JPS59108921A - Liquid level detecting device - Google Patents

Abstract

PURPOSE:To avoid erroneous detection at the time of abnormality such as load fluctuation and to improve reliability, by detecting the decrease in the liquid level of a device whose liquid level is to be controlled, thereafter stopping the device once, restarting the device after a specified time, and continuously stopping the device based on the detection of the decrease in the liquid level again. CONSTITUTION:When a liquid level detecting element 6 emerges from liquid to air, pulses are inputted to an input part 18a of a counter circuit 18, and a signal is outputted from an output part 18c after the counting of a specified times. A timer circuit 22 is started, and a stopping signal is outputted from an output circuit 14. When the time of the timer circuit 22 is up, the H signal outputted from a timer output part 22b temporarily turns ON a transistor 23. A counter circuit resetting part 18b is made to be an L level, and the counter circuit 18 is reset. Thus the counting is made possible again. The counter circuit output part 18c becomes the L level, the output circuit 14 is turned ON, and the operating state is obtained again. The operation is once stopped and restarted again. Therefore, even though the liquid level is temporarily decreased and the erroneous operation is performed, the normal operation is resumed again.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention provides liquid level control for devices that require all liquid level management. Liquid level detection element such as a positive resistance characteristic temperature element or a negative resistance characteristic temperature element? This invention relates to an improvement of a liquid level detection device used for detection.

Conventional thermistor element used as liquid level detection element 'A J
Due to the difference in the heat dissipation coefficient of the thermistor element due to the O difference, internal resistance rapidly decreases due to self-heating in air?
Is it considered as a device that can be used to detect the entire liquid level?
Shown in Figure 1.

In Figure 1, (1) is a transformer, +21 is a rectifier circuit, 13J f/ff smoothing capacitor, +41 is a stabilizing power supply circuit, (511f is a current limiting resistor to the surface detection element (thermistor element in this example), +61 1 is a liquid level detection element composed of a thermistor element, (7) is a high impedance FET input arithmetic amplifier circuit, and a relatively large capacity capacitor (8) is an analog memory for holding the voltage for the entire period. together with the peak detection circuit (9
) all configured. a2 is a voltage dividing circuit with a resistance of +101,
Qll determines the output voltage of the peak detection circuit (9)? The partial pressure is divided to a predetermined value. 03 is a comparator that completely compares the peak detection circuit (output wheel of 91, pressure (potential at point b) and direct detection signal voltage (potential at point a) from the liquid level detection element (potential at point a) divided at the voltage dividing circuit port, It is usually configured using a high input impedance operational amplifier.05 is an inverting circuit that inverts the output sound of the comparator (]3, and OG is a differentiating circuit that converts all outputs of the inverting circuit (19) into pulses and converts the output sound of the counting circuit Q81. When the input is input to the input section (18a) and counted a predetermined number of times, it is outputted from the output section (18b) to the self-holding circuit 4, and the signal is fed to the output circuit 04). Controls the start and stop of alarms or controlled equipment.

In the conventional device formed in this way, when the potential at point a and the potential at point b are fully compared, that is, when the liquid level detecting element (6) comes out from the liquid into the air, self-heating occurs in the liquid level detecting element (6). The resistance suddenly decreases, and the potential at point a decreases rapidly, but b
Is the potential at the point the peak voltage when the liquid level detection element (6) is submerged in the liquid? Therefore, even if the potential at point A suddenly decreases, the entire operation is very slow, and the comparator
The potentials of point and point b are all compared and output, and the signal is converted into a full pulse, and the liquid level is detected after counting a predetermined number of times.Is this a problem? had.

This is because when the liquid level of the controlled device temporarily drops due to load fluctuations, etc. even though it is not in an abnormal state, if the set number of counts is small, the predetermined number of times may be counted, causing a malfunction. invited. Also, in order to prevent malfunctions, there were times when the number of counts was set to be higher than the actual value, but due to the true drop in the liquid level, an external alarm or a controlled device was issued? Equipment that does not work or is slow to work when it should be stopped? This may cause damage, so determining the number of counts depends on the purpose of the controlled equipment,
t) It is necessary to change depending on the conditions and the type of target liquid medium.
Knowledge of the equipment and effort required to repeatedly change settings. Moreover, when detecting the internal front surface of a refrigerant compressor used in a refrigeration system, the conditions often fluctuate from moment to moment depending on the load conditions, making it difficult to set the optimum number of counts. It was unreliable.

In this invention, after detecting a drop in the liquid level of the liquid level management device, all of the above devices are stopped, restarted after a predetermined period of time, and continued to stop when a drop in the liquid level is detected again. A liquid level detection device that does not cause errors? There is something to offer.

An embodiment of the present invention will be explained below with reference to the drawings. Second
In the figure, are the same symbols as in Figure 1 the same or equivalent parts?
show. In the figure, the output section of the counting circuit (to) is connected to the timer circuit @, and the inverting circuit c! n'2, and is controlled to relay cA' of output circuit a4. The output section (22b) of the timer circuit (2) is connected to the self-holding circuit (1).
1' to the oscillation control section (22c) of the timer circuit @, and after the timer circuit (A) times up, the timer circuit (A) does not function until any reset operation is performed. The output part (22b) of the Mayu timer circuit ■ is a differential circuit (
2) is connected to the reset section (18b) of the counting circuit, and after time-up, the pulse is added to the reset section (18b) and reset to the counting circuit (g), making it possible to count again. With this configuration, a pulse is input to the input section (tSa) of the counting circuit (to) and the word 1 is input.
The counting part is the same as the conventional one shown in Fig. 1, but after counting a predetermined number of times, the output section (18c) outputs a ``GH'' level signal, starts the timer circuit (a), and starts timer measurement. At the same time, the inverting circuit 1) becomes a ``LOW'' level signal because it goes through all the ')
1) No excitation occurs. When the timer circuit (2) times up, the ``old G'' output from the timer output section ('22b)
f("The level signal is generated by the self-holding circuit a (19a)
Initial setting operation from outside? Since the ``LOW'' level signal continues to be supplied to the timer circuit oscillation control section (22c), the timer circuit (2) never functions.

Also, at the 1st hour, h-1ζ is output from the timer output section (22b).
On the way, the output passes through the differential circuit (c) and is turned into a signal.Then, the transistor (2) 71 is temporarily turned on and the counting circuit is turned on. The counting circuit is reset to On, and becomes ready to count again. At the same time, the counting circuit output IB (18c) goes to the 'LOW' level, and the output circuit is driven by the signal set to the 4 old GH' level at the inverting port w!rI2B. It becomes ON state and becomes operational state again.

If all these time charts are shown, it will be as shown in Fig. 4.

Therefore, in a circuit configured in this way, since the unit sum operation is stopped and then restarted, even if the liquid level temporarily drops and there is a malfunction, as in the conventional case, the circuit will recover again, which will completely hinder operation. Therefore, malfunctions can be reliably prevented. In this case, it is also possible to output only the alarm signal continuously even after restarting.

In the embodiment shown in FIG. 3, the self-holding circuit (A)? After that, the timer circuit (A) starts at the same time, and if the counting is completed before the timer goes up, the counting circuit resets the reset section (18b) after the timer stops until the timer goes up). It will start operating again, but will continue to stop if it detects the full liquid level again and stops again. That is, at the same time as the input signal is input to the input section (18a) of the counting circuit 0, the timer circuit (A) is simultaneously started by the self-holding circuit (A) and maintained in the timer operating state. If the predetermined count is not reached by the time the time-up is completed, the timer circuit @ is automatically reset by the circuit 4. When the predetermined number of counts is reached before the time-up is completed, a stop signal is issued during the period from the completion of the predetermined count to the completion of the timer-up as described above, and the signal is held by the self-holding circuit Q and is sent to the output circuit 04) to continue the stop signal. do. When the time-up is completed, the timer circuit output section (22b
), a “HIGH” level is output and the differentiation circuit (c)
Transistor (c) through? Is the counting circuit reset section (g) temporarily turned on? ``'LOW'' level counting circuit σal? At the same time as resetting, a 'HIGH' level pulse is sent through the entire differentiating circuit (a) and the output section on the counting circuit side (
18c) LOW- level is self-holding circuit CIIK
The signal is output and the output circuit side becomes operational. However, since the timer circuit (a) remains in the time-up state, when the counting circuit (a) counts the predetermined number of times again, the output circuit α stops. Since the timer circuit (sub) does not function, it will not automatically return to the operating state again, and unless an external input is input to the reset circuit aη, the output circuit a4 will remain in the stopped state. If all these time charts are shown, it will be as shown in FIG.

The circuit configured in this manner not only restarts after a certain period of time as shown in the embodiment in FIG. In the case of detection due to a drop in the liquid level, the automatic nJ is adjusted so that it stops for a long time, and in the case of detection due to a slow drop in the liquid level, it stops for a short time. Due to automatic adjustment in this way, if the liquid level drops quickly, the controlled equipment is stopped for a long time and then restarted, so the liquid level can be recovered, and if the liquid level drops slowly, it will not cause much trouble, so it will be shortened. This method has great effects in automatic control equipment because it avoids the problems that occur when all controlled equipment is stopped for a long time because it can be restarted in a timely manner.

As described above, according to the present invention, the device is temporarily stopped by the liquid level detection signal of the liquid level management device, restarted, and continuously stopped by the liquid level detection signal again, so that load fluctuations, etc. There are various effects such as no false detection in the event of an abnormality and improved reliability.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a conventional liquid level detection device, Fig. 2 is a circuit diagram showing an embodiment of the present invention, Fig. 3 is a circuit diagram showing another embodiment of the invention, and Fig. 4 is a circuit diagram of a conventional liquid level detection device. Are the figures and figures 5 the operations of figures 2 and 3? FIG. In the figure, (6) is the liquid level detection element, (9) is the peak detection circuit, 03 is the comparison circuit, circle is the output circuit, α119 (C) (to) is the differentiation circuit, (G) is the counting circuit, (I) ) is a timer circuit and a self-holding circuit for OI. In addition, the same reference numerals in the drawings indicate all the same or corresponding parts. Agent Makoto Kuzuno

Claims (2)

[Claims] (1) A liquid level detection element that is disposed at a liquid level detection position of a device that requires liquid level management and generates a voltage signal according to the liquid level;
What is the peak value of the voltage signal output of this liquid level detection element? A peak detection device that detects and holds it for a predetermined time, a voltage dividing circuit that divides the total voltage signal detected by the peak detection device, and a voltage signal from the divided voltage and the liquid level detection element? Compare and output signal according to comparison value? When the comparator generates and the number of noises output by this comparator reaches a predetermined value, a liquid level detection signal sound is generated, and the device is stopped for a while and restarted after a predetermined time to check the liquid level again. Is there a way to continuously stop using a detection signal? A liquid level detection device with all the following features. (2) Equipment 7 - How long does it take to restart after the equipment is stopped?
Claim 1 is characterized in that the output of the comparator corresponds to the time it takes to count all 4g outputs and reach a predetermined value.
The liquid level detection device described in .