JPS62114332A - Analog-digital converting system - Google Patents

Abstract

PURPOSE:To subject outputs of various measures to A/D conversion with one converter by linearizing A/D-converted measured quantities on a basis of measured quantities of individual measures with a prescribed output of the A/D converter as a reference value. CONSTITUTION:Temperature measured values X1, X2,... from various thermocouples pass amplifiers 71-7n, whose gains are so adjusted that 100% of digital converted values is a prescribed reference value, and a multiplexer 6 and are subjected to A/D conversion by an A/D converter 5 and are written in a common memory 3 through a local CPU 4. Contents of the memory 3 are linearized and corrected in accordance with a correction table by a host CPU 1 and are outputted. Thermocouple-classified information due to a temperature resistor 8 is supplied to the multiplexer 6, and the CPU 1 selects the incorporated correction table for linearization on a basis of this information. Thus, measured values of various kinds of thermocouple or the like are processed by one A/D converter and are linearized and corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention converts thermoelectromotive voltage (analog amount) output from a thermocouple as a thermometer into an analog/digital (A/D)
) This relates to an analog-to-digital conversion method in which, after converting to obtain a digital quantity, this is subjected to linearization processing to linearize the non-linear characteristics of the thermocouple by a broken line approximation, and then output.

[Conventional technology]

FIG. 1 is a block diagram that shows the hardware configuration of an embodiment of the present invention and can also be used to explain the prior art.

In the figure, CPU (Central Processing Unit 1)
, 21d has:r/controller, 3 is common memory, 4 is local CPU, 5 is A/D conversion circuit, 6 is multiplexer, 71 to 7n are amplifiers, AFi address bus, C is control bus, D is data bus ,K
11 and 2 are semiconductor switches, and X1 to Xn are inputs (for example, thermoelectromotive voltages from thermocouples).

In Figure 1, input X1 is connected to J thermocouple (measuring range 0 to 4).
00°C), and a thermocouple (measurement range 0 to 400°C) to input X2.
℃) will be explained as an example.

Amplifier 71ij that amplifies input X1: When the level range of input X1 (O~21.846mV) is input, A/
The degree of amplification is adjusted so that the conversion result by the D conversion circuit 5 is in the range of 0 to 2000.

Furthermore, when the level range (0 to 16.395.nV) of the human power X2 is input, the amplifier 72 that amplifies the human power
The amplification degree is adjusted so that the converted value by the /D conversion circuit 5 is the same (in the range of 0 to 2000).

The local CPU 4 selects one of the human power inputs X11X2 by the multiplexer 6, performs A/D conversion by the A/D conversion circuit 5, and transfers the resulting A/D conversion 1 straight to the switch by the bus controller 2. "By turning on f, the data is written to the common memory 6.

On the other hand, the host cPU 1 uses the bypass controller draw 22 to turn off the switch 2 and turn on the switch 1 for the A/D conversion value of each human power X 1 * X 2 written in the common memory 6. and read it.

The CPU performs linearization processing on the read data to linearize the non-linear characteristics of the heat 1 pair using a broken line approximation using a knot, converts it into temperature, and obtains a measurement result.

FIG. 2 is a graph for explaining the principle of the linearization processing operation. In the figure, the horizontal axis represents the temperature of the thermocouple input terminal, and the vertical axis represents the A/D conversion value (read data) of the thermocouple output voltage, which is the characteristic curve (a), and the straight line (b). indicates the broken line of the broken line approximation.

If the data read by the host CPU 1 from the common memory 3 is DT, the known read data Dm.

Known linearization data NmyNm for Dm-1
-1, and perform the calculation according to the following formula to obtain the read data DT.
Obtain linearization data NT for .

In addition, the above formula (1) holds true because: a mouth DT-Dm b”　Dm-1-Dm d””Nm-t-N(H c=Ny-Nm If you put C-2 x d b This is because it holds true.

FIGS. 3(a) and 3(b) are explanatory diagrams showing the storage status of linearized data, and FIG. 6(c) is an explanatory diagram showing a table of data start addresses of the data numbers.

That is, in FIG. 3(a), as data 1, J
The reading data of its output for the thermocouple (DOLDl...
...Dm) and its linearized data (N o +
N1...Nm) are stored as a table in a corresponding manner. Figure 6 (
b) is for the K thermocouple and is shown exactly as data 2.

FIG. 3(C) shows that the start address of data 1, the start address of data 2, etc. are tabulated.

FIG. 4 is a flowchart showing the operation flow when the CPU executes the linearization processing operation described above with reference to FIG. 2.

The processing operation flow of the CPU will be explained with reference to FIGS. 3 and 4. First, in step ■ in Figure 4, the CPU:
Since a data number corresponding to the thermocouple used is given, the address table shown in FIG. 3(C) is referred to using the data number to find the leading address. If the thermocouple used is a J thermocouple, the corresponding data number is 1, and as shown in FIG. 3(a), the read data D
Since the linearization data Nm and the linearization data Nm are stored in a corresponding manner, the CPU can read them from now on.

Next, in step (2), the read data DT at that time
is input.

Then, the process moves to step (2), and it is checked whether the input data DT is between what stored data Dm and the adjacent stored data Dm-1. That is, some stored data D
Select m and compare it with DT, and if DT≧Dm does not hold, in step (2), set m to (m+1) and return to step (2), and repeat the same process.

Then, when DT≧Dm holds true, DT becomes Dm and I)m−
It turns out that it is between +, so the CPU steps ■
, and the required data Dm, NmlDm-1°Nm-
1 from the storage memory and performs the same calculation as in equation (1) above to obtain the linearized data NT for the input data DT.

Now, as explained above, in the conventional A/D conversion method, when the type of thermocouple connected to the multiplexer via the amplifier and the measurement target (different temperature range), that is, the input type, differ accordingly. It was necessary to use an A/D conversion circuit. In other words, if the input type changes and the input level change range changes significantly, the same A
/D conversion circuit cannot convert (this makes it necessary to use another conversion circuit or adjust the amplification degree of the amplifier).

In other words, if the type of thermocouple used as a measuring device or the object to be measured differs depending on the customer's specifications, the A/D may differ accordingly.
There were many cases in which a conversion circuit had to be used, which resulted in a failure in mass production and increased costs.

[Problem that the invention seeks to solve]

Therefore, the present invention aims to solve the problem of making it possible to use the same A/D conversion circuit even if the type of thermocouple used as a measuring device or the object to be measured differs. Therefore, it is an object of the present invention to provide an A/D conversion method that makes the above possible.

[Means for solving problems]

In the A/D conversion method according to the present invention, the degree of amplification is determined so as to take a certain output level range according to the human power level range of the input signal, which is made up of measurement signals obtained by measuring the measured quantity with various measuring instruments. a plurality of amplifying means, and an analog-to-digital (A/D) conversion for manually converting one of the outputs of the plurality of amplifying means selected through a multiplexer into a digital signal of a predetermined number of bits. and a CPU (Central Processing Unit) to which the A/D converted digital quantity of the predetermined number of bits is input as data.

[Effect]

The CPU selects a certain constant value (natural number) S selected within the maximum number of quantization levels determined by the number of output bits of the A/D converter, and sets 0 to S to 0 to 100%. When the value of S at the specified time (standard 100% value) is given, and the measurement signal obtained by measuring a certain measured quantity VS is A/D converted by the A/D converter. The measured quantity 11VS whose digital value becomes the reference 100% value S is given to the measuring instrument as a reference value of the measured quantity, and the measured quantity in the measuring instrument and the quantity obtained by linearizing it. Each measuring device has a linearization processing data table in which a data string showing the relationship between
When the converter output (digital data) and a signal indicating the measuring device that generated the data are input, the reference 100% value S and the measured quantity reference value VS are used from the data. The present invention is characterized in that the quantity to be measured is calculated by calculation, the linearization process for the quantity to be measured is performed by calculation by referring to the IJ nearization processing data table, and the result is output.

〔Example〕

Next, one embodiment of the present invention will be described with reference to the drawings.

As mentioned earlier, the hardware configuration of the present invention is /\ This is as shown in Figure 1.

In FIG. 1, if the number of output bits of the A/D conversion circuit 5 is 12 bits, the maximum number of quantization levels is 4o.
96 (-2"). Therefore, as long as the input signal level (thermocouple output voltage) does not exceed this range,
Any type or measurement range of thermocouples can be used.

Of the maximum number of quantization levels 4096 (approximately 4000 below), 0 to 20
The range of 00 is considered to be 0 to 100%, and the number of quantization levels 2000 corresponding to 100% will be called the reference 100% value S.

On the other hand, in each measuring device (thermocouple), at what temperature is measured, the output of the A/D converter (quantization level number) is 200.
The value of whether the temperature becomes 0 (100%) is determined, and this temperature is now set as the reference temperature Ts.

The host CPU 1 determines the reference temperature Ts for each measuring device and A
/ Reference 100% value S of the D conversion circuit 5 (in this case, 2
000), the local CP
When data about the output X of the A/D conversion circuit 5 and the corresponding measuring device are given from U4 via the common memory 3, the measured temperature Y at that time can be calculated backwards using the following formula. can.

However, VS is the measuring device output voltage (
It is assumed that the CPU 1 can easily obtain VS if the reference temperature Ts is given.

Next, the CPU 1 refers to a table for linearization processing provided for each measuring device, performs linearization processing on the calculated temperature Y, and outputs the result.

Figure 5 (a), (b), and (c) show examples of data used for linearization for J thermocouple (data number 1), K thermocouple (data number 2), and R thermocouple (data number 3). Show things. For each theta, nT is the temperature, nV is the temperature n
The thermoelectromotive voltage corresponding to T is expressed in μ■.

FIG. 5(d) is an explanatory diagram showing a table of data start addresses for each data number.

Note that since FIG. 5 is an explanatory diagram similar to FIG. 3 described above, no further detailed explanation is necessary.

FIG. 6 is a flowchart showing the flow of processing operations of the above-mentioned host CPU 1.

The operation of the host CPU 1 will be described below with reference to FIGS. 5 and 6. First, it is assumed that the CPU 1 receives data X measured by the J thermocouple. Then,
The host CPU 1 refers to the address table in FIG. 5(d), learns the address of data 1 from the data number (1) for thermocouple J, and refers to data 1 in FIG. 5(a). become able to.

Therefore, in the su-tsub ((a) of Figure 6, give △ in advance. Once it is found, proceed to step ?e, and the found t
The thermoelectromotive voltage data vS corresponding to T is read from data 1.

Next, proceeding to step @, the measurement data X is converted into temperature Y using the above-mentioned equation (2).

After that, through step 6 (D), the linearization processing result Z of the temperature Y is obtained.

Note that steps ①, 6, and (D) are exactly the same as steps ①, ②, and ② in FIG. 4 described earlier, so their explanations will not be repeated.

In the above explanation, it has been explained that the host CPU 1 converts the measurement data into temperature and performs the linearization process, but the present invention is not limited to this. , host) The load on the CPU may be reduced.

Further, in thermocouples, reference junction compensation is generally performed, and as an example of this, the node configuration is shown in FIG. 7, and the flow of processing operations of the CPU is shown in FIG. 8.

The configuration shown in FIG. 7 differs from the configuration shown in FIG. 1 in that only one resistance temperature detector 8 (platinum Pi) is provided to measure and input the terminal temperature TA of the thermocouple.

In addition, in FIG. 8, in steps S1 to S6, the electromotive force VTA of the thermocouple corresponding to the terminal temperature TA is
The difference from the flowchart in Fig. 6 is that the reference junction is compensated by calculating it from the linearization data table shown in the figure and then adding it to the measured temperature (voltage) Y in step S4.The other points are the same. be.

〔Effect of the invention〕

As explained above, according to the present invention, one type of A/
The D conversion unit can A/D convert and linearize various inputs, so for example, if a thermocouple is input and an A/D conversion circuit with 8 points per unit is configured, the thermocouple will be 5 points. Since there are different types, it is possible to achieve the effect that 58 (=390,625) types would be required to correspond to all inputs, but one type can be used.

[Brief explanation of drawings]

FIG. 1 shows the hardware configuration of an embodiment of the present invention, and
A block diagram that can also be used to explain the conventional technology, FIG. 2 is a graph for explaining the principle of the linearization processing operation executed by the CPU in FIG. 1, and FIGS. 3 (a) and (b) Id
! j Figure 3 (C) is an explanatory diagram showing the storage status of the linearized data, Figure 3 (C) is an explanatory diagram showing the table of data start addresses of the data number, Figure 4 is a flowchart of the linearization processing operation, Figure 5 (a) . (b) and (C) are explanatory diagrams showing the storage status of linearized data in one embodiment of the present invention, and FIG.
) is an explanatory diagram showing a table of data start addresses of the data number, FIG. 6 is a flowchart showing the flow of processing operations in one embodiment of the present invention, and FIG. 7 is a hardware configuration of another embodiment of the present invention. FIG. 8 is a flowchart showing the flow of processing operations of the CPU in FIG. 7. Explanation of symbols 1...Hos) CPU, 2...Path controller, 3...Common memory, 4...
・Local CPU, 5...A/D conversion circuit, 6
...Multiplexer, 71~7n...
Amplifier, 8...Resistance temperature sensor, agent, patent attorney
Akio Namiki Agent Patent Attorney Kiyoshi Matsuzaki Input □ Figure 3 Axis) (b) (c) Figure 4 Figure 5 (a) (b) (c)
(d) Figure 6 Figure 7

Claims (1)

[Claims] 1) The amplification degree is determined so that each of the various measuring instruments takes a fixed output level range according to the input level range of the input signal consisting of the measurement signal obtained by measuring the measured quantity. a plurality of amplification means, and an analog/digital (A
/D) A converter, and a CPU (Central Processing Unit) that receives the A/D converted digital amount of the predetermined number of bits as data, and the CPU receives the output bits of the A/D converter. When a certain numerical value (natural number) S selected within the range of the maximum quantization level number determined by the number is selected and 0 to S is set as 0 to 100%, the value of this S (reference 100% value ), and the digital value obtained when the measurement signal obtained by measuring a certain measured quantity V_S by the measuring instrument is A/D converted by the A/D converter becomes the reference 100% value S. Using the measured quantity V_S as the measured quantity reference value, each measuring instrument receives a data string that is given to each measuring instrument and indicates the relationship between the measured quantity in the measuring instrument and the quantity obtained by linearizing it. It has a separate linearization processing data table, and the A/D converter output (
When a signal indicating the measuring device that generated the data (digital data) and the measuring device that generated the data is input, the measured value is calculated from the data using the reference 100% value S and the measured quantity reference value V_S. An analog-to-digital conversion method characterized in that the amount is calculated, the linearization processing of the measured quantity is performed by calculation with reference to the linearization processing data table, and the result is output. 2) In the analog-to-digital conversion method according to claim 1, the CPU includes a host CPU and a local CPU, and the local CPU controls the conversion operation by the A/D converter and converts the converted digital data. The host CPU receives the reference 100% value S, the measured quantity reference value V_S, and the linearization processing data table, calculates the measured quantity, and linearizes the measured quantity. An analog-to-digital conversion method characterized by processing. 3) The analog-to-digital conversion method according to claim 1, wherein the CPU also performs reference junction compensation processing on input digital data.