JPH025389Y2 - - Google Patents

Description

[Detailed explanation of the idea] This invention relates to electronic balances.

Conventional analog output methods for electromagnetic balance balances include converting the current that generates electromagnetic force into voltage and extracting it, or using D/A to output digital data.
There was a method to introduce it into the converter and take it out. However, in the method of converting to voltage and extracting it, the accuracy of the balance is 1/20000, but the accuracy of the connected recorder is usually 1/20,000 due to the relationship between the width of the recording paper and the amount of displacement that can be read from the recorded result. /200 or at most 1/500, so if you try to record legibly to the same precision as the balance, that is, to the same minimum measurement unit as the balance, the recorder will overscale. On the other hand, if you try to record the balance output without overscaling, it will become virtually impossible to record minute changes in the balance output. Therefore, in order to record with the same accuracy as the balance without overscaling, it is necessary to take measures such as subtracting a known voltage from the balance output as appropriate according to changes in the balance output before inputting it to the recorder. It didn't happen. Also, D/A
In the system using a converter, the D/A converter used is about 8 to 10 bits, whereas the balance output is 20 bits or more, and therefore has the same drawbacks as described above. Furthermore, the analog output method, in which a switching circuit is provided to connect to the balance's digital output line corresponding to the analog range required for the input signal to the D/A converter, has the disadvantage of a complicated structure and high cost. Ta.

This invention solves the above-mentioned conventional drawbacks, has a simple structure, and allows you to freely select the balance range you need.
Moreover, it is possible to obtain an analog output obtained by D/A converting the digital data output corresponding to the range. The purpose is to provide electronic balances.

In order to achieve the above object, this invention uses an electromagnetic force self-balancing balance that has a changeover switch that changes the function of the tare switch and a D/D/D/D/D/2 switch that has a smaller number of input digits than the number of digits of the digital output section of the balance.
A converter, and each time the tare switch is operated, the input range of the D/A converter changes to at least 1.
It is characterized by being configured to move digit by digit.

Hereinafter, embodiments of this invention will be described based on the drawings.

The drawing is a block diagram showing the configuration of the electromagnetic balance type balance according to the above embodiment.

In front of the pole 2 supported at the fulcrum 1 are a plurality of weights (not shown) having different masses from the sample plate 3.
is weighted, and an electromagnetic device 4 that applies force to the pole 2 is provided behind the pole 2 to adjust the balance of the pole. The electromagnetic device 4 mainly consists of a magnet and a feedback coil. Further, a position detection section 5 for detecting the balance state is provided at the rear of the pole 2. PID
The amplifier 6 is an amplifier circuit that receives the detection signal from the position detection section 5 and supplies current to the feedback coil until the balance is in a balanced state during measurement. The A/D converter 7 converts the analog electrical signal of the current flowing through the feedback coil into an A/D converter.
This is a converter that converts signals into digital signals. A central processing unit (CPU) 8 is a control unit that receives the digital output of the A/D converter 7, detects weighing data, and controls the current supplied to the feedback coil. , a display 9, and a data latch circuit 10, and is further provided with a tare switch S1 and a changeover switch S2. When the switch S2 is set to the A side, it instructs the CPU 8 to perform normal balance measurement, and the B
When set to the side, this switch instructs the CPU 8 to turn the tare switch S1 into a D/A conversion input range setting switch. Tare switch is switch S
2 is the switch used to instruct the balance to tare when set to the A side. The data latch circuit 10 is a circuit that temporarily stores the input of the D/A converter 11. Outputs analog conversion signal. Each time the changeover switch S2 is set to the B side and the tare switch S1 is operated, the D/A
The range of the signal input to the converter 11 moves by one digit. That is, the D/A converter 11 inputs the bit signal from the data latch circuit 10 to a predetermined bit input terminal, weights it according to each input bit, and converts it into an analog signal. Since the number of bits of the A converter 11 is smaller than the number of bits of the balance, a part of the number of bits stored in the data latch circuit 10 is input. Then, when the changeover switch S2 is set to the B side and the tare switch S1 is operated, the data latch circuit 10
The bit signal supplied to each bit input terminal of the D/A converter 11 is shifted in a predetermined direction from the previous one, and as a result, a different bit signal from the previous one is supplied to each bit input terminal. In other words, the D/A conversion input range will be moved. In addition, such D/A
The conversion input range is moved when the CPU 8 detects that the tare switch S1 has been operated.
This is done through software processing.

Next, the operation of the above embodiment when extracting the balance digital output as an analog output will be explained.

When switching the D/A conversion input in order to prevent the extracted analog output from overscaling on the recorder 12, switch S2 is switched to the B side to change the balance measurement state to the D/A conversion input range setting. At that time, tare switch S1 is set to D/A.
This is an input switch that moves the conversion input within the balance range. Here, if the upper limit of the balance's data range is 200000g, then BCD (binary coded decimal)
While 22 bits are required for digital output, a D/A converter 11 with an input bit count of 10 is used. Therefore, when the tare switch S1 is pressed once, the input range of the D/A converter 11 moves one digit at a time, and the display 9 displays not the balance data but the moved amount or the D/A input range. .

When the setting of the D/A conversion input range is completed in this way, the switch S2 is returned to the A side and the balance operation is restarted. The analog output from the D/A conversion input set above can be taken out at fixed time intervals or by arbitrarily issuing an external data output request signal RS to the CPU 8.

As described above, according to this invention, it is possible to obtain an analog output by moving the input bit position of the D/A converter from the maximum digit to the minimum digit position of the output of the digital balance using the tare switch. It can also be used in recorders without a digital balance, and since it has a simple configuration and uses a D/A converter with a small number of bits, an inexpensive electronic balance can be obtained.

[Brief explanation of drawings]

The drawing is a block diagram showing the configuration of an embodiment of this invention. DESCRIPTION OF SYMBOLS 1... Fulcrum, 2... Saddle, 3... Sample plate, 4... Electromagnetic device, 6... PID amplifier, 7... A/D converter, 8... Central processing unit, 9... Display, 10... Data latch circuit, 11... D/A converter, S1... tare switch, S2... changeover switch.

Claims (1)

[Scope of utility model registration request] In an electromagnetic force automatic balance balance equipped with a digital output section that displays the load and a tare switch that instructs tare subtraction, there is a changeover switch that changes the function of the tare switch, and a number of input digits smaller than the number of digits of the digital output section. and a D/A converter, the electronic balance being configured such that the input range of the D/A converter moves by at least one digit each time the tare switch is operated.