JPS623893B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a measuring instrument, and particularly to a measuring instrument having a structure in which the weighing platform is rotated.

In recent years, devices have been developed that include a built-in digital measuring device in a microwave oven and control heating according to the weight of the food to be cooked. Generally, in such a measuring instrument,
A tray in the microwave oven is used as a weighing table, and the weight applied to the tray is converted into the displacement of the cantilever.Then, this displacement is converted into an electric signal using a potentiometer, strain gauge, etc., and after A-D conversion, it is converted into a digital signal. A display method is used. On the other hand, in microwave ovens, in order to prevent uneven cooking due to standing electromagnetic waves, a structure has been devised in which a saucer is provided with a rotating mechanism to heat the food while rotating it.
FIG. 1 shows an example of this, in which numeral 1 denotes a weighing table on which food is placed, and a central shaft 2 is connected to a motor M to rotate. 3 is a roller disposed between the fixed plate 4 and the weighing table 1 via a spring 5, and the tip of the support shaft 6 of one roller 5 comes into contact with the vicinity of the tip of the cantilever 7 attached to the fixed plate 4. ing. This cantilever 7 therefore bends downward in response to the weight applied to the weighing platform 1. 8 is a magnetic piece attached to the tip of the cantilever, and 9 is a magnetic sensor placed close to this magnetic piece. In a weighing instrument equipped with such a rotation mechanism, if weighing is performed while the weighing platform 1 is rotating, unnecessary force and vibration caused by the rotation will be applied to the weighing platform 1, resulting in a larger error than the measured value when it is stationary. The disadvantage is that only measured values can be obtained. In addition, this error constantly changes due to vibrations, etc., so the display, especially the lowest digit, flickers to the point that it is almost unreadable, causing anxiety to the user and making it impossible to read the approximate weight. A situation may arise. Figure 2 shows the change in the weight value when a 200g object is actually placed on the rotary weighing table as described above and weighed.The vertical axis shows the number of grams displayed, and the horizontal axis shows the time. It takes (seconds). As shown in the figure, it can be seen that the weight oscillates up and down within a range of about 5 g around the weight of 200 g.

The present invention solves the above-mentioned drawbacks and is as follows:
An example will be described using figures. 9 in the figure indicates 2 connected in series to the magnetic pole surface of the magnet 10 in the magnetic sensor.
magnetoresistive elements m ₁ m ₂ are fixed. This magnetoresistive element m ₁ m ₂ is made of a high mobility semiconductor such as InSb or InAs, and one end is connected to a low voltage source V (approximately 5 V).
The other end is grounded, and the output signal is taken out from the intermediate point. This magnetic sensor 9 outputs an electric signal corresponding to the amount of displacement of the magnetic piece 8 attached to the cantilever 7 which bends in accordance with the weight applied to the weighing platform 1. Reference numeral 11 denotes an operation amplifier which takes the output of the magnetic sensor 9 as one input, and adds a potential obtained by dividing the low voltage source V by a resistor r ₁ r ₂ to other inputs as a reference potential. The A-D converter receives an analog signal output from the amplifier 11 and converts it into a digital signal, and outputs a digit signal D ₁ D ₂ D ₃ and numerical signals Q ₀ to _{Q 3} . A ₀ ~ _{A 3} are numerical signals Q ₀ Q ₁ Q ₂ Q ₃ respectively
is an AND gate with one input as one input, OR1 is an OR gate with digit signal D ₁ D ₂ D ₃ as input, and digit signal D ₃
Enter via Switch _S2 . This switch
S ₂ has terminals a and b, and terminal a is an OR gate.
Terminal b is grounded to the input of OR1. The output signal of the above OR gate OR1 is the AND gate A ₀ ~ _{A 3}
is applied to the other input terminal of Numerical signals _Q0' to _Q3' corresponding to the numerical signals _Q0 to Q3 are input to a decoder ₁₃ to which the outputs of the AND gates _A0 to _A2 are added. 14 is a display drive circuit to which the numerical signal converted into a decimal number by the decoder 13 is applied;
15 is a display device consisting of a display element such as a fluorescent display tube, LED, or LCD, and in this case, it consists of a three-digit number. Here, the digit signal from the A-D converter 13 is
D ₁ D ₂ D ₃ is input to the display device 15 as a digit selection signal. M is a motor that rotates the weighing platform 1, to which 100 V AC is applied via a power switch _S1 . Here, this power switch _S1 is configured to interlock the above-mentioned switch _S2 , and when the power switch _S1 is open, the switch _S2 is in contact with the terminal a side, and when the power switch S1 is closed, the switch _S2 is in contact with the terminal a side. Switch _S2 is switched to terminal b side.

Next, the operation of the above configuration will be explained. First, weighing platform 1
When the motor M is at rest, the power switch _S1 of the motor M is in an open state, so the switch _S2 is located on the terminal a side. Therefore, the amount of displacement of the magnetic piece 8 detected by the magnetic sensor 9 is
input to the A-D converter 12 through the digit signal D ₁
~D ₃ and numeric signal Q ₀ ~Q ₃ occur, digit signal D ₁
Numerical signals Q ₀ ~ _{Q 3} are AND gated in synchronization with ~D ₃
It is input to the decoder 13 through A ₀ to A ₃ . Note that the digit signal D ₁ is the most significant digit signal, and D ₃ is the least significant digit signal. The numerical signal converted into decimal by the decoder 13 is input to the display drive circuit 14, which is driven to display a predetermined weight on the display device 15. In other words, in the case of the numerical signals Q ₀ to _{Q 3} shown in Fig. 5, 345
g will be displayed.

Next, close the motor power switch S ₁ and weigh the weighing platform 1.
When starting to rotate, the switch _S2 switches to the terminal b side in conjunction with the power switch _S1 , and the digit signal _D3 is not input to the OR gate OR1, so at this timing, the AND gate A ₀ to _A3 are closed. Therefore, at the timing of the digit signal _D3 , the outputs of the AND gates _A0 to _A3 all become zero, and the least significant digit display on the display device 15 is fixed at "0". In other words, in the case of the above numerical signal, the display is
It will be 340g. In this way, the lowest digit is fixed to the display "O", so even if the weighing value of the lowest digit changes within the range of 1 to 9 g due to vibration of the weighing platform, the display on the display device 15 will not change. .

FIG. 4 shows another embodiment of the present invention, in which the display of the lowest digit is fixed to either "O" or "5" while the motor is driving. To explain using the same figure below, OR ₂ is an OR gate with two inputs of numerical signals Q ₂ Q ₃ , A ₄ is an OR gate with one input terminal connected to terminal b of switch S ₂ , and the other input terminal connected to the OR gate. The AND gate OR ₃ connected to the output of the AND gate _{A 2} is an OR gate having two inputs each of the outputs of the AND gates A ₀ and A ₄ , and its output is input to the decoder 13 as a numerical signal Q ₀ '. _OR4 is an OR gate having two inputs, each output of AND gates _A2 and _A4 , and its output is input to the decoder 13 as a numerical signal _Q2 '. In the figure,
The other circuit parts are the same as those in the embodiment shown in FIG. 3, so their explanation will be omitted. In such a configuration, when the motor is not driven, an accurate three-digit numerical value is displayed, as explained in the above embodiment. On the other hand, when driving the motor, if the numerical signals Q ₀ to Q ₃ are 0 to 3 in decimal notation, the decoder 13 input signal
Q ₀ ′ to Q ₃ ′ are (0000) and the display is “O”.
Further, when the numerical signals Q ₀ to Q ₃ are expressed in decimal notation and number 4 to 9, Q ₀ ' to Q ₃ ' become (1010) and the display becomes "5". In other words, in the case of the numerical signal shown in Figure 5, the lowest digit changes and the weight value changes from 340 to 343 g.
When it is in the range of , the display will be 340g, which is 344 to 349
g, the display will be 345g.

In the other embodiments described above, when the least significant digit is 3 or less, it is displayed as 0, and when it is 4 to 9, it is displayed as 5, but this has the advantage that it can be realized at low cost because it has a relatively simple gate configuration. However, in addition to this, rounding up the least significant digit, rounding to the nearest whole yen, etc. can also be realized in the same way.

As described above, the measuring instrument of the present invention fixes the display of the lower digits, especially the lowest digit, to a specific value such as "O" or "5" while the weighing platform is being rotated by the motor. This eliminates the flickering and difficulty in reading the display caused by the weighing value constantly fluctuating up and down as the weighing table rotates as in the past, and provides an easy-to-read display without causing discomfort to the user.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view of a measuring instrument having a rotary weighing platform, FIG. 2 is a diagram showing the fluctuation of measured values by the above-mentioned measuring instrument, and FIG. 3 is a block diagram of an embodiment of the present invention.
FIG. 4 is a block diagram of another embodiment, and FIG. 5 is a signal waveform diagram for explaining the operation of the above embodiment. 1... Weighing stand, 3... Roller, 7... Cantilever, 8... Magnetic piece, 9... Magnetic sensor, 10...
...Magnet, 11...Operation amplifier, 12...
... A-D converter, 13 ... decoder, 14 ... display drive circuit, 15 ... display device, M ... motor,
_S1 ...Motor power switch, _S2 ...Switch.

Claims (1)

[Claims] 1. A motor, a weighing platform that rotates in conjunction with the motor and on which an object to be weighed is placed, a display means for digitally displaying the weight of the object placed on the weighing platform, and a drive for the motor. A measuring instrument comprising means for fixing, at a predetermined value, lower digit numerical values that fluctuate among the numerical values displayed on the display means during the motor drive period in conjunction with the motor drive period.