JPS62129725A - Load-cell type balance - Google Patents

Abstract

PURPOSE:To improve dependability of function checking, by switching an analogue switch to the reference voltage source side and performing an operation check of an A/D convertor. CONSTITUTION:A micro-processor PU5 switches an analogue switch 2 into the other contact point 22 to operate an A/D convertor 3. By this arrangement, the reference voltage from the reference voltage source 4 is read into the PU5 through the convertor 3. On the PU5 an input signal and a set range are compared and if the signal is within a set range, the function of the convertor 3 is identified as normal and if not, the function of the convertor 3 is identified as abnormal and an error is indicated on a display 6. Thus, checking of the convertor 3 is available independently of a load-cell 1 for it functioning. Further, by switching of the switch 2, an abnormality of the cell 1 can be identified.

Description

[Detailed description of the invention] “Industrial application field” The present invention relates to a load cell scale.

[Prior Art] A load cell scale is equipped with a load cell that outputs a voltage signal according to the load, and the voltage from the load cell (K is A/
The data is converted into a digital signal by a D converter and taken into a microprocessor, and the microprocessor converts it into weight data in Durham units, for example, and displays it on a display.

Conventionally, when performing a circuit check using such a load cell type scale, a weight was placed on the load cell, and at that time the display displayed! I was reading and checking If m.

[Problems to be Solved by the Invention] However, with this conventional checking method, even if an abnormality appears in the displayed weight, it is difficult to determine whether it is due to an abnormality in the load cell or the A/D converter. There were some issues where I couldn't do a thorough check.

This invention was devised to solve this problem, and it is possible to check the A/D converter independently. Therefore, if an abnormality occurs in the weight display, it can be determined whether it is due to a failure of the load cell or not. It is an object of the present invention to provide a load cell type f·i' that can reliably determine whether the problem is due to a failure of the A/D converter and can improve the reliability of the check.

[Means for Solving the Problems] This invention converts a voltage signal from a load cell that outputs a voltage signal according to the load into a digital signal using an A/D converter, and displays weight based on the digital signal. In a load cell type scale, a reference voltage source is provided and the voltage signal from the load cell is input to the input section of the A/D converter. An analog switch is provided to switch input to the device, and by switching the analog switch to the load cell side, a measuring operation is performed, and by switching the analog switch to the reference voltage source side, the operation of the A/D converter is checked.

[Function] In the present invention having the 11'4 configuration, when checking the operation of the A/D converter, the analog switch is used! ! ■Switch to the voltage source side, input the reference voltage from the reference voltage source to the A/D converter, convert it to a digital signal, and read the digital value to determine whether the A/D converter is operating normally or abnormally. When carrying out normal weighing operations, the analog switch is switched to the load cell side, and a voltage signal corresponding to the load from the load cell is input to the A/D converter.

[Example code] An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, a load cell 1 that generates a voltage signal depending on the load is provided, and the voltage signal from the load cell 1 is input to the A/D converter 3 via one contact 2 of an analog switch 2. are doing. It also generates a reference voltage corresponding to a predetermined weight 2! A quasi-voltage source 4 is provided, and a reference voltage from the reference voltage source 4 is input to the A/D converter 3 via the other contact 22 of the analog switch 2.

First, the contacts of the analog switch 2 are controlled by the microprocessor 5.

The A/D converter 3 is started to operate by the microprocessor 5, converts an input voltage signal into a digital signal, and outputs the digital signal to the microprocessor 5.

When the analog switch 2 is switched to the load cell side, that is, to one of the contacts 21, the microprocessor 5 performs normal weighing operation control and converts the digital signal from the A/D converter 3 into weight data in duram units, for example. and display it on the display 6.

Further, when the microprocessor 5 checks the operation of the A/D converter 3, it performs the control shown in FIG.

This control first drives the analog switch 2 and switches its contact to the standard voltage source side, that is, the other contact 22.

Then, a control signal C is output to the A/D converter 3 to start the A/D conversion operation of the A/D converter 3, and a digital signal from the A/D converter 3 is taken in. Next, this digital value is compared with data that determines a preset normal range, and if it is within that range, A/D conversion 2 is performed.
; It is determined that the operation in step 3 is being performed normally, and the analog switch 2 is switched to one contact 21 to enable normal weighing operation. Further, when the digital value is outside the normal range, it is determined that the operation of the A/D converter 3 is abnormal, and an error message is displayed on the display 6.

In this embodiment with such a configuration, A/D”A
When checking the operation of the switch 3, switch the microprocessor 5 or the analog switch 2 to the other contact 22,
The A/D converter 3 is operated. As a result, the reference voltage source 4
The fundamental voltage from the microprocessor 5 is A/D converted by the A/D converter 3 and taken into the microprocessor 5. Then, the digital signal input to the microprocessor 5-C is compared with the setting range, and if the digital value is within the setting range, the A/D converter 3
If the operation of the A/D converter 3 is determined to be normal, and if the digital value is outside the setting range, the operation of the A/D converter 3 is abnormal.
If there is, it will be judged 1tli. If it is determined that there is an abnormality, an error message is displayed on the display 6 to inform you of the error.

In this way, since the A/D converter 3 is separated from the load cell 1 and its operation can be checked independently, the operating state of the A/D converter 3 can be checked reliably. And A/D
When the converter 3 is determined to be normal and the analog switch 2 switches to one of the contacts 21, a weight is placed on the load cell 1, and if the display 6 does not display the original weight value, the load cell 1 is abnormal. It is possible to judge that. In this way, since the operation check of the A/D converter 3 and the operation check of the load cell 1 can be performed separately, highly reliable checks can be performed.

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

Note that the same parts as those in the above embodiment are designated by the same reference numeral 71, and detailed explanation thereof will be omitted.

As shown in FIG. 3, this uses a D/A converter 41 as a reference voltage source, and this D/A converter 41 is controlled by a microprocessor 5. That is,
The microprocessor sensor 5 supplies a desired digital signal to the D/A converter 41 and controls the D/A converter 41 to generate a desired capacitance voltage.

When the microprocessor 5 checks the operation of the A/D converter 3, it performs the control shown in FIG.

First, the analog switch 2 is driven and its contact is switched to the D/A converter 41 side, which is the reference voltage source, ie, the other contact 22.

In this state, a desired digital signal is supplied to the D/A converter 41 to set the level of the base voltage output from the D/A converter 41 to a desired level. outputs the control signal C to the A/D converter 3, and outputs the control signal C to the A/D converter 3.
The conversion operation is started and the digital signal from the A/D converter 3 is taken in.

Next, this digital value is compared with data that determines a preset normal range, and if it is within that range, it is determined that the A/D converter 3 is operating normally.
The same process is performed again by changing the value of the digital signal supplied to the A converter 41.

Of course, the normal range to be compared this time is different from the previous one. In this way, while changing the digital value supplied to the D/A converter 41, the operation of the A/D converter 3 is checked by comparing the digital value from the A/D converter 3 with each set normal range. do. If all checks are judged to be normal, the analog switch 2 is switched to one contact 21.
switch to enable normal weighing operation. In addition, in each of these checks, if it is determined that even one digital value from the A/D converter 3 is out of the normal range, it is determined that the operation of the A/D converter 3 is abnormal, and the display 6
An error message will be displayed.

With such a configuration, if the level of the reference voltage output from the D/A converter 41 is varied in a plurality of ranges corresponding to the weighing range of the load cell 1, A/D conversion at each point can be performed. The operation of the converter 3 can be checked, and the linearity of the A/D conversion of the A/D converter 3 can also be checked, making it possible to perform a more reliable check.

In the above embodiment, a D/A converter was used as the base voltage source and it was controlled by a microprocessor, but the invention is not limited to this, and a variable resistor may be used and switched by external operation. The reference voltage may be varied.

[Effects of the Invention] As detailed above, according to the present invention, it is possible to check the A/D converter independently, and therefore, when an abnormality occurs in the iIf Q display, it is possible to check whether it is due to an abnormality or a failure of the load cell. Load cell type f that can reliably determine whether the problem is due to an A/D converter failure and improve the reliability of the check.
・It is something that can provide “.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 is a flowchart showing A/D converter operation change processing by a microprocessor in the same embodiment, and FIG. 3 is a block diagram showing another embodiment of the invention. The block diagram shown in FIG. 4 is a flowchart showing A/D converter operation check processing by the microprocessor in the same embodiment. 1...Load cell, 2...Analog switch, 3...
・A/D conversion:) Poetry, 4. Basic voltage source, 5. Microprocessor. Applicant's agent Patent attorney Takehiko Suzue 4 Cause 1 Figure 2

Claims (2)

[Claims] (1) A reference voltage source is provided in a load cell type scale that converts a voltage signal from a load cell that outputs a voltage signal according to the load into a digital signal using an A/D converter, and displays weight based on the digital signal. At the same time, the voltage signal from the load cell is input to the input section of the A/D converter.
The voltage signal input to the converter or from the reference voltage source A
An analog switch is provided to switch the input to the A/D converter, and by switching the analog switch to the load cell side, a weighing operation is performed, and by switching the analog switch to the reference voltage source side, the operation of the A/D converter is checked. Features a load cell scale. (2) The load cell type weigher according to claim 1, wherein the reference voltage source is capable of externally varying the level of the output voltage signal.