JP2014160939A - Analog-digital conversion device and analog-digital conversion system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive analog-digital conversion device that can correct a temperature-induced drift in a detection value of detecting a quantity to be measured in a detection section without using an existing constant temperature device.SOLUTION: The analog-digital conversion device includes: a detection section 7 for outputting a digital version of an input quantity to be measured; first and second reference measured quantity generation sections 5, 6 for outputting different reference measured quantities within a measuring range accommodating an input/output value deviation of the detection section due to a change in an ambient temperature thereof, respectively, and inputting the respective outputs into the detection section so as not to temporally overlap the quantity to be measured; and a CPU 4 for computing a quantity to be measured which is prior to the deviation from a detection value of the quantity to be measured which is an output of the detection section on the basis of a detection value of the reference measured quantity generated by the first reference measured quantity generation section which is an output of the detection section and a detection value of the reference measured quantity generated by the second reference measured quantity generation section which is an output of the detection section, and outputting it as a detection value of the quantity to be measured which is prior to the deviation.

Description

  The present invention relates to an analog-digital conversion apparatus and an analog-digital conversion system for converting an analog measurement amount into a digitized measurement amount via a detection unit that performs amplification and A / D conversion.

In a conventional analog-to-digital converter, an analog voltage that is an analog measurement amount is amplified by an amplifier in a detection unit, digitized by an A / D converter, and a measurement amount (detection signal) is output. In order to eliminate the deviation (temperature-induced drift) of the output of the detector (detection signal) affected by changes in the ambient temperature of the detector (temperature-induced drift), a constant temperature device that keeps the ambient temperature of the detector constant is used. The device is attached to the detection unit, and the ambient temperature of the detection unit is set to a constant temperature, thereby suppressing changes in the ambient temperature of the detection unit and suppressing the deviation (temperature-induced drift).
Further, the present invention differs from the problem to be solved by the invention and the means for solving the problem, but Japanese Patent Laid-Open No. 63-233319 (Patent Document 1) individually detects each of a plurality of inputs. A detecting means provided with a section is disclosed.

JP-A-63-233319

Since the conventional analog-digital conversion device is configured as described above, a constant temperature device must be prepared, and the cost is high. Furthermore, it is necessary to mount a constant temperature device on the detection unit, and productivity is poor.
In the input means disclosed in Patent Document 1, since a detection unit is individually provided for each of a plurality of inputs, individual component differences in the detection unit remain. Removing the individual differences between the separate detection units is a complicated process in practice.

  The present invention has been made to solve the above-described problems, and corrects the temperature-induced drift in the detection value detected by the detection unit without using a temperature constant device as in the prior art. It is an object of the present invention to provide an inexpensive analog-to-digital conversion device and analog-to-digital conversion system that are capable of satisfying the requirements.

The analog-to-digital conversion device according to the present invention is a detection unit that digitizes and outputs an input measurement amount, and each of the detection units within a measurement range that allows for deviations between input and output values due to changes in ambient temperature of the detection unit. At least first and second reference measurement amount generation units that output different reference measurement amounts and are input to the detection unit so that each of the outputs does not overlap the measurement target amount in time, and the detection unit Based on a detection value of the reference measurement amount generated by the first reference measurement amount generation unit that is an output and a detection value of the reference measurement amount generated by the second reference measurement amount generation unit that is an output of the detection unit And a CPU that calculates the measured amount before the deviation occurs from the detected value of the measured amount that is the output of the detection unit and outputs the calculated measured value before the deviation occurs as a CPU. With things That.
The analog-to-digital conversion system according to the present invention includes a detection unit that digitizes and outputs an input measurement amount, and a measurement range that allows for deviation between input and output values due to changes in ambient temperature of the detection unit. Analog digital having at least first and second reference measurement amount generation units that output different reference measurement amounts and are input to the detection unit such that each output does not overlap the measurement amount in time A detection value of a reference measurement amount generated by the first reference measurement amount generation unit which is an output of the conversion device and the detection unit, and a reference generated by the second reference measurement amount generation unit which is an output of the detection unit The measured amount before the deviation occurs by calculating the measured amount before the deviation occurs from the detected value of the measured amount that is the output of the detection unit based on the detected value of the measured amount. Those having a CPU for outputting a detection value of the amount.

The present invention provides a detection unit that digitizes and outputs an input measurement amount, and outputs different reference measurement amounts within a measurement range that allows for deviations between input and output values due to changes in ambient temperature of the detection unit. Each of the outputs is at least first and second reference measurement amount generation units input to the detection unit so as not to temporally overlap the measurement amount, and the output of the detection unit. The output of the detection unit based on the detection value of the reference measurement amount generated by the reference measurement amount generation unit and the detection value of the reference measurement amount generated by the second reference measurement amount generation unit that is the output of the detection unit Since the CPU includes a CPU that calculates the measured amount before the deviation occurs from the detected value of the measured amount and outputs the detected value of the measured amount before the deviation occurs. Temperature control device The low-cost analog-to-digital conversion device that can correct the temperature-induced drift due to the ambient temperature change of the detection unit of the detection value detected by the detection unit without using the detection unit can be provided. By making one common detection unit for the quantity and each reference measurement amount generated by each of the first and second reference measurement amount generation units, there is an effect that the individual difference of the detection units can be reduced as much as possible.
The present invention also includes a detection unit that digitizes and outputs an input measured amount, and different reference measurements within a measurement range that allow for deviations between input and output values due to changes in the ambient temperature of the detection unit. An analog-to-digital conversion device having at least first and second reference measurement amount generation units that are input to the detection unit so that each output does not overlap with the measurement amount in terms of time, and A detection value of the reference measurement amount generated by the first reference measurement amount generation unit, which is an output of the detection unit, and a detection value of the reference measurement amount generated by the second reference measurement amount generation unit, which is an output of the detection unit. The CPU calculates the measured amount before the deviation occurs from the detected value of the measured amount, which is the output of the detection unit, and outputs it as the detected value of the measured amount before the deviation occurs Low-cost analog digital that can correct temperature-induced drift due to changes in ambient temperature of the detection value of the detected value detected by the detection unit without using a conventional temperature constant device. A conversion device can be provided, and the detection unit can be detected by making the detection unit a single detection unit common to the measured amount and the respective reference measurement amounts generated by the first and second reference measurement amount generation units. There is an effect that the individual difference of the part can be reduced as much as possible.

It is a figure which shows Embodiment 1 of this invention, and is a block diagram which shows an example of a structure of an analog-digital converter. It is a figure which shows Embodiment 1 of this invention, and is explanatory drawing of the characteristic of the detected value with respect to a measured amount, and the concept of Embodiment 1. FIG. It is a figure which shows Embodiment 1 of this invention, and is operation | movement explanatory drawing which illustrates operation | movement with a flowchart. It is a figure which shows Embodiment 2 of this invention, and is operation | movement explanatory drawing illustrated with a flowchart. It is a figure which shows Embodiment 3 of this invention, and is a block diagram which shows the other example of a structure of an analog digital converter. It is a figure which shows Embodiment 3 of this invention, and is explanatory drawing of the characteristic of the detected value with respect to a measured amount, and the concept of Embodiment 2. FIG. It is a figure which shows Embodiment 3 of this invention, and is operation | movement explanatory drawing illustrated with a flowchart. It is a figure which shows Embodiment 4 of this invention, and is a block diagram which shows the further another example of a structure of an analog digital converter. It is a figure which shows Embodiment 4 of this invention, and is explanatory drawing of the characteristic of the detected value with respect to a measured amount, and the concept of Embodiment 4. FIG. It is a figure which shows Embodiment 4 of this invention, and is operation | movement explanatory drawing illustrated with a flowchart.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an example of the configuration of the analog-digital conversion apparatus according to the present embodiment, FIG. 2 is an explanatory diagram of the characteristics of the detected value with respect to the measured quantity and the concept of the present embodiment, and FIG. It is operation | movement explanatory drawing which illustrates operation | movement with a flowchart.

In FIG. 1, the analog-to-digital converter of this embodiment includes a changeover switch 1, an amplifier 2 for amplifying an analog input signal (amount to be measured), and an A / D converter 3, an A / D converter. CPU 4 to which a signal digitized by the device 3 is inputted, a first reference measurement amount generator 5 for generating a first reference measurement amount A within the measurement range, and the first reference measurement amount within the measurement range A second reference measurement amount generator 6 that generates a larger second reference measurement amount B, and a storage device 8 (hereinafter referred to as a RAM) that is a volatile storage device that temporarily stores data used for calculation in the CPU 4 RAM8).

The CPU 4 switches the selector switch 1 to select at least two reference measurement amounts A and B, and acquires a correction signal for correcting the temperature-induced drift in the detection unit 7 of the output of the detection unit 7. In the present embodiment, there are two reference measurement amounts (A, B), which are values near the minimum value and near the maximum value of the analog input span (measurement range for measuring the measured amount).
The CPU 4 stores data used for calculation in the CPU 4 described later in the RAM 8. Further, the CPU 4 transmits the measurement amount data X after correcting the temperature-induced drift to the host device 9 such as a monitoring device, a control device, or a monitoring control device.

1 will be described with reference to FIGS. 2 and 3. FIG.
First, as a premise, the temperature change gradually changes in time compared with the measurement frequency.

In FIG. 2, the horizontal axis represents a measured amount X such as an analog voltage value, and the vertical axis represents a detection value (digital value) Y that is an output of the A / D converter 3. It is assumed that the detection values corresponding to the reference measurement amounts A and B are A0 and B0 as design reference values. This value represents a detected value and a point on this coordinate plane. That is, the characteristic diagram of the detected value corresponding to the measured quantity is a straight line L0 connecting the points A0 and B0 as a design standard.
In this case, the span (measurement range) is represented by S0 (B0-A0). It is assumed that this characteristic diagram has actually changed to a straight line L1 due to the ambient temperature change. That is, the detection values corresponding to the reference measurement amounts A and B are A1 (= A0 + a) and B1 (= B0 + b). For example, the ambient temperature of the design reference straight line L0 is 20 ° C., and the ambient temperature of the temperature-induced drift L1 is 50 ° C.

The detected value corresponding to a certain measurement amount X is the ordinate Y0 of the point P according to the characteristics of the straight line L0, and the ordinate Y1 of the point Q according to the characteristics of the straight line L1.
On the contrary, if the detected value Y1 is input, the corresponding measurement amount is the abscissa X of the point Q according to the characteristics of the straight line L1, and the abscissa Xe of the point P0 according to the characteristics of the straight line L0. It becomes.

  In the case of a conventional device that does not have the function of detecting the reference measurement amounts A and B, the original detection value for the measurement amount X is Y0, but the value Y1 is input due to the ambient temperature change of the detection unit 7. Will do. That is, the detection value Y1 is erroneously detected as the measurement amount Xe, which should be the measurement amount X.

If there is a function to detect the reference measurement amounts A and B, the reference measurement amounts A and B can be acquired, so the CPU 4 calculates the straight line L1 and corrects the detection value Y1 with the measurement amount X. be able to.
Obtaining a correct measurement amount X with respect to the detection value Y1 is “temperature-induced drift correction of the measurement amount detector”.
Therefore, the temperature-induced drift correction of the measurement amount detection unit is correct by obtaining the reference measurement amounts A and B and each detection amount of the measurement amount (the output of the detection unit 7 (digitized output)) and performing a correction calculation. Take the process of calculating back the measured quantity.

Digital outputs A1, B1, and Y from the detection unit 7 for the reference measurement amounts A and B and the actual measurement amount (measurement amount) are input to the CPU 4 at certain intervals, and the actual measurement amount X is calculated by the CPU 4. In the present embodiment, the reference measurement amount A selects the minimum value of the measurement range, and the reference measurement amount B selects the maximum value of the measurement range.
In the case of calculation formula, equation of straight line L1
Y = A1 + (B1-A1) (X-XA) / (XB-XA)
Where Y = Y1
X = XA + (XB-XA) (Y1-A1) / (B1-A1)
Get.

  The operation when the CPU 4 takes the above process will be described with reference to FIG.

In FIG. 3, first, in steps S1 to S3, the detected values (outputs of the detection unit 7 (digitized output)) A1, B1, and Y of the reference measured amounts A and B and the actual input measured amount (measured amount) are set. Input to CPU4. Since the detected values A1, B1, and Y of the reference measured quantities A and B and the actual input measured quantities (measured quantities) cannot be input to the CPU 4 at the same time,
Input to the CPU 4 step by step. Here, the input order of S1 to S3 does not matter. Also, since the input calculation data is temporarily stored, the data (digital values of A1, B1, and Y after A / D conversion) is stored in the RAM 8 which is a temporary storage device when the step is shifted. To do. In step S4, A1, B1, and Y are read from the RAM 8, and the next calculation is performed in step S5.
X = XA + (XB-XA) (Y-A1) / (B1-A1)
In step S6, the obtained measurement amount X is output, and the same is repeated in the same manner at a constant cycle.

Now, since the processing time in the microprocessor is generally faster than the time when the ambient temperature changes, the temperature does not change significantly during the period from A1 to B1 acquisition. Therefore, as long as the process of FIG. 3 is performed at a constant period, the temperature-induced drift of the output of the detection unit 7 due to the ambient temperature change of the detection unit 7 is corrected. In addition, a feature of the present invention is that the reference measurement amount is made the same as the measurement amount by the detection unit 7 (amplifier circuit 2 and A / D converter 3) in which the measurement amount is processed. The temperature-induced drift in the measurement amount detection unit 7 can be corrected. Further, the temperature-induced drift caused by the ambient temperature change can be automatically corrected by the CPU.
As described above, according to the present embodiment, it is not necessary to use a constant temperature device, and it is not necessary to attach the constant temperature device to the detection unit. It is possible to realize an analog-to-digital conversion apparatus that can reduce the temperature-induced drift of the detection value in the detection unit.
In addition, as in Patent Document 1, when a detection unit is individually provided for each of a plurality of inputs, individual component differences of the detection unit remain. Removing the individual differences between the separate detection units is a complicated process in practice. On the other hand, in the first embodiment, a single detection unit common to the measured amount and the respective reference measurement amounts generated by the first and second reference measurement amount generation units, Individual differences in the detection unit can be reduced as much as possible.
Therefore, according to the first embodiment, not only the individual difference of the detection units can be made as small as possible, but also drift due to temperature can be corrected, and an analog-digital conversion device, analog that is highly reliable with respect to changes in ambient temperature, and analog A digital conversion system can be provided.

Embodiment 2. FIG.
In Embodiment 1, in the operation of FIG. 3, for each correction of the temperature-induced drift in a short time, the detected values of the reference measurement amounts A and B (digital outputs of the detection unit 7) A1 and B1 that are correction reference signals Since the capture is performed every time in the processes of steps S1 and S2, the reference measurement amounts A and B are frequently selected with the changeover switch 1. In addition, during the period in which the two reference measured amounts A and B are selected, the measured amount (analog input in FIG. 1) cannot be selected and input. Actually, since the reference measurement amounts A and B are constant, they do not change compared to the measurement amount. Further, the ambient temperature change is gradual in time, and it is not necessary to frequently measure the reference measurement amounts A and B at the reference point that changes only with temperature.
For this reason, in the second embodiment, the measurement frequency of the reference measurement quantities A and B such as the reference voltage is reduced, and the measurement frequency of the measurement quantity that is an analog quantity is increased, whereby the measurement quantity can be measured more accurately in real time. The operation of the CPU 4 of this embodiment will be described below with reference to the flowchart of FIG.

First, in step S11, a Y value is input. In step S12, it is determined whether to proceed to step S13 for inputting the reference measurement amount detection values A1 and B1 or step S15 for not inputting the reference measurement amount detection values A1 and B1, according to the number of times of Y input. If N is an odd number starting from 3, for example (N = 3, 5,... N), the number of times A1 and B1 are input can be thinned out once.
Steps after step S16 are the same as those after step S5 in FIG.
By the above operation, it is possible to select the number of times of input of the detected values A1 and B1 of the reference measured amount, that is, by specifying the function of N, the number of times of input of the detected values A1 and B1 of the reference measured amount to the CPU is minimized. It can be reduced, and the accuracy of the measurement amount for the correction can be increased.

Embodiment 3 FIG.
As another example of the first embodiment, the accuracy of correcting the temperature-induced drift of the output of the detection unit 7 can be improved by increasing the reference measurement points from two points. In the first embodiment, the reference is set to two points A1 and B1, and the temperature-induced drift of the detection unit is corrected. However, in the third embodiment, a reference measurement amount C1 such as a reference voltage is added as shown in FIG. Thus, the accuracy for correction is improved, and the third embodiment will be described below with reference to FIGS.
FIG. 5 is a block diagram showing an example of the third embodiment in which three reference points are used. The only difference from FIG. 1 is the addition of a third reference measurement amount generator 10 that generates a reference measurement amount C1. In the present embodiment, the relationship between the magnitudes of the reference measurement amounts A1, B1, and C1 is A1 <C1 <B1.

FIG. 6 shows a characteristic diagram when three reference points, which are an example of the third embodiment, and FIG. 7 shows an operation flowchart of the CPU 4 when three reference points, which are an example of the third embodiment.
The operation of the CPU 4 having the characteristics of FIG. 6 will be described with reference to the flowchart of FIG.
In steps S21 to S24, the detected values A1, B1, and C1 of the reference measured amounts A, B, and C and the detected value Y of the measured amount are input. In step S25, the detected value Y of the measured amount is changed to the reference measured amount A, It is determined which straight line portion of the straight line connecting the detected values A1, B1, and C1 of B and C is present. That is, in step S25, it is determined whether or not the detected value Y of the measured amount is less than the detected value C1 of the reference measured amount.If YES, the straight line portion L0 connecting the detected value A1 of the reference measured amount and the detected value C1 of the reference measured amount I understand that there is. Accordingly, in step S26, the detected values A1 and C1 of the reference measurement amounts A and C corresponding to the start point and end point of the straight line portion are read from the RAM 8, and calculation (1) is performed in step S27. This calculation (1) is in accordance with step S5 in FIG.

  If NO in step S25, it is known that the line portion L1 connects the detection value C1 of the reference measurement amount C and the detection value B1 of the reference measurement amount B. The reference measurement amounts C1 and B1 to be read are read from the RAM 8, and calculation (2) is performed in step S29. This calculation (2) is in accordance with step S5 of FIG. In step S30, the measurement amount X to be obtained, which is the result of each of the calculations (1) and (2), is output, and the same is repeated thereafter.

  In the third embodiment, if the reference point can be increased to infinity instead of three points, all the straight lines for correction can be represented by points, and theoretically, the temperature at the detection unit 7 to the output of the detection unit 7 can be expressed. The influence of the caused drift can be eliminated.

Embodiment 4 FIG.
In general, an analog-to-digital conversion apparatus is equipped with a volume resistor for adjusting an analog quantity to adjust the initial error in order to adjust variation (initial error) in characteristics of an amplifier and an A / D converter. Specifically, the measured value corresponding to the zero point (minimum point of the measurement range) and span point (maximum point of the measurement range) is simulated as an analog input, and the digital value in the case of the simulated input corresponding to the zero point is zero. Adjust to the design value at the point, then input a simulated input corresponding to the span point, and adjust the volume to the design value at the span point. In this case, the volume resistance of the zero point and the span point is the same, and it is necessary to adjust the zero point and the span point a plurality of times, and adjustment takes time.

The fourth embodiment exemplifies a device having a temperature-induced drift correction function in consideration of the variation (initial error) in the above characteristics, and this embodiment will be described below with reference to FIGS. 8 to 10. .
FIG. 8 is an apparatus configuration diagram when an example of the fourth embodiment is applied. Compared with FIG. 1 of the first embodiment, a nonvolatile storage device 11 such as an EEPROM is added. In addition, a determination signal can be input from the host controller 9 in order to determine whether or not to perform an initial error adjustment calculation. The EEPROM 11 stores data for correcting characteristic variation (initial error).

FIG. 9 shows a characteristic diagram, and shows a characteristic diagram when correcting the variation (initial error) of the characteristic and a characteristic diagram when correcting the temperature-induced drift.
The following description will be made assuming that the variation in the characteristics of the detection unit 7 is much larger than the variation in the detected values A1 and B1 of the reference measurement amounts A and B.
In FIG. 9, similarly to FIG. 2 of the first embodiment, the measurement amount (analog value) is taken on the horizontal axis, and the detection amount (digital value that is the output of the detection unit 7) is taken on the vertical axis. Assume that the signals corresponding to the two reference values Xa and Xb of the measured quantity are A0 and B0 as design reference values. In this case, a straight line L0 passing through two points A0 and B0 is a design reference straight line.

  For example, if the design standard is an ambient temperature of 25 ° C, enter the measurement quantity reference Xa (minimum value of the measurement range) and Xb (maximum value of the measurement range) while the ambient temperature of the device is actually 25 ° C. Assume that the output values of the detectors 7 are A1 and B1, and a straight line passing through these two points A1 and B1 is a straight line L1. The deviation amounts of the straight line L1 at the minimum and maximum points of the measurement range due to the variation in characteristics from the design criteria A0 and B0 are represented by a (= A1−A0) and b (= B1−B0), respectively.

When the reference XA and XB are input at a certain ambient temperature, and the detected values are A2 and B2, respectively, the deviation amount due to characteristic variation is based on the straight line L2 at A3 and B3 with a and b taken into account. By performing the calculation for correcting the temperature-induced drift, it is possible to measure the correct measurement amount by the temperature-induced drift correction in consideration of the characteristic variation. Therefore, for temperature-induced drift correction in consideration of characteristic variations, (1) “obtain correction amounts a and b” and (2) “reference measurement amounts A and B and measurement amount Y are obtained and correction calculation is performed. , Do two steps to back-calculate the correct measurement.

  (1) For “obtaining correction amounts a and b”, obtain reference detection values A1 and B1 due to variations in characteristics with respect to design values A0 and B0 with ambient temperature as the design reference. Deviations a and b due to characteristic variations are obtained. For standards A and B, the minimum and maximum values of the measured quantity are entered.

(2) For “obtaining the reference measurement amounts A and B and the measured amount Y and performing the correction calculation”, A3, where the deviation amounts a and b are added to the points A2 and B2, A measurement amount X corresponding to the measurement signal Y is obtained on the straight line L2 connecting B3. Also, by calculation,
Equation for the straight line L2 y = A3 + (B3−A3) (x−XA) / (XB−XA)
X = XA + (XB−XA) (Y−A3) / (B3−A3)
Get.

The operation when the CPU 4 takes the above process is mainly shown in the flowchart of FIG.
Description will be made with reference to FIGS.
In FIG. 10, after the start, first, in step S31, it is determined whether or not there is an operation command T for determining a correction amount due to characteristic variation. That is, if there is a correction data fetch command T from the host device 9, 1 is taken if 1 is not taken. This command T is only given at the time of adjustment on the producer side and on the regular inspection and adjustment after repair on the user side. If YES, that is, if the command T is 1, the process proceeds to step S32. If NO, that is, if the command T is 0, the process proceeds to step S37.

In steps S32 to S36, the reference detection values A1 and B1 resulting from the characteristic variation with respect to the design values A0 and B0 are obtained with the ambient temperature corresponding to the above (1) as the design standard, and the characteristic variation Deviation amounts a and b are obtained.
In step S33, A1 including the characteristic variation of the detection unit 7 is input, and in step S33, the characteristic variation deviation amount a is calculated and obtained. Subsequently, B1 including the characteristic variation is input in step S34, and b which is the characteristic variation deviation amount is calculated in step S35. In step S36, the deviation amounts a and b are stored in the EEPROM 11 which is a deviation amount storage device. The steps so far correspond to the above-mentioned (1).

The following is the step (2) described above. Steps S37 to S39 conform to the operations of S4 to S6 in FIG. 3, and the CPU 4 inputs the reference measured amounts A and B and the detected values A2, B2, and Y of the measured amounts, respectively, and temporarily stores them. It is stored in the RAM 8, which is a device. In step S40, the detection values A2, B2, and Y corresponding to the deviation amounts a and b and the actual measurement amount are read from the storage device.
Thus, the preparation for correction calculation is completed, and the next calculation is performed in step S41.
X = XA + (XB-XA) (Y-A3) / (B3-A3)
[X = XA + (XB−XA) {Y− (A2−a)} / {(B2−b) − (A2−a)}]
In step S42, the obtained measurement quantity X is output and repeated in a constant cycle.

  According to the fourth embodiment, the volume resistance mounted on the amplifier circuit can be eliminated, and not only the cost can be reduced, but also the adjustment can be performed automatically, so that the adjustment time can be shortened.

As described above, in each of the first to fourth embodiments, the first reference measurement amount generating unit that generates the first reference measurement amount within the measurement range without using a conventional temperature constant device. Inexpensive analog capable of automatically correcting temperature-induced drift using a CPU and a second reference measurement amount generator that generates a second reference measurement amount that is larger than the first reference measurement amount within the measurement range A digital conversion device can be provided.

  In other words, any of the first to fourth embodiments eliminates the temperature constant device as in the prior art and eliminates the influence of temperature-induced drift of the amplification circuit and A / D converter in the detection unit. Two reference voltage generators, a changeover switch, a CPU, and a RAM that is a storage device are provided, and correction is performed by the CPU. The CPU inputs two reference and digital values of the amount to be measured with the changeover switch. Since it is not possible to select two criteria and a measured quantity at the same time, input data is stored in a temporary storage device. The two reference digital values are values including deviation amounts due to the temperatures of the amplification circuit and the A / D converter in the detection unit. Since the signal under measurement is also converted into a digital value by the same amplifier circuit and A / D converter circuit, it is on a straight line connecting these two reference points. According to the straight line connecting the two reference points, the analog quantity to be measured is back-calculated from the digital quantity to be measured, so that the detection section can detect the change in the ambient temperature of the detection section having the amplifier and the A / D converter. This corrects the temperature-induced drift of the measured quantity and obtains the correct measured quantity.

  In general, the host device 9 often has a CPU and a storage device such as a monitoring device and a control device. For this reason, in any of the first to fourth embodiments, an analog-to-digital conversion system in which the above-described temperature-induced drift correction calculation is performed by a CPU such as the host apparatus 9 can be provided.

The aforementioned first to fourth embodiments have the following features 1 to 4, for example.
Feature 1: In an analog-to-digital converter or analog-to-digital conversion system that amplifies a minute analog voltage by an amplifier in a detection unit and obtains a digitized value by an A / D converter, the amplifier and the A / D In order to correct changes in characteristics due to changes in the ambient temperature of the D converter, two reference voltage generators, a changeover switch, a CPU, and a RAM, which is a volatile storage device, are provided in the same device, and two reference voltages and a measurement target The input voltage is measured by alternating digital conversion, and the analog voltage of the voltage to be measured is back-calculated on the basis of a straight line connecting two reference voltage values by the CPU in the same device, so that the amplifier and the A / D converter An analog-to-digital converter or analog-to-digital converter that corrects deviations from ambient temperature changes (temperature-induced drift) to obtain the correct measurement It is a stem.
Feature 2: In the device or system of Feature 1, when the two reference voltage values are selected and input with the changeover switch, the number of times the voltage to be measured is the original measurement target by thinning out the number of times of selection of the reference voltage, that is, the number of times of input. Therefore, the present invention is an analog-to-digital conversion device or an analog-to-digital conversion system that can obtain an accurate analog voltage in real time.
Feature 3: In the device or system of Feature 1, analog-to-digital conversion that improves the accuracy by increasing the resolution with respect to the variation with respect to the ambient temperature by adding the number of reference voltage values, and obtains the correct measurement amount Device or analog-to-digital conversion system.
Feature 4: Analog-to-digital conversion in which the device or system of Feature 1 is provided with an EEPROM, which is a non-volatile storage device, so as to obtain a correct measurement amount in consideration of variations (initial errors) inherent to the amplifier and the A / D converter Device or analog-to-digital conversion system.

Also, from a different viewpoint, the first to fourth embodiments described above have, for example, the following features 1 to 10 as a superordinate concept.
Feature as a superordinate concept 1: A detection unit that digitizes and outputs an input measured amount, and different reference measurements within a measurement range that allow for deviations between input and output values due to changes in ambient temperature of the detection unit. Output of the at least first and second reference measurement amount generation units input to the detection unit so that each output does not overlap the measurement target in time, and the output of the detection unit The detection based on a detection value of the reference measurement amount generated by the first reference measurement amount generation unit and a detection value of the reference measurement amount generated by the second reference measurement amount generation unit, which is an output of the detection unit. Analog-to-digital conversion provided with a CPU that calculates the measured quantity before the deviation occurs from the detected value of the measured quantity, which is an output of the unit, and outputs it as the detected value of the measured quantity before the deviation occurs apparatus A.
Feature 2 as a superordinate concept: In the analog-to-digital conversion device according to feature 1 as a superordinate concept, the detected value of the measured amount by the detection unit, and the reference measurement amount generated by the first reference measurement amount generation unit Both of the detection value of the detection unit and the detection value of the reference measurement amount generated by the second reference measurement amount generation unit by the detection unit are written in a storage device and written to the storage device The detected value of the measured amount, the detected value of the reference measured amount generated by the first reference measured amount generating unit, and the detected value of the reference measured amount generated by the second reference measured amount generating unit, An analog-to-digital converter that the CPU reads out from the storage device, calculates the measured amount before the deviation occurs, and outputs it as a detected value of the measured amount before the deviation occurs It is.
Feature 3 as a superordinate concept: In the analog-to-digital conversion device according to the feature 1 or 2 as a superordinate concept, the detected value of the reference measurement amount generated by the first reference measurement amount generation unit and the second reference measurement amount The CPU calculates the measured amount before the deviation occurs from a value corresponding to the detected value of the measured amount on a line connecting the detected value of the reference measured amount generated by the generating unit, and It is an analog-digital converter that outputs as a detected value of the measured amount before a deviation occurs.
Feature 4 as a superordinate concept: In the analog-digital conversion device according to feature 2 as a superordinate concept, the number of times the detected value of the measured amount is written to the storage device by the detection unit is the first and second The CPU generates the first and second reference measurement amount generation units so that the detected value of each reference measurement amount generated by the reference measurement amount generation unit exceeds the number of times the detected value is written to the storage device. It is an analog-digital conversion device that performs a process of restricting writing of the detected value of each reference measurement amount to the storage device.
Feature 5 as a superordinate concept: In the analog-to-digital conversion device according to any one of features 1 to 4 as a superordinate concept, each of the reference measurement amounts generated by the first and second reference measurement amount generation units is Is an analog-digital converter having a size that takes into account the initial error inherent to the detector.
Feature 6 as a superordinate concept: A detection unit that digitizes and outputs an input measured quantity, and different reference measurements within a measurement range that allow for deviations between input and output values due to changes in ambient temperature of the detection unit. An analog-to-digital conversion device having at least first and second reference measurement amount generation units that are input to the detection unit so that each output does not overlap with the measurement amount in terms of time, and A detection value of the reference measurement amount generated by the first reference measurement amount generation unit, which is an output of the detection unit, and a detection value of the reference measurement amount generated by the second reference measurement amount generation unit, which is an output of the detection unit. And calculating the measured quantity before the deviation occurs from the detected value of the measured quantity, which is the output of the detection unit, and outputting it as the detected value of the measured quantity before the deviation occurs C An analog-digital conversion system comprising a U.
Feature 7 as a superordinate concept: In the analog-to-digital conversion system according to feature 6 as a superordinate concept, the detected value of the measured amount by the detection unit, and the reference measurement amount generated by the first reference measurement amount generation unit Both of the detection value of the detection unit and the detection value of the reference measurement amount generated by the second reference measurement amount generation unit by the detection unit are written in a storage device and written to the storage device The detected value of the measured amount, the detected value of the reference measured amount generated by the first reference measured amount generating unit, and the detected value of the reference measured amount generated by the second reference measured amount generating unit, The CPU reads from the storage device, the CPU calculates the measured amount before the deviation occurs, and outputs it as a detected value of the measured amount before the deviation occurs. A log-to-digital conversion system.
Feature 8 as a superordinate concept: In the analog-to-digital conversion system according to feature 6 or 7 as a superordinate concept, the detected value of the reference measurement amount generated by the first reference measurement amount generation unit and the second reference measurement amount The CPU calculates the measured amount before the deviation occurs from a value corresponding to the detected value of the measured amount on a line connecting the detected value of the reference measured amount generated by the generating unit, and An analog-to-digital conversion system that outputs as a detected value of the measured amount before a deviation occurs.
Feature 9 as a superordinate concept: In the analog-to-digital conversion system according to feature 7 as a superordinate concept, the number of times the detected value of the measured amount is written to the storage device by the detection unit is the first and second The CPU generates the first and second reference measurement amount generation units so that the detected value of each reference measurement amount generated by the reference measurement amount generation unit exceeds the number of times the detected value is written to the storage device. An analog-to-digital conversion system that performs a process of restricting writing of the detected value of each reference measurement amount to the storage device.
Feature 10 as superordinate concept: In the analog-to-digital conversion system according to any one of features 6 to 9 as superordinate concept, each of the reference measurement amounts generated by the first and second reference measurement amount generating units is The analog-to-digital conversion system is characterized in that it has a size that takes into account the initial error inherent to the detection unit.

In the present invention, each embodiment can be appropriately modified or omitted within the scope of the invention.
In addition, in each figure, the same code | symbol shows the same or an equivalent part.

1 selector switch, 2 amplifier circuit, 3 A / D converter,
4 CPU, 5 1st reference measurement amount generation part, 6 2nd reference measurement amount generation part,
7 detection unit, 8 RAM (storage device), 9 host device,
10 Third reference measurement amount generation unit, 11 EEPROM (storage device).

Claims (10)

A detector that digitizes and outputs the input measured amount,
Different reference measurement amounts within a measurement range that allow for deviations between input and output values due to changes in the ambient temperature of the detection unit are output so that each of the outputs does not overlap the measured amount in time. At least first and second reference measurement amount generation units input to the detection unit, and a detection value of the reference measurement amount generated by the first reference measurement amount generation unit that is an output of the detection unit and the detection unit And the measured value before the deviation occurs from the detected value of the measured amount that is the output of the detecting unit based on the detected value of the reference measured value generated by the second reference measured value generating unit that is the output of CPU that calculates a quantity and outputs it as a detected value of the measured quantity before the deviation occurs
An analog-to-digital converter with The analog-to-digital converter according to claim 1,
The detection value of the measured amount by the detection unit, the detection value of the reference measurement amount generated by the first reference measurement amount generation unit, and the second reference measurement amount generation unit generated by the detection unit Any of the detected values by the detection unit of the reference measurement amount is written in the storage device,
The detected value of the measured amount written in the storage device, the detected value of the reference measured amount generated by the first reference measured amount generating unit, and the reference generated by the second reference measured amount generating unit The detected value of the measured amount is read from the storage device by the CPU, and the CPU calculates the measured amount before the deviation occurs and outputs it as the detected value of the measured amount before the deviation occurs. An analog-to-digital conversion device characterized by: The analog-to-digital converter according to claim 1 or 2,
The measured amount on the line connecting the detected value of the reference measured amount generated by the first reference measured amount generating unit and the detected value of the reference measured amount generated by the second reference measured amount generating unit. An analog-to-digital converter characterized in that the CPU calculates the measured amount before the deviation occurs from a value corresponding to a detected value, and outputs it as a detected value of the measured amount before the deviation occurs . The analog-digital converter according to claim 2,
The number of times the detected value is written to the storage device by the detection unit is the number of times the first and second reference measurement amount generation units generate the detected value of the reference measurement amount to the storage device. The CPU performs a process of restricting writing of the detected values of the respective reference measurement amounts generated by the first and second reference measurement amount generation units to the storage device so that the number of times of writing is greater than An analog-to-digital converter characterized by In the analog-digital converter as described in any one of Claims 1-4,
Each of the reference measurement amounts generated by the first and second reference measurement amount generation units has a size that takes into account an initial error specific to the detection unit. A detection unit that digitizes and outputs an input measurement amount, and outputs different reference measurement amounts within a measurement range that allow for deviations between input and output values due to changes in ambient temperature of the detection unit. An analog-to-digital conversion device having at least first and second reference measurement amount generation units that are input to the detection unit so that the output does not overlap the measurement target in time, and an output of the detection unit The detection based on a detection value of the reference measurement amount generated by the first reference measurement amount generation unit and a detection value of the reference measurement amount generated by the second reference measurement amount generation unit, which is an output of the detection unit. CPU that calculates the measured amount before the deviation occurs from the detected value of the measured amount that is an output of the unit and outputs the calculated value as the detected value of the measured amount before the deviation occurs
Analog-digital conversion system equipped with. The analog-to-digital conversion system according to claim 6,
The detection value of the measured amount by the detection unit, the detection value of the reference measurement amount generated by the first reference measurement amount generation unit, and the second reference measurement amount generation unit generated by the detection unit Any of the detected values by the detection unit of the reference measurement amount is written in the storage device,
The detected value of the measured amount written in the storage device, the detected value of the reference measured amount generated by the first reference measured amount generating unit, and the reference generated by the second reference measured amount generating unit The detected value of the measured amount is read from the storage device by the CPU, and the CPU calculates the measured amount before the deviation occurs and outputs it as the detected value of the measured amount before the deviation occurs. An analog-digital conversion system characterized by The analog-digital conversion system according to claim 6 or 7,
The measured amount on the line connecting the detected value of the reference measured amount generated by the first reference measured amount generating unit and the detected value of the reference measured amount generated by the second reference measured amount generating unit. An analog-to-digital conversion system, wherein the CPU calculates the measured amount before the deviation occurs from a value corresponding to a detected value, and outputs the measured value before the deviation occurs as a detected value of the measured amount before the deviation occurs . The analog-to-digital conversion system according to claim 7,
The number of times the detected value is written to the storage device by the detection unit is the number of times the first and second reference measurement amount generation units generate the detected value of the reference measurement amount to the storage device. The CPU performs a process of restricting writing of the detected values of the respective reference measurement amounts generated by the first and second reference measurement amount generation units to the storage device so that the number of times of writing is greater than An analog-to-digital conversion system. The analog-to-digital conversion system according to any one of claims 6 to 9,
Each of the reference measurement amounts generated by the first and second reference measurement amount generation units has a size that takes into account an initial error specific to the detection unit.