JP2768534B2 - Load measuring device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a load measuring device that converts a weighing signal into a digital signal and outputs the result.

2. Description of the Related Art Even if the load is detected by a load converter having an analog output, the load is often converted into a digital signal for signal processing in a subsequent stage. With a general electronic scale,
As shown in FIG. 3, an object 1 is loaded on a load cell 2, and an output signal of the load cell 2 is applied to an unknown input of a double integration type A / D converter 5 via an amplifier 3 and a low-pass filter 4 so as to be digitalized. Has been converted.

Problems to be Solved by the Invention The double integral type A / D converter 5 is widely used for electronic scales, but in the field of measuring the load of an object to be weighed during high speed transportation by a belt conveyor, Since high-speed digital conversion cannot be realized, it is very difficult to use the conventional double-integration A / D converter.

Furthermore, even if high-speed digital conversion can be realized,
In order to obtain the peak value of the weighed value, it is necessary to perform repeated arithmetic calculations.

The present invention can measure the load of the object to be weighed during high-speed transportation even if the overall operation speed is slow, and furthermore, when trying to find the peak value of the weighed value, it is not necessary to perform repeated arithmetic calculations. An object is to provide a load measuring device.

Means for Solving the Problems A load measuring device according to the present invention includes a comparator that compares an analog weighed signal level with a reference signal level to determine the level of the analog weighed signal, and a clock based on the determination of the comparator. Providing a reversible counter for selecting up-count and down-count, and a D / A converter for converting the digital output of the reversible counter into analog,
An analog output of the converter is connected to the comparator as a reference signal, and a digitally converted output of a weighed signal is obtained from a digital output of the reversible counter.

According to this configuration, the level of the analog weighing signal is compared with the reference signal level by comparing the level of the analog weighing signal with the reference signal level obtained by converting the current count value of the reversible counter into analog by the D / A converter. If the comparator determines that it is greater, the reversible counter counts up the clock, and if the comparator determines that the level of the analog weighed signal is less than the reference signal level, the reversible counter counts down the clock. Therefore, the content of the reversible counter at each time becomes a digital value corresponding to the weighed value.

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 shows a main part of a weight integrator for a belt conveyor employing the present invention. The load received by the weighing conveyor 8 interposed between the conveyors 6 and 7 is detected by the load cell 2,
Comparator 9 via amplifier 3 and low-pass filter 4
Is compared to the level V _R of the reference signal 10 is applied to the non-inverting input of the (+). Set the output level of low-pass filter 4 to V _S
When the output side T ₁ of the comparator 9 is "V _R> V _S" of the inverted logic level "H" when the output side T ₂ are "V _R <V _S" logic level when the "H" Flip to Here the output side T ₁ of the comparator 9 is connected to the instruction to the + terminal to perform up-counting of the control terminals of the reversible counter 11, the output side
T ₂ instructs the execution of the down-counting of the reversible counter 11 - is connected to the terminal.

The reversible counter 11 is a clock that is repeatedly output from the pulse oscillator 12 when the + terminal is at the logic level “H”.
CK is counted up, and the clock CK is counted down when the-terminal is at the logic level "H".

The count content of the reversible counter 11 is converted into an analog signal by the D / A converter 13, and the inverted input (−) of the comparator 9 is output.
Is applied as a reference signal 10.

As shown in FIG. 2, a weighing signal having a fluctuation cycle t as shown in FIG. 2 is applied to the non-inverting input (+) of the comparator 9, and the repetition frequency of the clock CK is f and the resolution of the load integrator is a.
It is set as follows.

f ≧ (a / t) With this configuration, the count value of the reversible counter 11 at each time is shown in FIG. 2 without executing high-speed sampling as in the conventional double integral type A / D converter. The digital output of the weighing signal is obtained from the output of the reversible counter 11, and the weight of the transported weight is calculated based on the count value of the reversible counter 11 in a subsequent signal processor (not shown). Is measured, and this is integrated to calculate the total transported amount.

Further, when the peak values P ₁ , P ₂ ,... Shown in FIG. ₂ are obtained, the output side T ₁ or T ₂ of the reversible counter 11 is monitored, and the reversible counter 11 at the timing when the logical level is inverted is monitored. It is only necessary to read the count value of, and there is no need to arithmetically compare the digital output values as in the conventional case.

In the above embodiment, the case of the weight integrator has been described as an example. This is effective for an object that needs to measure a moving object, such as a weight checker configured to switch the discharge path.

As described above, according to the present invention, a comparator that determines the level of an analog weighed signal by comparing an analog weighed signal level with a reference signal level, and counts up a clock based on the determination of the comparator And a reversible counter whose down count is selected, and a D / A converter for converting the digital output of the reversible counter into an analog signal, so that the counting operation of the reversible counter is controlled by the output of the comparator. Even if it is slow, the load value of an object moving at a high speed can be converted into a digital value.

Also, when trying to find the peak value of the weighed value,
It is only necessary to monitor the output side of the reversible counter and read the count value of the reversible counter at the timing when the counting operation switches from counting up to counting down or vice versa, and it is necessary to arithmetically compare the digital output value as in the past. And the configuration can be simplified.

[Brief description of the drawings]

FIG. 1 is a main part configuration diagram of a weight integrator for a belt conveyor as one embodiment of a load measuring device of the present invention, FIG. 2 is a waveform diagram of the main portion of the device, and FIG. It is a block diagram. 2 ... Load cell, 9 ... Comparator, 10 ... Reference signal, 11 ... Reversible counter, 13 ... D / A converter.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01G 23/37-23/375 G01G 11/00

Claims (1)

(57) [Claims] 1. A comparator for comparing a level of an analog weighed signal with a reference signal level to determine a level of the analog weighed signal, and a reversible circuit in which up-counting and down-counting of a clock are selected based on the judgment of the comparator. A counter and a D / A converter for converting the digital output of the reversible counter into an analog signal are provided.The analog output of the D / A converter is connected to the comparator as a reference signal. Load measuring device that obtains converted output.