JPH02161321A - Liquid level detector - Google Patents

Abstract

PURPOSE:To prevent a detecting element including a temperature sensing element from being corroded with the liquid of an object to be detected, etc., and also, to simplify a structure by attaching the temperature sensing element for outputting a temperature sensing signal corresponding to its own temperature to the outside surface of a side wall of a container including a liquid in the inside and detecting the liquid level of the liquid, based on the temperature sending signal. CONSTITUTION:On the outside surface of a side wall 1a of a container 1 in which a liquid 2 is housed, a temperature sensing element 3 for outputting a temperature sensing signal 3a corresponding to its own temperature to a circuit part 5 is stuck by a heat conductivity type adhesive 4. In the case when the inside surface opposed to a temperature sensing element 3 fitting part of the container side wall 1a is brought into contact with the liquid 2, and in the case when the inside surface is brought into contact with the gas of the upper part of the liquid 2, diffusion coefficients of heat diffused to the inside of the container 1 from the temperature sensing element 3 heated by a heating means 18 are difference from each other, therefore, in accordance with the liquid level of the liquid 2 in the container 1, the temperature of the temperature sensing element 3 is varied. Accordingly, by the temperature sensing signal 3a from the temperature sensing element 3, the liquid level can be detected. In this case, since the temperature sensing element 3 is attached to the outside surface of the container and is not brought into contact with the liquid 2 and gas thereon, it is scarcely corroded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention detects the liquid level by utilizing the temperature change of a temperature sensitive body based on the difference between heat dissipation in the gas phase and heat dissipation in the liquid phase. The present invention relates to a liquid level detection device in which a temperature sensitive body is less likely to be corroded by a liquid to be detected and a gas above the liquid and the structure of a temperature sensitive body mounting portion can be simplified.

[Conventional technology]

Conventionally, a liquid level detection device using a directly heated type or indirectly heated type thermistor having negative resistance has been known ("Level meter" edited by the Japan Measuring Instruments Association).

pp. 202-205, published by Corona Publishing). Yes L
In this device, when the thermistor is in a liquid, the heat dissipation constant K of the thermistor is large, and when the thermistor is in a gas, the constant K is small, and as a result, the current flow of the thermistor is The relationship between and the voltage V is as shown in Figure 8. Therefore, if the current is set to a constant value, the voltage V will be different when the thermistor is in a liquid and when the thermistor is in a gas. Based on this change in voltage V, one liquid level is detected.

[Problem to be solved by the invention]

The liquid level detection device R using the above-mentioned thermistor uses a thermistor with high temperature detection sensitivity in the detection section, so it has the advantage of high liquid level detection sensitivity. However, in this case, since the detection section comes into contact with the liquid to be detected or the gas above the liquid, there is a risk that the components of the detection section may be corroded, and the reliability of the liquid level detection device is low. There is a point. In addition, in this liquid level detection device, the detection section must be inserted into a container containing the liquid, so the structure of the container opening for inserting and removing the detection section must be appropriately designed, and the container and detection section must be properly designed. If the container and container are sealed, it is necessary to have an appropriate electrical insulation structure between the container and the detection section, which makes the structure of the container and detection section complicated. There are also points.

An object of the present invention is to eliminate the need to push a detection section using a temperature sensitive body such as a thermistor into a container, thereby reducing the risk of corrosion of the detection section. Another advantage is that the structure of the detection unit and container can be simplified.

[Means to solve the problem]

According to one aspect of the present invention, the above problems are solved.

A temperature sensing element attached to the outer surface of the fl wall of a container containing a liquid and outputting a temperature sensing signal according to its own temperature, and a heating means for heating the temperature sensing element, A liquid level detection device is configured to detect a liquid level of the liquid in the container.

[Effect]

With the above structure, the inner surface of the side wall of the container facing the temperature sensitive element mounting part is heated by the heating means when it is in contact with the liquid button and when it is in contact with the gas above the liquid. Since the dissipation coefficient of heat radiated from the thermosensor into the container is different, the temperature of one thermosensor will change depending on the liquid level in the container.The liquid level should be detected from the temperature sensing signal. Can be done. In this case, the temperature sensitive body is attached to the outside of the container and does not come into contact with the liquid or the gas above it, so there is less fear that the temperature sensitive body will corrode.
In addition, the structures of the temperature sensing body and the container can be made simpler than in the case of a conventional liquid level detection device in which the temperature sensing body is inserted into a container.

〔Example〕

FIG. 1 is an explanatory diagram of the configuration of an embodiment of the present invention, and FIGS. 2 and 3 are enlarged configuration diagrams of the main parts of the upper opening 1, each of which has a different adhesiveness from the ggt diagram. In FIGS. 1 to 3, a container 3 containing a 'c and ttz liquid 2 is attached to the outer surface of the side wall 1a of the container with a thermally conductive adhesive 4, and is a temperature-sensitive container that corresponds to its own temperature. A temperature sensing element outputs a signal 3a, and 5 is a circuit section that performs an operation described later when the temperature sensing signal 3a is input, and outputs a detection signal 5a according to the result. That's it 1. In this case, the temperature sensor 3 includes a rectangular substrate 6 made of an electrically insulating material, and a thin film made of a material such as nickel or nickel-O-chromium alloy in a shape of 99 folds formed on one surface of the substrate 6 by vapor deposition or the like. It is composed of a resistor 7 which is a shaped badan, terminals 7a*7b formed at each end of the resistor 7, and an electrically insulating coating 11jJ8 applied to insulate adjacent resistors. The temperature sensing signal 3a is input to the circuit section 5 via the conductor IIJ99 connecting the terminals 7a, 7b and the circuit section 5.

Next, the configuration and operation of the circuit section 5 are shown in FIG. 1 is an oscillator! A current flows through the input of the temperature sensing element 3, and the voltage between the terminals 7ae and 7b, which is the temperature sensing signal 3 outputted by the temperature sensing element 3, corresponds to the voltage 8:E1. 12 is an integrator C, -R, which receives the output signal of the buffer amplifier 11 and outputs the voltage signal E0. Reference numeral 13 denotes a temperature-compensating temperature-sensor having the same structure as the temperature-sensor 3 and attached to the side wall 1a of the container; 14, a predetermined constant current is applied to the temperature-sensor 13 by means not shown; This is a buffer amplifier that amplifies the voltage generated across the waist temperature sensor as a result of the current flow and inputs the output type EEBS to the comparator 15. In this case, the comparator 15 receives the voltage EEF3 output from the integrator 12. ．． Furthermore, when Bo exceeds Ha, the comparator 15 outputs the aforementioned detection signal 5.
It is configured to output a. Thus, the circuit section 5 described above consists of the various sections shown in FIG. 4 except for the temperature sensing element 3.

The circuit section 5 is constructed as described above.

When a voltage V is applied to the series circuit consisting of the temperature sensor 3 and the resistor R1 from the oscillator 10, a current flows through the resistor 7, and the resistance value R of the resistor increases due to self-heating. Increased 1. The voltage E between the terminals 7a and 7b is a pulse train button in which the peak value increases with time in a first-order lag manner as shown in FIG. Yes C.

At this time, the temperature sensor 3 is attached to the fl-c color container side wall I11.
(opposing side) 3111m inner surface portion 131
When the resistor 7 pl is in contact with the liquid 2 and heated by the electric current EE Vt K, the heat passes through the side wall 1a and becomes ``cwL''.
Since heat is transmitted to the body with a large heat dissipation constant Kt, the peak value of each pulse in the pulse train 'tl FE E I increases in a first-order lag manner with a short time constant TI.
Eventually, the voltage drops to a low equilibrium voltage Vbs corresponding to the low equilibrium temperature θ of the resistor 7, resulting in a clear pulse train A, but al
The inner surface portion Sat of the wall la is the gas 16KIi above the liquid 2 in the container IK! When the resistor 7 is heated by the voltage V, heat propagates through the side wall 11 into the gas 16 with a small heat dissipation constant Ks. The peak value of each pulse is TI
With a time constant T, which is longer than , the pulse train increases in a first-order lag manner and finally settles at an equilibrium temperature Vbz that is higher than Vbt corresponding to the equilibrium temperature θ, which is higher than the θ temperature of the resistor 7. . 1. When the voltage EEB to the pulse train B is input to the integrator 12, the waveform of the output voltage E at this time becomes the smoothed waveform shown by C in FIG.
)-E is input to the integrator 12, the integrator 12 outputs N aE Fit exhibiting the smoothed waveform shown in FIG. If the settings are set as shown in FIG. 5, the detection signal 5a will be output from the time comparator 15 of waveform C.
2, but when the waveform is correct, the detection signal 5a is output from the comparator 15 at time t0.

That is, in the liquid level detection device 17 which is made up of the various parts shown in FIG. 1 except for the container 11, C is the inner surface portion t of the container side wall 1a.
When the state in which at is immersed in the liquid 2 changes to the state in which the inner surface portion tat is exposed above the liquid 2, the detection signal 5a is output from the circuit section 5.

By outputting the signal 5a, the level of the liquid 2 can be detected. Then, in the liquid level detecting device 17, the circuit section 5 is placed near the temperature sensing element 3, and the resistance values of the temperature sensing element 3 when not heated by the C, C temperature sensing 13 and the oscillator 10 are determined. Since it is necessary to change the liquid level by the same value with respect to the ambient temperature, the above-mentioned liquid level detection by the detection device 17 is not affected by the ambient temperature change (this means that it is done correctly). In the button and the detection device 17, the resistance value ratio of the resistor 7 to the temperature sensor 3 changes t according to the temperature of the resistor 1.As a result, the voltage E corresponding to the resistance value RK changes t. This electric IEBI takes the temperature sensing signal 3a to the circuit section 5, and inputs the following.

Therefore, in the case of the liquid level detection device 17, it can be said that the temperature sensor 3 outputs the temperature sensing signal 3a according to its own temperature and the pulsed voltage B. [
Since each part in 17 is busy as described above, the generator 10 and the fixed resistor R8 constitute a heating means (8) for heating the temperature sensing element 3 to 10.degree. That's it 1. Furthermore, it can be said that the detection device fl17 detects the level of the liquid 2 in the container 1 based on the temperature sensing signal 3a and the appropriate voltage Fl.

The configuration and operation of the liquid level detection device 17 are as described above, and the temperature sensing element 3 is a container! It is installed outside the building.

In this case, the temperature sensitive body 3 does not come into contact with the liquid 2 or the gas 16 above it, so there is no fear that the temperature sensitive body 3 will be corroded by these liquids or gases.

In addition, in this case, there is no need to insert and fix the temperature sensing element 3 into the container l, so the structure of the temperature sensing element 3 and the container l can be changed more easily than in conventional liquid level detection devices. Be able to do it.

FIG. 6 shows Wg2 embodiment 19 of the present invention! In the II-formation explanatory drawing, there is a thermally conductive material on the side of the temperature sensing element 3 and the protective film 8 of this temperature sensing element, as shown in the enlarged cross-sectional views in the hx and faXT figures. The temperature sensing body 22 is made up of a silicone rubber 20 with good thermal conductivity pasted with adhesive and a knob portion 21 pasted with adhesive on the back side 1ii1 of the substrate 6 of the temperature sensing body 3.
Corresponds to the thermosensor 3 shown in Figure 1.
'I'c, in this case the temperature sensing element 22 is connected to the knob part 2.
By pinching 1 by hand or holding it with a holder (not shown), 1 silicone rubber 20 is removably pressed onto the outer surface of the container side wall 1a. If the C1 liquid level detection device is configured as shown in FIG. 6, the mounting position l of the temperature sensing element 22 can be easily changed.

Furthermore, by sliding the temperature sensing element 22 on the outer surface of the container side g 1 m in a continuous manner, the liquid level at that point can be measured.

In each of the above-mentioned embodiments, C is such that the temperature sensing element 3 is a resistor 7 made of nickel-chromium alloy or the like, but 1
In the present invention, it is also possible to use the temperature sensing element 3 as a thermostatic sensor, in which case the circuit section 5 will be configured in accordance with this thermistor.

〔Effect of the invention〕

As described above, 1 & The liquid level detection device was configured to detect the liquid level in the container based on the temperature sensing signal.

Therefore, with the above configuration, the inner surface of the side wall of the container facing the temperature-sensing element attachment part is in contact with the liquid (L'''L) and in the case where it is in contact with the gas above the liquid, the heating means This is because the dissipation coefficient of heat dissipated from the heated temperature sensitive element into the container is different.

Since the temperature of the temperature sensing element changes depending on the level of the liquid in the container, the liquid level can be detected from the temperature sensing signal. In this case, the temperature sensitive body is attached to the outer surface of the container and there is no need to prevent the liquid or the gas above from leaking, so the present invention reduces the risk of corrosion of the temperature sensitive body. In addition, the structure of the temperature sensitive body and the container can be made simpler than that of a conventional liquid level detection device in which the temperature sensitive body is inserted into a container.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the configuration of the first embodiment of the present invention, Fig. 2 is a cross-sectional view of the main part in Fig. 1, and Fig. 3 is a plan view of the thermosensor 3 soaked with water shown in Fig. 1. , FIG. 4 is a configuration diagram of the circuit section 5 shown in FIG. 1, FIG. 5 is an explanatory diagram of waveforms of the main parts in FIG.
7 is a sectional view of the temperature sensing element 22 shown in FIG. 6, and FIG. 8 is a detailed explanatory view of the present invention. 1... Container, la... Side wall, 2...
...Liquid, 3.22...Thermosensitive body, sa*B,...
... Temperature sensing signal, 17.19 ... Liquid level detection device. 18... Heating means. Notebook Atsushi Bookmark Booklet Notebook Electric Press I [m4] Notebook δ Diagram

Claims (1)

[Claims] 1) A temperature sensing element attached to the outer surface of a side wall of a container containing a liquid and outputting a temperature sensing signal according to its own temperature, and a heating means for heating the temperature sensing element, the temperature sensing element generating a temperature based on the temperature sensing signal. A liquid level detection device that detects the level of the liquid in the container.