JPH1188165A - Input device and input method for analog signal and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure A/D conversion accuracy even when a voltage unstable with respect to temperature is used for a reference voltage. SOLUTION: The device is provided with an A/D converter 214 that converts an analog signal 212 into a digital signal 215 and a microcomputer 270. In the input device 201 for the analog signal that provides an output of the digital signal 215 externally, a 1st reference voltage 252 being a reference of A/D conversion and a 2nd reference voltage 282 with temperature stability are given to the A/D converter 214, and the microcomputer 270 corrects an A/D conversion error of the analog signal 212 based on temperature fluctuation in the 1st reference voltage 252 by using the A/D conversion value 263 of the 2nd reference voltage 282 as a specified value.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an analog signal input device, an analog signal input method, and a recording medium. Input device, method, and recording medium.

[0002]

2. Description of the Related Art A conventional analog signal input device will be described with reference to FIG. FIG. 4 is a block diagram of a conventional analog signal input device. An analog input signal (current or voltage) from various sensors or transducers is input to the analog signal input device 1.

A multiplexer 11 receives the analog input signal.
The input signal 12 selected by (1) is amplified by the amplifier circuit 13 to the analog input voltage Vs50, and is converted into a digital signal via the conversion circuit 53 provided in the A / D converter 14. The converted digital output value Ys15 is stored in the memory 18 as the measured value Xs17 of each point by the CPU 16 inside the microcomputer 70. This measurement value is transmitted to the connected higher-level device 19.

The operation of the analog signal input device shown in FIG. 4 will be described with reference to FIG. FIG. 6 is a scaling diagram in a conventional analog signal input device. As shown in FIG. 6, the amplifying circuit 13a and the converting circuit 13b associate the full-scale value of the analog signal with the output signal from the transducer, and use the A / D converter 14 having a resolution of 10 bits (1023 division). In this case, it is theoretically configured so that when the lower limit full scale value is input, it is digitally converted to "0", and when the upper limit full scale value is input, it is digitally converted to "1023".

In an actual device, an error occurs in a digital output value due to the accuracy of each electronic component, and in order to correct an instrumental difference for each device, an upper limit adjusting variable resistor 20 and a lower limit adjusting variable resistor 21 are provided. They are used to make adjustments to approach the theoretical values. Further, a switching unit 30 for switching between the adjustment mode and the normal measurement mode is provided. Further, a display unit 40 as means for notifying the adjustment result to the outside is provided.

Next, software processing in a conventional example will be described. FIG. 5 is a PAD diagram in a conventional example. As shown in FIG. 5, in (S001), the adjustment / measurement switching unit of the switching unit 30 is confirmed, and the mode is set to the adjustment mode. (S0
In 02), the upper / lower limit switching unit of the switching unit 30 is further confirmed and switched to the lower limit adjustment mode, and the lower limit of the full scale value is adjusted. The following processing is performed in a state where the lower limit full scale value of the analog input signal is input to all points.

In (S011), 4 mA: 00 shown in FIG. 6 is used as an initial value of display information transmitted to the display unit 40.
The display information indicating the lower limit of 0H is set. (S
012), the A / D converter 1 for converting the input signal
4 is started, the input signal 12 is selected by the multiplexer 11 from the input signals 1 to n, fetched via the amplifier 13a, and A / D converted.

In (S013), C of the microcomputer 70
The digital signal that has been A / D-converted to PU 16 has an output value Y
Imported as s15. In (S014), the output value Ys15 taken in by the CPU 16 is set as a measured value. In (S015), it is determined whether or not the conversion value: digital signal Ys15 captured by the CPU 16 is larger than the lower limit allowable value.

In (S016), it is determined whether or not the converted value: digital signal Ys15 fetched by the CPU 16 is smaller than the lower limit allowable value. In (S017), this result is transmitted to the display unit 40 as display information. In this apparatus, only one system of adjustment circuit is provided for a plurality of input points, and the allowable range is given a width. If the measured values of all points fall within the allowable value, the adjustment is OK. If at least one of the points is out of the permissible value, an indication of adjustment NG is transmitted to the display unit 40. The lower limit is adjusted by using the lower limit adjusting variable resistor 21 so that an OK display is made while referring to the information from outside.

In (S021 to S027), similarly, the upper limit adjustment mode is set, and the upper limit is adjusted. (S0
In 31 to S033), after the upper and lower limits are adjusted in the adjustment mode, the mode is switched to the measurement mode, so that a normal measurement process is performed. A / D conversion is started for each analog input signal, and the output value is directly stored in the memory 18 as the measured value Xs.

Next, the details of the conventional A / D converter will be described. The A / D converter 14 shown in FIG.
With reference to the voltage Vcc51, the analog input voltage VS5
0 is converted into a digital output value YS15.
A conversion equation in the case of an A / D converter with a resolution of 10 bits (1023 divisions) is shown in the following equation (1).

(Equation 1) As shown in the above equation, that is, the accuracy of Vcc becomes the accuracy of the A / D converter, and a voltage VCC51 with good temperature stability is required.

Power supply AC10 of analog signal input device 1
From 0 V, a DC voltage Vcc 62 is generated via an AC / DC converter 60 and a DC / DC converter 61, and A
The / D converter 14 uses the DC voltage Vcc62 as the reference voltage Vcc51. The Vcc 51 is generally unstable with respect to a temperature change. However, a stabilizing circuit 54 is provided inside the A / D converter 14 so that the AVcc 52 having good temperature stability can be obtained.

Therefore, among the conversion errors from the input signal 12 to the digital output value Ys15, the error generated from the A / D converter is at a negligible level, and only the error generated from the amplifier circuit needs to be considered. This can be adjusted by the operation in the adjustment mode described above.

In the conventional example, the A / D converter 14 used is internally provided with a stable reference voltage AVcc 52
, The conversion accuracy is high,
In order to produce a stable reference voltage AVcc 52, a higher voltage Vcc is required, and therefore, the DC / DC
The circuit is complicated and the cost is high, for example, the DC converter 61 must be provided.

In order to solve the above-mentioned high cost, a general-purpose microcomputer may be used. A general-purpose microcomputer that has been widely used has a built-in A / D converter, eliminating the need for the external A / D converter and complicated circuits associated therewith.

Next, a case where this general-purpose microcomputer is used will be described. FIG. 7 is a block diagram of a conventional analog input signal device using a general-purpose microcomputer. The basic operation of the A / D conversion process of the analog signal input device 101 is the same as that of the external A / D converter of the analog signal input device 1 described with reference to FIG. Therefore, the description will be made with a focus on the characteristic points.

As shown, an input signal 112 selected by a multiplexer 111 is amplified by an amplifier circuit 113 to an analog input voltage 150. after that,
The signal is input to the A / D converter 114 in the microcomputer 170 and is converted into a digital signal via the conversion circuit 153. The converted digital output value 115Ys is
The memory 118 stores the measured value Xs 117 of each point at 116.
Is stored in This measurement value is stored in the upper
Transmitted to

The software processing in the analog input signal device using the general-purpose microcomputer shown in FIG.
It is omitted because it is equivalent to FIG. Next, the A / D converter 114 inside the general-purpose microcomputer of FIG. 7 will be described. The A / D converter 114 shown in FIG.
151 is directly connected to the reference voltage AVcc without a stabilizing circuit.
152. However, Vcc 151 is unstable with respect to a temperature change, and greatly affects the accuracy of the A / D converter.

[0019]

The above-mentioned general-purpose microcomputer has a built-in A / D converter, and does not require an external A / D converter and complicated circuits associated therewith. But,
The DC voltage generated from the power supply of the device via the AC / DC converter is taken in as the reference voltage of the A / D converter while being unstable to the temperature change.
This greatly affects the conversion accuracy of the A / D converter.

The conventional adjustment circuit using a variable resistor is a means for adjusting so as to eliminate an error caused by the accuracy of the electronic components, and cannot adjust an error due to a temperature change. The present invention has been made in order to solve the object of the related art, and has an analog signal input device, a method thereof, and a recording medium having improved stability of A / D conversion with stability against temperature change. Its purpose is to provide.

[0021]

To achieve the above object, an analog signal input device according to the present invention comprises an A / D converter for converting an analog input signal into a digital signal, and a microprocessor for controlling the A / D converter. An analog signal input device for outputting the digital signal to the outside, wherein the A / D converter has a first reference voltage serving as a reference for analog-to-digital conversion, and a second reference having temperature stability. And A / D of an analog input value based on a temperature change of the first reference voltage.
The conversion error is corrected by the microprocessor using an A / D conversion value of the second reference voltage as a specified voltage.

According to the present invention, there is provided an analog signal input method for converting an analog input signal into a digital signal and outputting the digital signal to an external device. And a second reference voltage having temperature stability, and converting an A / D conversion error of an analog input value based on a temperature change of the first reference voltage into an A / D conversion error of the second reference voltage.
The D-converted value is corrected as a specified voltage.

In the recording medium of the analog signal input method according to the present invention, the analog input signal is amplified and the A / D
A method for inputting an analog signal to be converted into a digital signal by a converter and output to the outside, wherein the amplified analog input voltage, a first reference voltage serving as a reference for A / D conversion, and temperature stability are provided. Inputting a second reference voltage to an A / D converter;
An analog signal comprising: a step of obtaining a correction coefficient based on a specified value after the / D conversion; and a step of multiplying the voltage value of the first reference voltage after the A / D conversion by the correction coefficient to obtain a measured value. A program that allows the computer to execute the above input method.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An analog signal input apparatus and method and a recording medium according to the present invention will be described. [Embodiment 1] Hereinafter, with reference to FIG. 1 to FIG.
An embodiment of an analog signal input device according to the present invention will be described. FIG. 1 is a block diagram of an embodiment of an input device used for an analog signal input method according to the present invention. In the analog signal input device according to the present invention, portions common to those of the conventional analog signal input device shown in FIG. 7 will not be described again because they are complicated, and the description will focus on the characteristic portions.

In FIG. 1, an input signal 212 is amplified to an analog input voltage Vs250 and
4 is converted to a digital output value Ys215 by the conversion circuit 253, and is similar to the processing of the conventional analog signal input device shown in FIG. I do.

In the present embodiment, the specified voltage Vref 282 is also input to the conversion circuit 253 in the A / D converter 214, like the analog input voltage Vs250 to be measured. The specified voltage Vref 282 has a low absolute value accuracy, but is stable with respect to a temperature change.
62 is formed by a shunt regulator 281 and the like having excellent temperature stability.

The specified voltage Vref 282 cannot be used as the reference voltage AVcc 252 because of its low potential.
The digital output value Ys215 to be measured is corrected by software processing using the D-converted specified output value Yref263, so that a measured value Xs217 stable against a temperature change can be obtained.

Next, the software processing of this embodiment will be described. FIG. 2 shows the PA of the analog signal input device of FIG.
D is a diagram, and FIG. 3 is a scaling diagram of the analog signal input device of FIG. The basic processing is the same as the PAD diagram of the conventional analog signal input device shown in FIG. 5, but is characterized in that a correction coefficient α is used.

First, the correction coefficient α and the measurement principle will be described. Now, in FIG. 1, the output signal value of the input signal Vs250 after AD conversion is represented by Ys215 and the specified voltage Vref28.
The output signal value after AD conversion of No. 2 is Yref 263, and the reference voltage is AVcc 252. Equation (1) Ys already described
= 1023 x Vs / AVcc, as the temperature changes, the unstable AVcc changes and Ys also changes.

[0030]

Yref = 1023 × Vref / AVcc (2) Now, the value of Yref “512” at AVcc = 5V
Based on

It is assumed that α = 512 / Yref (3) By substituting equation (2) into equation (3), the following equation (4) is obtained.

Α = 512/1023 × AVcc / Vref (4) Here, the expression (1) × (4) is calculated.

ΑYs = (512/1023) × (AVcc / Vref) × (1023 × Vs / AVcc) = (Vs / Vref) × 512 (5)

The above equation (5) is affected by the AVcc 252 which is unstable with respect to temperature when only Ys is used. However, the equation (5) is used except for the AVcc 252 by multiplying by α. According to the equation (5), the input signal Vs is 512 / Vr.
Since it is multiplied by ef, it must be multiplied by Vref / 512 before input to the A / D converter 214.

Next, the PAD processing and scaling of this embodiment will be described with reference to FIGS. PA in FIG.
The D processing is almost the same as the PAD processing in FIG.
The description of the common points will be omitted, and the description will focus on the differences. FIG.
The PAD processing according to the present embodiment shown in FIG.
As shown in 2), A / D conversion is started for the specified voltage, and the correction coefficient α is calculated from the specified output value as described above. The correction coefficient α is an operation coefficient for obtaining a stable measurement value with respect to the temperature coefficient, as described in detail above.

As shown in FIG. 5, in (S014),
While the lower limit is adjusted by using the output value Ys15 taken by the CPU 16 as the measured value, in FIG. 2 the output value Ys15 taken in by the CPU 16 is obtained in (S241, S242) from (S212) to (S217). The obtained value is multiplied by the obtained α.

Then, it is determined whether the measured value is smaller than the lower limit allowable value. The determination is made in a state where the lower limit full scale value of the analog input signal is input to all points, and the result is transmitted to the display unit 240.
Similarly, the mode is switched to the upper limit adjustment mode, and (S221 to S221)
At 227), the upper limit is adjusted similarly.

With the above adjustment operation, the absolute value error of the specified voltage can be absorbed. After adjusting the upper and lower limits in the adjustment mode, the normal measurement processing is performed by switching to the measurement mode. In the measurement mode, in (S261, S262), A / D conversion is started for the specified voltage, and the correction coefficient α is calculated from the specified output value.
Is calculated. In (S231 to S233), A / D conversion is started for each analog input signal, and a value obtained by multiplying the output value by a correction coefficient α is stored in the memory 218 as a measured value Xs. In this way, an accurate digital signal can be output for an analog input signal.

[Embodiment 2] Next, an embodiment of a recording medium according to the present invention will be described. In the recording medium according to the present invention, for example, P (floppy disk), ROM, R
An analog input signal is amplified using an AM or the like, converted into a digital signal by an A / D converter, and a second reference voltage having stable temperature characteristics is formed in an analog signal input method to be output to the outside; Inputting the amplified analog input voltage, a first reference voltage serving as a reference for A / D conversion, and the second reference voltage to an A / D converter; An analog comprising: a step of obtaining a correction coefficient based on a specified value after A / D conversion; and a step of multiplying the voltage value of the first reference voltage after A / D conversion by the correction coefficient to obtain a measured value. A program that allows a microcomputer to execute a signal input method is recorded so as to be readable by the microcomputer.

[0037]

As described above in detail, according to the analog signal input device and the method of the present invention, even if the reference voltage of the A / D converter fluctuates with temperature, the temperature stability can be improved. By inputting a good specified voltage to the A / D converter, it is possible to perform correction by software processing using the specified output value and obtain a measured value with good temperature stability. By doing so, the conventional adjustment circuit can be used as it is, and the power supply unit and the A / A
The circuit configuration of the D conversion unit can be further simplified. ADVANTAGE OF THE INVENTION According to the recording medium which concerns on this invention, the program by which the microcomputer can perform the input method of an analog signal can be recorded so that a microcomputer can read.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of an input device used for an analog signal input method according to the present invention.

FIG. 2 is a PAD diagram of the analog signal input device of FIG. 1;

FIG. 3 is a scaling diagram of the analog signal input device of FIG. 1;

FIG. 4 is a block diagram of a conventional analog signal input device.

FIG. 5 is a PAD diagram in a conventional example.

FIG. 6 is a scaling diagram of a conventional analog signal input device.

FIG. 7 is a block diagram of a conventional analog signal input device using a general-purpose microcomputer.

[Explanation of symbols]

1, 101, 201: analog signal input device 11, 111, 212 ... multiplexer 12, 112, 212 ... input signal 13, 113, 213 ... amplifier circuit 14, 114, 214 ... A / D converter 15, 115, 215 ... Digital output values YS 16, 116, 216 CPU 17, 117, 217 Measurement values XS 18, 118, 218 Memory 19, 119, 219 Host device 20, 21, 120, 121, 220, 221 Variable resistor 30, 130, 230 ... Switching unit 40, 140, 240 ... Display unit 50, 150, 250 ... Analog input voltage 51, 62, 151, 162, 251, 262, 280
... DC voltages Vcc 52, 152, 252 ... Reference voltages AVcc 53, 153, 253 ... conversion circuits 54 ... stabilization circuits 60, 160, 260 ... AC / DC converters 61 ... DC / DC converters 263 ... prescribed output values Yref 70, 170, 270: microcomputer 281: shunt regulator 282: specified voltage Vref

Claims (3)

[Claims] 253 1. An analog signal input device, comprising: an A / D converter for converting an analog input signal into a digital signal; and a microprocessor for controlling the A / D converter, wherein the A / D converter outputs the digital signal to the outside. Input a first reference voltage serving as a reference for analog-to-digital conversion and a second reference voltage having temperature stability, and perform an A / D conversion error of an analog input value based on a temperature change of the first reference voltage. Wherein the A / D conversion value of the second reference voltage is defined as a specified value by the microprocessor. 2. An analog signal input method for converting an analog input signal into a digital signal and outputting the digital signal to the outside, comprising a first reference voltage serving as a reference for analog-to-digital conversion, and a temperature stability. Using the second reference voltage, A / A of the analog input value based on the temperature fluctuation of the first reference voltage
An analog signal input method, wherein a D conversion error is corrected using an A / D conversion value of the second reference voltage as a specified value. 3. A method for inputting an analog signal, wherein an analog input signal is amplified, converted into a digital signal by an A / D converter, and output to the outside, wherein the amplified analog input voltage and a reference for A / D conversion are provided. A first reference voltage,
Inputting a second reference voltage having temperature stability to an A / D converter;
Obtaining a correction coefficient based on the specified value after the D conversion; and multiplying the voltage value after the A / D conversion of the first reference voltage by the correction coefficient to obtain a measured value. A recording medium characterized by recording a computer-readable program on which a computer can execute an input method. [0001]