JPS61271421A - Level detector - Google Patents

Abstract

PURPOSE:To achieve a sure detecting operation by a simple circuit structure by applying an electric pulse to an oscillator and measuring the time of a reverberation. CONSTITUTION:A microcomputer 13 comprises a CPU, a ROM and a RAM and mainly functions mainly as a detector and a pulse transmitter. When a pulse signal A transmitted from the output port of the microcomputer 13 is inputted to the base of a transistor 14, the pulse signal A is amplified and applied across the electrodes 2 and 4 of an oscillator to excite the oscillation of the oscillator. This oscillation is derived from between the electrodes 2 and 4 as a signal B, which is inputted to the base of another transistor 15 and amplified and rectified thereby. Then, the signal B is smoothed by a capacitor 16 and inputted to the input port of the microcomputer 13 as a signal C. Therefore, the pulses are applied to the oscillator at a constant interval to oscillate the oscillator and a level detecting operation is performed by picking up the reverberation of the oscillation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for sensing the level of a fluid, such as a liquid or particulate matter.

Conventionally, it has been known to use a vibrator as a level detection means and to configure it as shown in FIG.

An electrode 2 is provided on one side of the vibrator 1, and electrodes 3 and 4 are provided on the other side, and an AC voltage given from an oscillation circuit 5 is applied between the electrodes 2 and 3 to move the vibrator to 8! While mechanically causing self-excited vibration, the vibration signal is extracted between the electrodes 2 and 4, this signal is rectified via the rectifier circuit 6, and the rectified DC voltage is applied to the base wall e9f L cart in the comparator circuit 7. l 4 L
y4(?rT:m↓claw 1-) n LEA + 7
- To determine whether there is a fluid to be detected in n,
It utilizes the fact that the amplitude of the vibrator changes when it comes into contact with the object to be detected.

However, with this method, the amplitude of the diaphragm of the oscillator varies slightly due to temperature fluctuations and individual differences in the oscillators, causing the detection voltage to fluctuate, which not only risks detection errors, but also causes the oscillator to be affected by the reference voltage. A means for adjusting the reference voltage or the detection voltage is required so that the detection voltage is at a level between the detection voltage when in contact with the sensing object and the detection voltage when not in contact, which makes the circuit complicated and expensive. In addition, since the vibrator is always vibrated during the detection operation, there is a problem in that the vibration generates noise.3 This invention addresses the above problems and provides a device that obtains reliable detection operation with a simple circuit configuration. , -.

Specific examples thereof will be explained below based on FIGS. 2 to 4.

FIG. 2 shows an example of the basic configuration of the present invention. Reference numeral 10 denotes a pulse transmitter that transmits pulses of a constant level at predetermined intervals and applies them to the electrodes 2 and 3 of the vibrator 1 having the same configuration as in FIG. 11 is a rectifier circuit, in which a vibrator 1 is generated by an electric pulse applied from a pulse generator 10;
A vibration signal is obtained between electrodes 2 and 4, and this is amplified, rectified,
It is smoothed etc. Reference numeral 12 denotes a detection unit that time-counts and obtains the wavelength of the vibration signal from the rectifier circuit 11, and detects whether or not the diaphragm of the vibrator 1 is in contact with the object to be detected according to this wavelength.

FIG. 3 shows an example of a circuit according to the present invention, and FIG. 4 shows signal waveforms of each part of the circuit. A microcomputer 13 includes a CPU, a ROM, and a RAM, and mainly functions as the detection 812 and pulse generation 310 based on a program registered in the ROM.

When the pulse signal A transmitted from the output capacitor (a) of this microcombiner 13 is output to the base of the transistor 14, it is amplified and applied to the electrodes 2 and 3 of the vibrator 1, to excite vibrations. The vibrations generated in this way are collected as a signal B between the electrodes 2 and 4, and are input to each of the transistors 15 to be amplified and rectified.
The signal C is smoothed by a capacitor 16 and sent to the human-powered boat B of the microcomputer 13.

Therefore, a pulse is applied to the vibrator 1 at a certain interval to cause it to vibrate, and the reverberant vibration is collected to perform a level detection operation.
Part 7 of the main program of the microcomputer shown in the figure
The explanation will be based on the 0-chart.

When the signal C is input to the input port (1), a time count is performed based on the tarock signal from the tarock transmitter built in the microcomputer 13 (2), and the signal C is
Find the wavelength t. Next, the obtained value is the reference wavelength t.

Compare with (4) If the wavelength is longer than shi, t, set "0" in the register Y that provides detection data (5), set that the level of the detected object is lower than the detection level, and If the wavelength is shorter, set "1" in register R (6), set that the level of the detected object is higher than the detection level, and return.

The present invention is configured as described above, and by applying an electric pulse to the vibrator, measuring the time of the reverberant vibration, and detecting the presence or absence of a contact relationship between the vibrator and the object to be detected, it is possible to Rather than detecting the amplitude of the vibrator as in the conventional method, it detects the dead time of the vibration of the vibrator. There is no fear. In other words, the reverberation time of the transducer differs by several times when it is in contact with the object to be detected and when it is not in contact, and is so clear that the slight effects of temperature differences and individual differences can be completely ignored. It is possible to make a clear judgment. Further, in the present invention, there is no need to constantly vibrate the vibrator during the detection operation as in the conventional case, and generation of harsh noise caused by vibration can be suppressed to an extremely low level.

[Brief explanation of drawings]

fjS1 Figure is an explanatory diagram showing the configuration of a conventional example. Figure 2 is an explanatory diagram showing the basic configuration of an embodiment. Figure 3 is an electric circuit diagram of the embodiment. Figure 4 is a diagram of main signal waveforms of the embodiment. Fig. 3 showing the detection operation of the embodiment Fig. 4 Fig. 5

Claims (1)

[Claims] A level detection device characterized by applying an electric pulse to a vibrator and measuring the time of its reverberant vibration to detect whether there is a contact relationship between the vibrator and an object to be detected.