JPS584776B2 - Digital Hakarino Zero Ten Hoseihouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for correcting the zero point of a scale that obtains a voltage proportional to weight and displays it digitally.

Even if a digital scale displays zero when there is no load, deviation of the zero point within the minimum display unit weight can be a cause of measurement error.

Conventionally, zero point correction in this type of digital scale has often been carried out by increasing or decreasing the output voltage of the scale using a variable resistor or the like while visually checking the display.

However, even if the value is visually corrected to zero, there is a wide range between the zero in the positive area and the zero in the negative area, and it is difficult to correct the value to a true zero.

Here, a circuit that amplifies the output of the measuring instrument several times is installed, and the output voltage is amplified several times during zero point correction to perform the same operation. Also, by feeding back the output voltage of the measuring instrument, the resolution of the display can be improved. It is possible to bring the output voltage of the measuring instrument closer to zero in a width smaller than the width of Therefore, satisfactory results cannot be obtained with these methods.

The object of the present invention is to quickly correct the zero point deviation of the measuring instrument and the zero point deviation of the A/D converter with a resolution higher than that of the display.

The configuration of the present invention will be explained below based on the drawings.

1 is a measuring device that uses a transducer such as a differential transformer to generate a voltage proportional to the weight of the item, 2 is a subtraction circuit, and 3 is a double integral A/D converter that generates a number of pulses proportional to the voltage. 4 is a pulse frequency divider, 5 is a counter, 6 is a data latch circuit, 7 is a display section, 8 is a gate, 9 is a reversible counter, and 10 is a D/A converter.

The voltage output from the meter 1 and the voltage output from the D/A converter 10 are used by a subtraction circuit 2 to provide the difference between the two voltages to the A/D converter 3.

If a differential input type A/D converter is used here, the subtraction circuit 2 is omitted.

The A/D converter 3 generates a number of pulses a proportional to the difference between both voltages at regular intervals, and also generates a polarity signal C and a pulse a.
A reset signal d is output immediately before PALNU a, and a latch signal e is generated immediately after PALNU a.

The frequency divider 4 divides the frequency of the pulse a to generate a pulse b determined by the minimum display unit weight.

For example, if the full scale of a scale is 1 kg, the output voltage is IOV for 1 kg, and the minimum display unit weight is 1 g, the A/D converter 3 will output 10,0 for a voltage of 10 cm.
If 00 pulses a are generated, the frequency division ratio is set to 10:1 in order to generate one pulse b for every 1 g.

Counter 5 counts pulses b after being set by reset signal d, and its value is latched in data latch circuit 6 by latch signal e.

The display section 7 displays the output data of the data latch circuit 6 numerically, and also displays the polarity using the polarity signal C.

A/D conversion is performed at a constant cycle, and even if the output voltage of the meter changes, the display is maintained for one cycle, and the operation of displaying the skewer data of the counter 5 is repeated in the next cycle.

Here, it is assumed that m pulses a are output when the measuring instrument is unloaded.

If the frequency division ratio is n:1, the pulse b becomes m/n and the fractions below the decimal point are discarded, so when m<n, the display is zero.

The gate 8 is opened by applying a correction command signal f from the outside, and the pulse a is connected to the reversible counter 9.
The conversion coefficient of the A converter 10 is, if the output voltage of the measuring instrument at full scale is Emax (V) and the number of pulses a at that time is mmax (pieces), then for one pulse a, Emax
The output voltage is set to be slightly lower than x/mmax (V).

The D/A converter 10 generates a voltage proportional to the output of the reversible counter according to the coefficient, and the voltage applied to the A/D converter changes.

In the next cycle, the number of pulses a becomes less than m, and the number of pulses a at that time is cumulatively counted again.

By applying the correction command signal f until the number of pulses a becomes O, the zero point is corrected to 1/n of the minimum display unit weight.

In the example mentioned above, if the minimum display unit weight is 1g, it is ±0.
Zero points are corrected up to 1g.

When the correction command signal f is not given, the output data of the reversible counter 9 is held, that is, the D/A converter 10
The output voltage of is maintained.

As is clear from the above explanation, by feeding back and correcting the data after A/D conversion, the zero point deviation of the measuring instrument and the zero point displacement of the A/D converter are corrected together.
By detecting the pulses before dividing the count pulse required for display, correction can be made with a resolution higher than that of the display, and furthermore, the correction operation can be performed quickly because only a signal is applied by an external switch, etc. can achieve the desired purpose.

The zero point correction range in a digital scale is sufficient within 0.5 factor relative to the full scale, but by increasing the range, it can also be used for tare subtraction.

It is also possible to input the weight signal from the data latch circuit 6 into the charge calculation circuit, calculate the weight signal and the unit price input, and display the charge.

As explained above, the present invention includes a measuring device that uses a transducer such as a differential transformer to obtain a voltage proportional to the weight of an article, an A/D converter that obtains a number of pulses proportional to the voltage, and a device that counts pulses. In a digital scale consisting of a counter and a display section, the number of output pulses from the A/D converter is multiplied by the number of pulses required for display, and a reversible counter that cumulatively counts the number of pulses and a D/D/D/D converter that obtains a voltage proportional to the output of the reversible counter. An A converter is provided, and the output voltage of the measuring instrument and the D/A converter are provided.
By feeding the difference between the output voltage of the converter and the output voltage to the A/D converter again, the zero point correction is performed with a resolution higher than that of the display, so the advantage is that the zero point correction of this type of digital scale can be easily and accurately performed. There is.

[Brief explanation of drawings]

The drawing is a block diagram of a method for correcting the zero point of a digital scale according to the present invention. 1... Measuring instrument, 2... Subtraction circuit, 3.
...A/D converter, 4...Pulse frequency divider, 5...Counter, 6...Date latch circuit, 7... Display section, 8...Gate, 9...Reversible counter, 10...
D/A converter, f... Correction command signal.

Claims (1)

[Claims] 1. A measuring instrument that uses a transducer such as a differential transformer to obtain a voltage proportional to the weight of an item, an analog digital converter (hereinafter referred to as an A/D converter) that obtains a pulse number proportional to the voltage, and a pulse In a digital scale consisting of a counter and a display section, the number of output pulses from the A/D converter is multiplied by the number of pulses required for display, and a reversible counter that cumulatively counts the pulses and a voltage proportional to the output of the reversible counter are used. A digital-to-analog converter (hereinafter referred to as D)
/A converter) is provided, and the output voltage of the measuring instrument and D
1. A method for correcting a zero point of a digital scale, characterized in that the difference between the output voltage of the A/D converter and the output voltage of the A/D converter is applied again to the A/D converter to perform zero point correction with a resolution higher than that of the display.