JPS6045807B2 - Span adjustment device for belt scale - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a belt scale configured to continuously integrate instantaneous weight over a working length and display the total transportation amount.

The belt scale has a load detection roller pressed against an endless strip (hereinafter referred to as a belt) that conveys the object to be weighed, detects the weight via the belt, and measures the amount of movement of the load detection roller using a strain gauge. converting it into an analog voltage value using a load converter such as a formula load cell, further converting the movement amount into a digital signal via an analog-to-digital converter, and then multiplying it by the conveyance speed signal of the belt, The system is configured to calculate instantaneous transport volume.

However, such a belt scale may cause measurement errors due to the following reasons. In other words, changes in the input/output characteristics of the load converter itself, changes in the input/output characteristics of the analog/digital converter, and changes in the amplification circuit of the DC amplifier interposed between the load converter and the analog/digital converter. The cause of the measurement error is a change in the amplification degree due to a change in the resistance value. Figure 4 shows changes in the input/output characteristics of the load converter, and shows changes in the input/output characteristics of the load converter. and the voltage V. is the normal characteristic I when it is output, and when this changes to the higher gain side, the load G is output as in the characteristic ■. Load G in normal characteristic I even though a load G1 smaller than is applied. The same voltage V as when loaded. is output, and in the device downstream from the load converter, the actual load is G.
, even though G. is processed as (Go - G,), resulting in a measurement error of the difference. Similarly, when the gain fluctuates to the lower side, the load G is larger than the load Go, as shown in characteristic (■). is loaded, the voltage Vo is output, and in this case, in the device downstream from the load converter, (G
. -Go) measurement error occurs. i 4th as above
A change in the normal characteristic I shown in the figure as shown in ■ or ■ is generally called a "span change," and the operation of returning the characteristic ■ or ■ to I is called a "span adjustment J."

This also applies to the input/output characteristics of analog-to-digital converters and the input/output characteristics of belt scales. Therefore,
If the span of the integrating device changes in the belt scale that integrates the instantaneous transport amount, unless the span is adjusted, the wrong transport amount will be integrated, making it impossible to obtain an accurate total transport amount.

Therefore, the present invention provides a span adjustment device that can eliminate the influence of the error component on the total transportation amount by an extremely simple operation.

The span adjustment device for the belt scale of the present invention is based on the output of the load conversion device that detects the instantaneous weight on the working length when the belt scale is in no-load operation and in a balanced state where a certain instantaneous weight is simulatively loaded. The weight obtained by subtracting the constant instantaneous weight is accumulated during n rotations of the belt, and the average value of the weighing error due to the change in span is calculated from the accumulated value, the rotation speed n, and the number of working lengths for the entire circumference of the belt. However, the output of the load converter during transport operation can be corrected based on the average value of this measurement error.

An embodiment of the present invention will be described below with reference to the drawings.

1 is a belt conveyor consisting of a belt 2; 3 is a load conversion unit that measures weight via the belt 2; and 3 is a load conversion unit that measures the weight via the belt 2, and is arranged in the conveying direction so as to support the outbound belt 2 on which the raw material is placed from below. A measuring roller 3a presses against the belt 2 from below at an intermediate position between carrier rollers 2a and 2b arranged at a predetermined interval along the vertical movement of the measuring roller 3a. It is composed of a load cell 3b that converts the signal A into an analog signal A, and a lever 3C that transmits the vertical movement of the measuring roller 3a to the load cell 3b.

4 is a pulse transmitter, the rotating shaft of which is connected to an idling roller 4a that comes into contact with the belt 2 on the return path, and is proportional to the belt running speed!
A pulse train signal P having the same frequency is output.

5 is an analog-to-digital converter generally known as a ratio multiplication type A/D converter, and the output of the load cell 3 is inputted to the unknown voltage input terminal Vx based on the voltage inputted to the reference voltage input terminal ■r. Signal A as digital value D
Convert to 1.

The analog-to-digital converter 5 and the load converter 3 function as a load converter 6. 7 is a transportation amount accumulation unit which calculates the instantaneous transportation amount from the instantaneous weight Dg output from the analog-to-digital converter 5 and the pulse train signal P from the pulse transmitter 4, and accumulates the sequentially calculated instantaneous transportation amounts to calculate the total transportation amount. Outputs a signal according to the amount.

Reference numeral 8 denotes a total transportation amount display device, which digitally displays the output of the transportation amount accumulation section 7 as a weight value.

Reference numeral 9 denotes a balancing device, which is configured to load a weight 9a onto the rod of the lever 3C of the load converter 3 on the measuring roller 3a side;
At least when the belt 2 is in no-load operation, the weight 9
A weight support device (not shown) that pushes up the weight 9a acts to prevent the weight 9a from acting on the lever 3C.

Note that the lever 3C connects the load cell 3b, which exhibits only a slight displacement, and the measuring roller 3a, so even when the weight 9a acts on the lever 3C during no-load operation. , the measuring roller 3a is in pressure contact with the belt 2, and is in a state where non-uniformity of the belt 2 can be detected. Reference numeral 10 denotes a first setting device, which is set to n-M if the number of pulses generated by the pulse generator 4 during one revolution of the belt 2 is M.

11 is a second setting device, and the balancing device 9 is connected to the load cell 3.
An instantaneous weight value GO to be applied to b in a simulated manner is set.

FIG. 3 shows a processing device 12 that calculates the average value of weighing errors due to span changes.

13 is a subtracter which converts the instantaneous weight value G from the instantaneous weight signal Dg output from the analog-to-digital converter 5;

The error amount Δg obtained by subtracting Δg is output. 14 is a counter,
Count the number of pulse signals output by pulse generator 4.

A coincidence detector 15 detects that the contents of the counter 14 match the contents of the first setter 10.

16 is an integrator that sequentially accumulates the error amount Δg of the output of the subtracter 13 until the coincidence detector 15 detects a coincidence;
The cumulative value A is output.

Reference numeral 17 denotes an arithmetic device which outputs the working length number B of the working length L of the load converter 3 relative to the entire circumference of the belt 2, the output signal of the first setter 10 as a signal corresponding to the rotational speed n of the belt 2, and the The cumulative value A is accepted, and the average value C of the weighing error due to the span change is calculated by the process of.

Reference numeral 18 denotes a reference voltage generation circuit 1 that is applied to the reference voltage input terminal Vr of the analog-to-digital converter 5 during transport operation.
This is a correction section that acts to correct the output voltage value of No. 9 using the average value C of the measurement errors calculated in the above-mentioned balancing state.

In addition, the average value C of the weighing error calculated in the calibration state
A control circuit (not shown) is configured to store the counter 14 and totalizer 16 in preparation for the next balancing. Span adjustment is performed as follows.

After the zero point adjustment is completed and during no-load operation, the instantaneous weight Q is simulated in the load conversion section 3 by the balancing device 9.

Load. In this balancing state, the transportation amount accumulator 7 stops the accumulation operation until the balancing is completed, and the counter 14 and totalizer 16 start operating. In the analog-to-digital converter 5 of the load conversion device 6, assuming that the output of the load cell 3 during normal span is A=E, and the voltage applied to the reference voltage input terminal Vx during normal span is ■Ref=Eref, digital conversion is performed. Therefore, the output of the subtractor 13 becomes the weight value 0.

However, as mentioned above, for example, due to the span variation of the load cell 3b and the belt thickness variation, even in the balanced state, the unknown voltage input terminal V of the analog-to-digital converter 5
The load cell 3b output voltage supplied to x changes to . The integrator 16 integrates the span variation Δg=Eα obtained via the subtractor 13 while the belt 2 rotates n times. The output of the arithmetic circuit 17 obtained by processing the cumulative value A of the totalizer 16 using the first equation when the belt 2 reaches n rotations is sent to the correction unit 18 as the output voltage E of the reference voltage generation circuit 19.
During the conveyance operation, the analog-to-digital converter 5 acts to correct ref, and during the next conveyance operation with the span of the load cell 3b changed, assuming that the output voltage of the load cell 3b at that time is E°, the analog-to-digital converter 5 Calculations are performed, and the effect of span changes on the total transport volume can be avoided by simple operations.

In addition, in the above embodiment, the span change of the load cell 3b was explained as an example, but the span change of the analog-to-digital converter 5 and the amplification factor of the amplifier interposed between the load cell 3b and the analog-to-digital converter 5 are also explained. Changes in can also be corrected in the same way.

Further, in the above embodiment, the correction means is configured to correct the voltage applied to the reference voltage input terminal Vr of the analog-to-digital converter 5 based on the average value C of the calculated weighing errors. The same effect can be obtained by configuring the output of the analog-to-digital converter 5 to be corrected based on the calculated average value C of measurement error. As configured as described above, the span adjustment device for the belt scale of the present invention can automatically calculate the average value of the weighing error due to the span change by setting the balance state during no-load operation of the Bell I scale. The output of the load conversion device can be corrected during the next transport operation using the average value of the calculated weighing errors, and the influence of the span change of the load conversion device 6 on the calculation of the total transport amount can be avoided. , which allows for highly accurate measurement.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an embodiment of a belt scale equipped with the span adjustment device of the present invention, FIG. 2 is an explanatory diagram of the load conversion device in FIG. Fourth
The figure is an explanatory diagram of span change. 10*・I belt conveyor, 20-...belt, 3・
1 Load converter, 4...Pulse transmitter, 5...
...Analog to digital converter, 6...Load converter, 9...Balancing device, 10...
First setting device, 11...Second setting device, 13.
... Subtractor [first arithmetic device], 14 ... Counter, 15 ... Coincidence detector, 16 ...
- Totalizer [second arithmetic device] 17...Arithmetic device, 18...Correction unit.

Claims (1)

[Claims] 1 The instantaneous transport amount on the working length of the endless belt for transport is
In a belt scale that is configured to calculate from a conveyance speed and an instantaneous weight value, continuously integrate the instantaneous conveyance amount, and display the total conveyance amount, no load is applied to the load conversion device that detects the instantaneous weight value. a balancing device that can simulate a constant instantaneous weight during operation; and a balancing device that subtracts the constant instantaneous weight value from the output of the load conversion device during no-load operation and in a balanced state in which the balancing device is activated. The first arithmetic device detects that the endless belt-shaped body for conveyance has rotated by a predetermined value, and calculates the integrated value of the output of the first arithmetic device from the start of the calibration, the predetermined number of rotations, and the operation for the entire circumference of the endless belt-like body. A second arithmetic device that calculates an average value of weighing error due to a span change from a long number, and a correction means that corrects the output of the load conversion device during conveyance operation using the output of the second arithmetic device. Features: Span adjustment device for belt scales.