JPS5927849B2 - Digital display scale control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a control circuit in an electronic circuit related to a digital display device of a weight scale.

This application was previously filed as a utility model for a mechanism in which an electrode plate composed of two parallel plates moves the distance between the parallel plates in response to body weight, thereby detecting the displacement of the capacitance ( Application number 52-021061) has been completed.

This is a weight scale control circuit that uses this change in capacitance as an oscillator element to make the oscillation frequency proportional to the weight and digitally display it. Instead of the conventional method of visually checking the weight using a fixed scale plate and a rotary pointer that rotates in response to the body weight, or a rotary scale plate that rotates in response to the body weight, a new method that digitally displays the weight is now available. One of the proposed methods is a digital scale that uses a differential transformer and a strain gauge as a sensor, which measures the displacement (voltage) equivalent to the body weight.
is converted to digital via an A/D converter, and in order to maintain the linearity of the output voltage with respect to the body weight of these sensors, the linearity is corrected by adjusting the mechanism that transmits the weight of the body weight to the sensor. This made the equipment complicated and difficult. In addition, the zero point must be adjusted mechanically, which complicates the manufacturing process and reduces reliability and price.
The figure is a timing chart showing the operation of the present invention. When the power-on switch 9.2 of the power supply circuit 9 is manually turned ON, battery power is applied to the DC-DC converter 9.3, and a high voltage (hereinafter referred to as H level) is applied to the base of the switching transistor TRl. TRl becomes 0N, reed relays 9 and 4 are set to 0N, and the power-on switch is turned on.
Even if it is FF, after that a low voltage (hereinafter referred to as L) is applied to the base of TRl.
The power supply circuit will not turn off unless a voltage (referred to as a level) is applied. When power is applied to each block circuit, the C terminal of the counter Z2 counts the clock pulses output from the D of the counter Z2 for a certain period of time T1 according to the timing chart shown in FIG. goes high at the rising edge of the output pulse of counter Z2, Q of the F2 circuit goes low, and the load register terminal 11. of the integrated circuit 11 goes to the high level. e becomes L level and the clock counter 11. The initial value (no load) frequency F of the oscillator 1 corresponding to the weight input to a. of,
At the same time as the storage in the register circuit 5 is completed, F
The Q output of the two circuits becomes H level and NAND gate 2.1
and 2.2 to the clear terminal 11. of the integrated circuit 11. b
becomes L level, the display circuit section 7 displays 0.0 and is set to prepare for weight measurement. Next is C, which has a capacity of 1.1 in response to body weight.

When a body weight is applied to the oscillator 1, the oscillation frequency f corresponding to the body weight is transmitted to the clock counter input terminal 11 of the integrated circuit 11. input to a. Then, the frequency F whose initial value (no load) frequency is stored in the register circuit 5. At the point in time (point a in Fig. 3), the equal terminal 11. A pulse indicating a match is output from f, and the F3 circuit Q output goes to L level and NAND gate 2
．． Counter 3 included in integrated circuit 11 via 3
Talia's contents. After that, as shown in the timing chart in Fig. 4, the count inhibit pulses T2 and T3 are generated from the binary outputs B and C of the counter Z2 via the NOR gate 2.3, and the D output of the counter Z1 and the A output of the counter Z2 are output. and count inhibit pulse NAN
A store pulse is formed through the D gate 2.4 circuit, and only the frequency Δf corresponding to the body weight is displayed on the display section 7, and the frequency F is the frequency when the body weight is not present. is removed from the frequency knob f on which the weight is applied, and the frequency Δf of only the weight is digitally displayed.

When the measurement is completed and the weight remains unchanged (zero state), the BCD output terminal group 11. of the integrated circuit 11. are all L level, and H level data is input to the D input of the F5 circuit (!11.F6 circuit) via the NOR circuit 8.
The contents of D (H level) of the F5 and F6 circuits are transferred to Q by the timing pulse of the digit, respectively, and the NAND gate 8.
Counter circuit Z4, Z5 through 2 set terminal R
is maintained at L level.

Therefore, counters Z4 and Z5 start counting the clock pulses of D of counter Z2, and after counting for a certain period of time, the clock terminal CL of counter Z4 and the clock pulse of counter Z5 are counted.
The output connected to the B terminal of the binary output becomes H level and passes through the NOR gate circuit 8.3.As explained above, the base of the switching transistor TRl becomes L level and is turned off, turning the reed relay 9.4 off. The power supply voltage is cut off and the entire system is turned off to complete the measurement. As described above, the present invention is configured as an oscillator that converts the object to be measured (body weight) into capacitance changes of two parallel plates, and displays this digitally.
The nonlinearity in stray capacitance C8 caused by the capacitance conversion mechanism corresponding to the body weight can be easily counted using an electronic circuit by using the correction capacitor C of the oscillator 1. It can be corrected, and by adjusting the oscillation frequency with Polyuum VRl, it can be displayed in units of kg, pounds, etc. using the same mechanism of the scale, and in the past, zero adjustment was required before measurement. However, in the present invention, the power-on reset circuit when the power is turned on sets the initial value of no load, and from that point on, only the body weight is measured and displayed, so zero adjustment is unnecessary. After the measurement is completed, the power is automatically turned off by the automatic power-off circuit.It is extremely easy to operate, and since all the circuits are made of C-MOS with extremely low power consumption, it can be sufficiently powered by batteries. It maintains a long lifespan and is portable at the same time.

In addition, in the manufacturing process, the adjustment section (zero adjustment, linearity) can rely solely on the electronic circuit section, which greatly reduces the setup time and allows for high-precision, highly reliable digital display suitable for mass production, making it practical. This is an effective invention both physically and technically.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a process diagram of the present invention. FIG. 2 is a specific circuit diagram based on the program diagram of FIG. 1. 3 and 4 are timing charts for explaining the operation of the present invention. 1...Oscillation circuit section, 1.1...Two parallel flat plates, 12.
...Measuring spring, Cp... Compensation capacitor 1, VRl... Frequency adjustment polyurethane, 2... Gate circuit section, 3... Counter circuit section, 4... Gate clock circuit section,
5...Register circuit section, 6...Comparator circuit section, 7...Display section, 8...
...Zero detection circuit section, 9...Power supply circuit section, 10.
... Reset circuit section, Z, ~Z2 ... Counter, F1 - F6 ... Flip-flop circuit, 0P1 - 0P2 ... Arithmetic amplifier, 9. 4/
...Reed relay, 9.3...DC-D
C converter.

Claims (1)

[Claims] 1. Two operational amplifiers O are included in an oscillation circuit 1 that generates as an electrical output a frequency that changes as the polar capacitance Co between a movable electrode plate that moves according to weight and a fixed electrode plate changes.
P_1 and OP_2 are provided, the capacitance Co is connected between the input and output of the second operational amplifier OP_2, and the first
A first resistor R_1 is connected between the input and the output of the operational amplifier OP_1, and a second resistor R_1 is connected between the output of the second operational amplifier OP_2 and the input of the first operational amplifier OP_1.
resistor R_2 is connected, and the first operational amplifier OP_1
A third resistor R_3 and a correction capacitor Cp are connected between the output of the oscillation circuit 1 and the input of the second operational amplifier OP_2, and the frequency of the electrical output of the oscillation circuit 1 is directly counted to calculate the weight. , a digital display circuit 7 for displaying the count from the counter circuit, and a power supply circuit 9 for the oscillation circuit 1, the counter circuit 3, and the display circuit T. A control circuit for a digital display scale featuring: 2 First resistor R_1 and second resistor R_ of oscillation circuit 1
2. The control circuit for a digital display scale according to claim 1, wherein the oscillation frequency of the partial pressure ratio of 2 is changed by a volume VR_1, and the weight can be switched in kg or pound units. 3 The power supply circuit 9 is powered on for a certain period of time after the weight measurement is completed.
A control circuit for a digital display scale according to claim 1, further comprising means for automatically turning off this power supply circuit when a no-load state continues.