JPS5814604B2 - Linearity compensator in conveyor scale - Google Patents

Description

[Detailed Description of the Invention] The output characteristics of the load cell (load cell) attached to the conveyor scale that converts the load into voltage are not perfectly linear in proportion to the load and distortion occurs. When converted to digital data, as shown in Figure 2, when the zero point and each point at 100% load factor are aligned with the ideal straight line a, the output will have distortion characteristics in the lower direction,
It is not possible to obtain an actual digital output proportional to the load factor, and an error due to distortion occurs.In the case of an integration type such as a conveyor scale, the error is also integrated as a result, and the error increases in proportion to the integration time. It turns out.

Therefore, in order to prevent the occurrence of the above-mentioned errors as much as possible, the present invention provides an apparatus that improves the accuracy of a conveyor scale by correcting the integrated value proportional to the load to compensate for linearity.

The details are shown in the accompanying drawings and will be explained in conjunction with examples.

1 is a load converter such as a load cell, and this load converter 1 detects the instantaneous weight of an article conveyed by a conveyor,
It generates an analog signal Vw proportional to the weight.

2 is an analog/digital converter, which is the load converter 1 mentioned above.
This converts the analog signal Vw from the digital signal a into a digital signal a.

3 is a pulse transmitter that generates a signal P with a number of pulses per unit time that is proportional to the conveyance speed of the conveyor;
This generated pulse is configured to be clocked into the rate multiplier 4 at the next stage.

Further, the output digital signal a from the analog-to-digital converter 2 is inputted as an address signal to the next read-only memory 6, and simultaneously inputted to the adder 7 as an addend input signal.

As an input to the read-only memory 6, the upper required digits (for example, the first two digits) of the digital signal a serve as an address signal, and the correction value △a written in advance by specifying the address is The digital signal a is read out and input as an addend to the adder 7, where the digital signal a and the correction value Δa are added together, ie, a+Δa.

The above signal a+Δa is given as a rate input to the rate multiplier 4, and its multiply output Po is the integrated value of the integrator 5.

The present invention has the above-mentioned configuration, and in terms of its operation, the load of the article conveyed by the conveyor is measured by the load converter 1, and an analog signal Vw of the instantaneous weight proportional to the load is generated. The signal is input to an analog-to-digital converter 2 and converted into a digital signal a.

Therefore, the upper two digits of the digital signal a are input to the read-only memory 6 as an address designation signal, and the pre-written correction value Δa is read out, and the next adder 7 reads out the correction value Δa. Digital signal a and correction value △a
, that is, (a+Δa) is performed, resulting in a value approximately equal to the value of the ideal curve a, which is given as the rate input to the rate multiplier 4.

Therefore, the signal P transmitted from the pulse transmitter 3 per unit time proportional to the conveyance speed of the conveyor is multiplied as a clock input, and its output Po is integrated in the next totalizer 5, and The total weight will be determined.

As described above, the present invention provides an analog-to-digital converter 2
A read-only memory 6 which uses digital signal a as an address signal is provided between the output side of the rate multiplier 4 and the rate input side of the rate multiplier 4, and a correction value Δa of a certain value is output by address specification. , the correction value △a is added to the digital signal a to make it a value corresponding to the ideal curve a, which is used as the rate input of the rate multiplier 4, so that the error with respect to the distortion characteristics of the load converter 1 is reduced. This is compensated by the correction value Δa of the read-only memory 6, which has the effect of enabling highly accurate measurement.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the present invention, and FIG. 2 is a characteristic curve diagram showing the relationship between the output of an analog-to-digital converter and the load factor. 1...Load converter, 2...Analog/digital converter, 3...Pulse oscillator, 4...
... Multiplier to relay 1, 5... Totalizer, 6... Read-only memory, 7...
...Adder.

Claims (1)

[Claims] 1. A load converter that generates an analog signal proportional to the instantaneous weight of the article conveyed by the conveyor, an analog-digital converter that converts the analog signal into a digital signal, and a unit time proportional to the conveyance speed of the conveyor. a pulse oscillator that generates a signal with a number of pulses corresponding to the number of pulses hit, a rate input of the digital signal from the analog-to-digital converter, and a clock input of the pulse signal from the pulse oscillator. In the conveyor scale that integrates the output, a read-only memory is connected between the output side of the analog-to-digital converter and the rate input side of the rate multiplier, using the upper required digits of the output of the analog-to-digital converter as an address signal. , a linearity compensation device for a conveyor scale, comprising an arithmetic circuit that adds the output signal of the read-only memory to the output of the analog-to-digital converter.