JPS5824736B2 - liquid level detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid level detection device that can detect level changes in a liquid to be measured in stages.

Conventionally, this type of device detects the liquid level of a liquid to be measured in stages using a float containing a magnet and a plurality of reed switches that are opened and closed by the magnet.

However, this conventional detection method requires a magnet that has the magnetic force necessary to open and close the reed switch, and also requires a float that provides buoyancy to float this magnet.

In particular, this detection method has the disadvantage that it is nearly impossible to reduce the size and weight of the device because it utilizes the magnetic attraction between the reed switch and the magnet.

The present invention solves the above-mentioned drawbacks by providing a plurality of ring oscillation circuits including a float that responds to changes in the liquid level of the liquid to be measured and a coil as one component, and moving the coil to each predetermined liquid level detection position. The oscillation state of the ring oscillation circuit is changed depending on the presence or absence of magnetic coupling between the coil and the conductive annular body arranged on the float, and the total current consumption change of the plurality of ring oscillation circuits is changed. It is an object of the present invention to provide a liquid level detection device that can detect changes in the liquid level of a liquid to be measured in stages and that can be made smaller and lighter.

An embodiment of the present invention shown in the drawings will be described below.

FIG. 1 is an electrical wiring diagram of a liquid level detection device according to the present invention.

In FIG. 1, 100 is a detection circuit section that outputs the position of the float 180 that moves in response to changes in the liquid to be measured as a voltage change, and 150 is a display circuit section that detects and displays the position of the float 180.

In the detection circuit section 100, 110 is a ring oscillation circuit consisting of three inverters 111, 112 and 113 and a coil 114, and 120 and 130 are ring oscillation circuits having the same configuration as the ring oscillation circuit 110, Resistors 141 and 142 of different values are connected to the power supplies of the ring oscillation circuits 120 and 130, respectively.

and the power input side of the ring oscillation circuit 110 and the resistor 1.
One end of 41 and 142 is a resistor 151 of the display circuit section 150.
It is connected to the positive side terminal of the power supply 110 via.

In the display circuit 150, 152, 153, 15
4 and 155 are resistors that create the reference voltage, 156, 157 and 1
58 is a comparison circuit that compares the voltage output from the detection circuit section 100 with the reference voltage generated by the resistors 152, 153, 154, and 155; 159, 160, and 161 are resistors;
2,163 and 166 are driving transistors, 167.1
68 and 169 are lamps that display the liquid level.

FIG. 2 is a partial cross-sectional structural view of the part of this device used for liquid level detection.
The float 180 moves in the direction of the arrow in response to fluctuations in the liquid level.

The ring oscillation circuit 110 is installed inside this support 820a.
, 120 and 130, respectively.
and 134 are provided, and these coils 114°12
Terminals 4 and 134 are led to an electric circuit section 21 built in the housing 20 and connected to constitute the ring oscillation circuits 110, 120, and 130 of FIG. 1, respectively.

In addition, the float 180 is connected to the support column 20a by the stopper 20b.
It has a structure that does not come off easily.

Next, FIG. 3 shows the structure of the float.

In FIG. 3, a float 180 is made of a float base material 31 made of a non-conductive material, and an annular body 32 made of a conductive material is disposed on the inner periphery thereof.

Next, the operation of the above configuration will be explained.

First, as shown in FIG. 2, the liquid level L1 of the liquid 10 to be measured is
In this state, the float 180, particularly the conductive annular body 32, does not cover the three coils 114, 124, 134 that are one component of each ring oscillator circuit 110, 120, 130.

Therefore, self-induced electromotive force is generated in the coil.

Therefore, the ring oscillation circuit including the coil shown in FIG. 4A connects the input of the inverter gate 401 and the output of the inverter gate 403 via the delay circuit 410, as shown in FIG. 4C, due to the self-induction effect of the coil.

It becomes equivalent to a continuous circuit, and the oscillation frequency f1 at this time is f
, =x/(3τ+t) (where τ is the delay time of the signal propagation speed of one inverter gate, and t is the delay time due to the self-induction effect of the coil).

The inverter gate used in this example was manufactured by U.S. RCA (
The oscillation frequency f of the oscillation circuit is approximately 300 KHz (hereinafter referred to as low oscillation).

Next, when the liquid level of the liquid to be measured 10 is at level L2, the float 180 covers only the coil 134, and therefore is in a magnetically coupled state with the conductive annular body 32, and a self-induced electromotive force is generated in the coil 134. The ring oscillation circuit including the coil 404 shown in FIG. 4A is connected to the input of the inverter gate 401 and the inverter gate 1 as shown in FIG. 4B.
This is equivalent to a normal ring oscillation circuit in which the output of 403 is short-circuited, and the oscillation frequency f2 at this time is f2ζ1/3τ.

The oscillation frequency f2 in this embodiment is approximately 6.000 IG (z (hereinafter referred to as high oscillation)).

Since the coils 114 and 124 of the other ring oscillation circuits 110 and 120 are not covered by the float 180, they oscillate at approximately 300 KHz as described above.

Then, when the liquid level reaches level L8, the float 180 covers only the coil 124, so the ring oscillation circuit 120 performs high oscillation and the other ring oscillation circuits 110 and 130 perform low oscillation by the same operation as described above, and the liquid level decreases. It is clear that when level L4 is reached, only the ring oscillation circuit 110 performs high oscillation, and the other ring oscillation circuits 120 and 130 perform low oscillation.

Here, it is well known that the relationship between current consumption and input frequency of C087MO8IC has the characteristics shown in Figure 5, and the current consumption of a ring oscillation circuit whose oscillation frequency changes greatly as in this example also changes greatly. It is clear that in this embodiment, the ratio of the current consumption f, f2 of the ring oscillation circuit when the float 180 covers the coil and when it does not cover the coil is f: f2'; 10:1.

This means that if the impedance of the ring oscillation circuit seen from the power source when the float covers the coil is (Z)Ω, then the impedance of the oscillation circuit when the float does not cover the coil is (IOZ, lΩ). means.

As a result of the above, when the liquid level is at Ll, the detection circuit section 100 of FIG. 1 is a circuit in which the impedance of each ring oscillation circuit 110, 120, and 130 is set to (IOZ)Ω as shown in FIG. 6A. It is written in .

The voltage of the line 101 at this time is assumed to be 1.

When the liquid level is at L2, the float 180 is connected to the coil 13 of the ring oscillation circuit 130 as described above.
Since only 4 is covered, the impedance of this ring oscillation circuit is (Z)Ω, and the voltage 2 at point 101 at this time, represented by the circuit shown in FIG. 6B, is the voltage 2 above.

The liquid level becomes lower (calculation formula is omitted) and R
3, only the ring oscillation circuit 120 becomes [Z]Ω.

Here, the resistance values of the resistors 141 and 142 connected to the power supplies of the ring oscillation circuits 120 and 130 are set to [R1]Ω and [R
2]Ω, and if this magnitude relationship is R1<R2, the voltage V3 of the line 101 at this time will be lower than the potential (2).

Therefore, it is also clear that the voltage v4 of the line 101 when the liquid level is at R4 is even lower than the voltage (3).

That is, a voltage signal corresponding to a change in the level of the liquid 10 to be measured appears on the line 101 in FIG.

This voltage signal is applied to the comparison circuit 1 of the display circuit section 150 in FIG.
56, 157 and 158 on the inverting input side.

Resistors 152 and 153 are provided on the non-inverting input sides of the comparison circuits 156, 157 and 158 to detect the voltage signal.

The signals of the reference voltage ■1°■ and v3 produced by 154 and 155 arrive.

These reference voltages ■1, ■2 and ■3 and the liquid level L
1 pL2 pL , the voltages v1 , v2 . generated on line 101 in response to changes in L . v3 and ■4
The relationship is Vl>vl>v2>v2>V3>V3>v
, said Natte.

Therefore, when the level of the liquid 10 is at Ll, the voltage on the line 101 is 1 as described above, so the outputs of all the comparator circuits 156, 157, and 158 are "O".
A signal is generated, transistors 162, 163, and 166 are all cut off, and indicator lamps 167, 168, and 169 are turned off.

Then, when the level of liquid 10 reaches R2, ° line 1
Since the voltage of 01 becomes v2, only the output of the comparator circuit 156 becomes a '1'' signal, which makes the transistor 62 conductive and the indicator lamp 167 lights up.

Furthermore, when the level of the liquid 10 reaches R3, the comparison circuit 15
The outputs of 6 and 157 become 1'' signals, and indicator lamps 161 and 168 light up.When the level of liquid 10 reaches 24, all indicator lamps 167, 168, and 169 light up.

In this way, the liquid level of the liquid to be measured 10 can be detected in stages.

In addition, Figure 5 is the 1975 version of rROA C087MO.
8IC5election Guide/Data/A
Application Notes J shows that as the oscillation frequency f becomes higher, the power consumption P increases significantly, and each data is obtained when the power supply voltage VDD and the capacitor load Co are changed.

Furthermore, although the ring oscillation circuit in this embodiment is composed of three inverter gates, an odd number is sufficient, and the IC used is not limited to the C087MO8IC (the current consumption It is fine as long as it depends.

Furthermore, in this embodiment, the level detection of the liquid to be measured 10 is performed in three ways.
Although the detection is performed in stages, it is also possible to perform multi-stage detection by adding a ring oscillation circuit including a coil.

Further, although the above-described float 180 has the conductive annular body 32 disposed on its inner circumference, it may be placed on the outer circumference or the outer surface of the float 180, and the coil 114 may simply respond to the float 180. , 124° and 134, it is possible as long as it provides a magnetic coupling relationship.

As described above, the device of the present invention includes a float that responds to changes in the liquid level of the liquid to be measured, and a plurality of rings each having a coil as one component and each of the coils being arranged at a predetermined liquid level detection level. an oscillation circuit; a conductive annular body disposed on the float and magnetically coupled to the force of each of the coils to change the oscillation frequency of the ring oscillation circuit corresponding to the coil; Since it is equipped with means for detecting a change in the total current consumption of the plurality of ring oscillation circuits based on a change in oscillation frequency and detecting a change in the liquid level of the liquid to be measured in stages, it has a small and lightweight structure. This has the advantageous effect of allowing gradual detection of liquid level changes.

[Brief explanation of the drawing]

The attached drawings show an embodiment of the liquid level detection device according to the present invention. Figure 1 is an electrical wiring diagram of the device of the present invention, and Figure 2 is a portion of the device of the present invention used to detect the liquid level. A sectional view, FIG. 3 is a structural diagram of the float, and FIGS. 4, 5, and 6 are diagrams for explaining the operation of the device of the present invention. 100...detection circuit section, 110, 120, 13
0...Ring oscillation circuit, 114, 124, 13
4... Coil, 150... Display circuit section, 110... Power supply, 180... Float, 32... Conductive annular body .

Claims (1)

[Claims] 1. A float that responds to changes in the level of the liquid to be measured; a plurality of ring oscillation circuits each having a coil as one component and each of the coils being arranged at a predetermined liquid level detection level; a conductive annular body that is magnetically coupled to one of the coils to change the oscillation frequency of the ring oscillation circuit corresponding to the coil; and the plurality of ring oscillations based on the change in the oscillation frequency of the ring oscillation circuit. A liquid level detection device comprising: means for detecting a change in the liquid level of the liquid to be measured in stages by detecting a change in the total current consumption of the circuit.