JPS617918A - Multipoint analog input device - Google Patents

Abstract

PURPOSE:To curtail a zero or span adjustment by storing data of a zero point and a span point of each analog signal in a memory, and deriving a theoretical value of the analog signal inputted thereafter, from a theoretical value corresponding to said data. CONSTITUTION:First of all, input signals Vi1-Vin are also set to 0%, a switch S1 is closed and a command for inputting an input quantity to a CPU5 is generated. As a result, a value of 0% of each analog quantity is inputted through a multiplexer 2 and stored in a memory 6. Subsequently, the input signals Vi1- Vin are set to 100%, switches S2, S3 are closed, and when a command is generated in the CPU5, a value of 100% of the input signal is stored in the memory 6. The unknown quantity inputted thereafter can be calculated easily from a theoretical value of that time and a digital value of the time of 0% and 100%. In this way, when deriving the theoretical value, the difference between a zero point and a scan point is calculated, therefore, a drift offset quantity existing on the way is offset, and accordingly, the operation can be executed exactly.

Description

[Detailed Description of the Invention] [Technical Field to Which the Invention Pertains] This invention is a method of importing analog quantities represented by various process lids such as temperature and pressure into a digital processing device such as a microcomputer (simply referred to as a microcomputer). The present invention relates to a multi-point analog input device for use in a computer.

[Prior art and its problems]

FIG. 4 is a block diagram showing a conventional example of such an analog input device. In the figure, 1 (11-1n).

3 is an operational amplifier, 2 is a multiplexer,
4 is an analog/digital (A/D) converter, and 5 is a digital processing unit (CPU) such as a microcomputer. Note that R11, R12 to Rnl s Rn2 are resistors, and R1
4p Rts -Rn4 j FLn5 is a variable resistor.

In such a configuration, each analog quantity from the operational amplifiers 11 to 1n is sequentially selected by the multiplexer 2,
After being appropriately amplified by the operational amplifier 3, the A/D converter 4
is converted into a digital quantity and taken into the CPU 5. The operational amplifier 1 used here has different characteristics depending on its constituent elements, such as resistors. However, since this adjustment is performed for each input unit, as the number of input points increases, not only does the time required for W4 adjustment become wasted, but the number of parts increases, making it expensive. It has its drawbacks.

[Purpose of the invention]

The present invention has been made in view of the above, and an object of the present invention is to provide an analog input device that can reduce the number of parts and time for zero or span adjustment.

[Key points of the invention]

This invention focuses on the fact that a memory is generally used in a digital processing device, and stores the data of the zero point and span point of each analog signal in advance in this memory, and stores this data and the corresponding data. By determining the theoretical Wk value of the analog signal input thereafter from the theoretical value, adjustment for each input point is not required.

[Embodiment of the Invention] FIG. 1 is a block diagram showing an embodiment of the invention, and FIG. 2 is a graph for explaining the conversion operation of an unknown analog input amount into a theoretical value.

#! As is clear from FIG. 1, this embodiment has switches 81 to S3 and 6% random access memory (RAM) compared to the one shown in FIG. Then, the input signal V is as follows:
The feature is that the values of 0% and 100% of i1 to Min are taken in, respectively.

That is, first, all input signals 11 to Min are set to 0%.
At the same time, it closes the switch S1 and issues a command to the CPU 5 to take in the 0% value of the input amount. Note that at this time, switch S3 is also closed.

As a result, the 0% value of each analog quantity is converted into a digital quantity and taken in via the multiplexer 2, and the memory 6 sequentially stores these digital quantities. Next, input signals Vil-Vi.

After setting all values to 100%, the switch Sm is opened and the switch S2sS3 is closed. A command is issued to the CPU 5 to take in the 100% value of the input signal, so the input signal is input in the same manner as above. 100% values (digital quantities) of the signals are sequentially stored in the memory 6. Note that after that, by opening the switch S3, rewriting to the memory 6 is prevented and data is prevented from disappearing.

0% at any point, 10 obtained in this way
Let the digital amount at 0% be POlPloo,
In addition, the corresponding theoretical values are DO and Dloo, respectively.
Furthermore, the unknown quantity that will be input later at this point is P
Assuming that x, it can be seen that the theoretical value Dx at that time can be obtained as follows. This is clear from the graph in Figure 2, but the measured value (Po z Ploo ) obtained like the straight line B is converted to the theoretical value (D
o, Dloo), and can be obtained using a simple proportional relationship. At this time, if the characteristics of the operational amplifier at each human power point are different, the measured values POp P 100 will also be different from each other, so even if the unknown quantity Px is the same, the obtained theoretical value Dx will be different from each other. Needless to say, it is different for each input point.Also, as is clear from the above equation, since the difference between the zero point and the span point is calculated when calculating the theoretical IDx, there are Since the amount of drift or offset is canceled out, accurate calculation is possible.

FIG. 3 is a block diagram showing another embodiment of the present invention.

As is clear from the same figure, the operational amplifiers 11 to 1n and resistors RotR12s as shown in FIG.
The feature is that R13 to Rn1 p ELn2 J Rn3 are removed to achieve a significant cost reduction, and the rest is the same as in FIG. 1.

In any of the above embodiments, by appropriately updating the zero and span data stored in the memory,
It is also possible to eliminate the influence of drift due to aging and the like.

〔Effect of the invention〕

According to the invention, zero of each input analog quantity.

Data at span points is measured and memorized, and this measured data and the corresponding theoretical value are used to determine the theoretical value of the unknown analog quantity, which eliminates the need for manual or mechanical adjustment parts and the associated work. This has the advantage of not only being omitted but also reducing costs.

Furthermore, since the unknown analog quantity is converted into a theoretical value by calculation, it is possible to remove the drift or offset of the intervening circuit. Furthermore, by appropriately updating the zero and span data stored in the memory, it is possible to eliminate the influence of drift due to aging and the like.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a graph for explaining the conversion operation according to the present invention, FIG. 3 is a block diagram showing another embodiment of the present invention, and FIG. FIG. 2 is a configuration diagram showing a conventional example. Code explanation 1 (11~'n), 3... operational amplifier, 2... multiplexer, 4...
・Analog/digital (A/D) converter, 5...
...Digital processing device (microcomputer),
6...Random access memory, T I '=
Tn...Input signal terminal, R11p R12t
R13 ~ RHI x Rn2 y Rn3 """ Resistor, R14p R15 ~ Rn4 J Rn5 "Variable resistance, 81-83...Switch. Agent Patent Attorney Akio Namiki Agent Patent Attorney Kiyota Matsuzaki Figure 1 Figure 3

Claims (1)

[Claims] In a multi-point analog input device for sequentially selecting analog signals from multiple locations, converting each into digital values, and inputting them into a digital processing device, the zero point and span point of each analog signal read in advance by the processing device are It is characterized by comprising a storage means for storing each digital value, and an arithmetic means for calculating a theoretical value of an unknown analog signal to be inputted thereafter from the stored value and the corresponding theoretical value. Multipoint analog input device.