JPS6141925A - Crystal oscillation type electronic balance - Google Patents

Abstract

PURPOSE:To improve measurement accuracy by providing electrodes, a clock generator, a counter, a controller, etc., and making the clock generator and weight sensor coincident in temperature characteristics, secular change characteristics, etc., through simple constitution. CONSTITUTION:An electrode 3 for the clock generator 6 and an electrode 2 for the weight sensor 7 are arranged on a single crystal diaphragm 1 to form oscillation circuits respectively. Further, an over-tone generating resistance 13 is connected to the oscillation circuit constituting the sensor 7 and then the oscillation circuit oscillates to generate an odd-multiple higher harmonic, e.g. three-fold higher harmonic. Namely, the generator 6 oscillates to generate a basic harmonic and the sensor 7 oscillates to generate, for example, a three-fold harmonic to increase frequency variation width when the load of a body is placed, thereby improving the sensitivity and resolution of the electronic balance. Therefore, the measurement accuracy is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a quartz crystal electronic scale using a quartz crystal oscillator as a pressure sensitive element of a weight sensor.

(Prior art) For example, Japanese Patent Publication No. 55-20175 proposes a scale as shown in FIG. When the object to be weighed is placed on the tray, compressive force due to the weight of the object is applied to the pressure sensor via the spring, pedestal, and rod, and the crystal oscillator installed in the pressure sensor is The resonant frequency changes.By detecting the amount of change in this resonant frequency, it is possible to detect the correct amount of the wave meter-!11.object.

By the way, since the stress sensitivity of such a crystal resonator depends on the ambient temperature, in an attempt to eliminate the influence of temperature, Japanese Patent Publication No. 56-18098 proposed a structure as shown in Fig. 0'14. has been done.

In this example, when a load is applied to the supply point of the crystal diaphragm where mechanical forces such as stress and strain are transmitted, electrode A has zero stress sensitivity on the crystal diaphragm, and electrode A has stress sensitivity of zero temperature dependence. Resonant frequencies are obtained from the oscillation circuit 41 ports corresponding to the mouths. The outputs of both oscillation circuits are added to a mixer, and the difference frequency of the oscillator circuit is obtained at the output terminal, thereby allowing the weight to be detected.

(Problems with the Prior Art) However, in electronic scales that input signals from one weight sensor to a controller using a microcomputer or the like to execute various calculation processes, a clock generator that drives the central processing unit (CPU) of the controller is required. Because the crystal oscillator and the crystal armature of the weight sensor were separate, it was difficult to match the temperature characteristics and peak characteristics of the two, and as a result, changes in the ambient temperature and aging caused the differences between the two. There was a problem in that the vibration frequencies became inharmonious, resulting in measurement errors. As a solution to this problem, it is possible to use a crystal mover with excellent temperature characteristics or a crystal mover with uniform characteristics, but in this case, the cost becomes very high.

Furthermore, when using a crystal oscillator with a standard vibration frequency of 10 MHz, when a predetermined stress, for example 1 kg, is applied, the frequency change range is only 0.02%, or 2 KHz degrees, so it cannot be used as an electronic balance. When used, the sensitivity and resolution are extremely poor. That is, even at full scale, only 2,000 pulses can be counted in one second of sampling, and since one pulse corresponds to 0.5 g, the resolution is extremely poor.

(Objective of the Invention) The present invention improves weighing accuracy by matching the temperature characteristics, aging characteristics, etc. of both a clock generator and a weight sensor with a simple configuration, and also improves the sensitivity and resolution of one weight sensor. The purpose is to provide a practical crystal vibration type electronic scale.

(Summary of the Invention W) The crystal biasing type electronic scale of the present invention has an electrode for a weight sensor disposed at a position where the load of an article is applied, and a clock disposed at a position where the frequency does not change due to external stress. A single crystal diaphragm that powers the electrodes for the generator, an overtone resistor connected to the oscillation circuit of the weight sensor to cause it to oscillate at odd harmonics, and a resonant frequency of the oscillation circuit. It is characterized by comprising a counter for counting, a controller to which the count value of the counter and a fundamental harmonic clock pulse oscillated by a clock generator are input, and a display section on which predetermined items calculated by the controller are displayed. It is something.

(Example) An example of the present invention will be described below with reference to the drawings. 1st
Figure (&) is a layout diagram of the crystal diaphragm of the present invention, Figure 1 (b)
is a view taken along arrow A in FIG. 1 (&).

In the figure, two electrodes are placed at different positions on the crystal diaphragm l. The electrode 2 is disposed between the upper support 4 and the lower support 5 at a position where the load W of the article placed on the upper support is applied, and is used as a weight sensor. The electrode 3 is placed at a position where the frequency does not change due to external stress, and is used as a vibrator of a clock generator.

FIG. 2 is a circuit diagram of the present invention, and FIG. i@5 is a circuit diagram of a conventional example. Conventionally, as shown in FIG. 5, separate crystal diaphragms 1 and 1' were provided as a weight sensor and a clock generator 6, and electrodes 23 were arranged on these.The resonance frequency of the weight sensor 7 was calculated based on logic. It is counted by a counter 9 through a circuit 8, and the count value is input to a controller 10 composed of a microcomputer or the like. The output from the clock generator 6 is input to the controller io through the buffer 12 as a clock pulse. The controller 10 outputs arithmetic processed signals such as a gate signal to the logic circuit 8, a clear signal to the counter 9, and a signal to the display section 11.

In the present invention, as shown in diagram m2, an electrode 3 for a clock generator 6 and an electrode 2 for a weight sensor 7 are arranged on a single crystal diaphragm l to form respective oscillation circuits.

Furthermore, an overtone generating resistor 13 is connected to the oscillation circuit constituting the weight sensor for oscillating at odd harmonics 1, for example, 3rd harmonic.

In other words, the Kuro7 Kuji generator is made to oscillate at the fundamental harmonic, and the weight sensor is made to oscillate at, for example, the 3rd harmonic, thereby increasing the range of frequency change when the load of the article is applied.
This improves the sensitivity and resolution of electronic scales.

(Effects of the Invention) As explained above, one aspect of the present invention is to arrange the electrode for the weight sensor at the position where the load of the article is applied to the single quartz rock movement plate, and clock the electrode at the position where the frequency does not change due to external stress. By arranging the electrodes for the generator, it is possible to provide temperature tracking characteristics and aging tracking characteristics for the generator and weight sensor, making it possible to improve weighing accuracy and ensure long-term stability. Accurate electronic scales are obtained. In addition, since a single crystal diaphragm is shared by the clock generator and weight sensor,
There is no need to worry about processing accuracy or element variations, etc.
The cost of the crystal diaphragm becomes cheaper.

Furthermore, since the oscillation circuit of the weight sensor is oscillated at odd harmonics, a practical electronic scale with improved sensor sensitivity and resolution can be obtained. In addition, sensitivity.

When the resolution is the same as the conventional one, the sampling time can be shortened to one-third, for example, and a practical electronic balance with good responsiveness can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a layout diagram of a crystal retractable plate of the present invention, FIG. 2 is a circuit diagram of the present invention, FIGS. 153 and 4 are layout diagrams of a conventional example, and FIG. 5 is a circuit diagram of a conventional example. 1.1'...Crystal diaphragm, 2,3...Electrode, 4...
- Upper support body, 5... Lower support body, 6... Clock generator, 7... ffE amount sensor, 8... Logic circuit, 9... Counter, 1O... Controller, 1
1...Display section, 12...Buffer, 13...Resistance for overtone. Go to Figure 3 and Figure 4 (

Claims (2)

[Claims] (1) A single crystal diaphragm that shares the weight sensor electrode located at the position where the load of the article is applied and the clock generator electrode located at the position where the frequency does not change due to external stress, weight Consisting of a counter that counts the resonant frequency of the oscillation circuit of the sensor, a controller to which the count value of the counter and clock pulses oscillated by the clock generator are input, and a display section that displays predetermined items calculated by the controller. A crystal oscillation type electronic scale featuring the following. (2) The crystal vibrating electronic scale according to claim (1), characterized in that an overtone resistor for oscillating at odd harmonics is connected to the oscillation circuit of the weight sensor.