 11a Memory 12 Temperature sensor 13 Temperature compensation circuit 21 1st digital potentiometer 22 2nd digital potentiometer 23 Operational amplifier S0 Sensor output S1 Sensor output

Claims (2)

A temperature drift compensator that compensates for scale drift and offset drift caused by changes in ambient temperature with respect to sensor output of an analog sensor,
A first digital potentiometer for scale drift compensation;
A second digital potentiometer for offset drift compensation;
An operational amplifier,
The first digital potentiometer is adjusted based on a preset scale drift compensation amount with respect to the ambient temperature, and the second digital potentiometer is adjusted based on an offset drift compensation amount preset with respect to the ambient temperature. A control unit,
Have
The sensor output before compensation is supplied to the input of the operational amplifier via the first digital potentiometer,
The second digital potentiometer is connected to the input side of the operational amplifier,
A temperature compensation device for an analog sensor, in which the sensor output after the scale drift and the offset drift are compensated is output from the operational amplifier. A temperature sensor for detecting the ambient temperature of the analog sensor;
The control unit, based on the ambient temperature detected by the temperature sensor, the scale drift compensation amount and the offset drift compensation amount stored and held in a form associated with the ambient temperature, the first, The temperature compensation device for an analog sensor according to claim 1, wherein the second digital potentiometer is adjusted.

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