In production, there is often a need to measure the level of liquids (water, gasoline, oil). In everyday life, most often you need to determine the height of water in a container, for this they use special devices- level gauges and alarms. Measuring devices are divided into several types; they are purchased in stores, but for home use The easiest way is to make a water level sensor with your own hands.

Types of sensors

Sensors differ in the method of measuring liquid level and are divided into two types: alarms and level meters. Alarms monitor the specified filling point of the container and, when the required volume of liquid is reached, stop its flow (for example, a float in a toilet tank).

Level gauges continuously monitor the degree of filling of the tank (for example, a sensor on a mine drainage system).

According to the principle of operation, water level sensors in the tank are divided into these varieties:

These are the most common level sensors; in addition to them, there are capacitive, hydrostatic, radioisotope and other types of devices that are used in various industries.

Selection rules

When purchasing a liquid level sensor in a tank, you need to take into account several factors; if they are observed, the device will work correctly and reliably. First of all, you need to determine type of liquid medium and its density, the level of danger to humans. What matters is the material of the container and its volume - the operating principle of the selected sensor depends on these parameters.

The next point to pay attention to is purpose of the device, it will be used to control the minimum and maximum liquid levels or to constantly monitor the filling of the tank.

When choosing industrial sensors, the number of criteria can be expanded; for household alarms and level meters, it is enough to take into account the volume of the tank and the type of device. At home, home-made devices are used - they work no worse than factory models.

DIY making

The easiest way is to make your own float sensor for the water level in the tank, or a fill indicator.

The principle of operation of such a device consists in the fact that the float floats up in the liquid, when the container is filled to its maximum, it closes the contacts and signals that the water level is sufficient.

Manufacturing sequence:

The given sensor manufacturing scheme is the simplest; it is used for small containers.

The disadvantage of such a device is that it does not allow the pump to automatically turn off. To stop the flow of water into the tank, alarms are made using magnets and reed switches.

When the need arises to control the fluid level, many do this work manually, but this is extremely ineffective, takes a lot of time and effort, and the consequences of oversight can be very expensive: for example, a flooded apartment or a burnt out pump. This can be easily avoided by using float water level sensors. These are devices that are simple in design and operating principle and are affordable.

At home, sensors of this type allow you to automate processes such as:

• monitoring the liquid level in the supply tank;
• pumping groundwater from the cellar;
• turning off the pump when the level in the well falls below the permissible level, and some others.

Operating principle of a float sensor

An object is placed in the liquid and does not sink in it. This could be a piece of wood or foam, hollow sealed plastic sphere or metal and much more. When the liquid level changes, this object will rise or fall with it. If the float is connected to the actuator, it will act as a water level sensor in the tank.

Equipment classification

Float sensors can independently monitor the liquid level or send a signal to the control circuit. According to this principle, they can be divided into two large groups: mechanical and electrical.

Mechanical devices

Mechanical valves include a wide variety of float valves for the water level in the tank. The principle of their operation is that the float is connected to a lever; when the liquid level changes, the float moves up or down this lever, and it, in turn, acts on the valve, which shuts off (opens) the water supply. Such valves can be seen in cisterns toilets. They are very convenient to use where you need to constantly add water from central system water supply

Mechanical sensors have a number of advantages:

• simplicity of design;
• compactness;
• safety;
• autonomy - do not require any sources of electricity;
• reliability;
• cheapness;
• ease of installation and configuration.

But these sensors have one significant drawback: they can control only one (upper) level, which depends on the installation location, and regulate it, if possible, then within very small limits. Such a valve can be sold called “float valve for containers”.

Electrical sensors

An electric liquid level sensor (float) differs from a mechanical one in that it itself does not shut off the water. The float, moving when the amount of liquid changes, affects the electrical contacts that are included in the control circuit. Based on these signals automatic system control makes a decision on the need for certain actions. In the simplest case, such a sensor has a float. This float acts on the contact through which the pump is turned on.

Reed switches are most often used as contacts. A reed switch is a sealed glass bulb with contacts inside. Switching of these contacts occurs under the influence magnetic field. Reed switches are miniature in size and can be easily placed inside a thin tube made of non-magnetic material (plastic, aluminum). A float with a magnet moves freely along the tube under the influence of liquid, and when it approaches, the contacts are activated. This entire system is installed vertically in the tank. By changing the position of the reed switch inside the tube, you can adjust the moment the automation operates.

If you need to monitor the upper level in the tank, then the sensor is installed at the top. As soon as the level drops below the set level, the contact closes and the pump turns on. The water will begin to increase, and when the water level reaches the upper limit, the float will return to its original state and the pump will turn off. However, in practice such a scheme cannot be used. The fact is that the sensor is triggered by the slightest change in the level, after which the pump turns on, the level rises, and the pump turns off. If the water flow from the tank is less than the supply, a situation arises when the pump is constantly turned on and off, while it quickly overheats and fails.

Therefore, water level sensors to control the pump they work differently. There are at least two contacts in the container. One is responsible for the upper level; it turns off the pump. The second determines the position of the lower level, upon reaching which the pump turns on. Thus, the number of starts is significantly reduced, which ensures reliable operation the entire system. If the level difference is small, then it is convenient to use a tube with two reed switches inside and one float that connects them. With a difference more than a meter two separate sensors are used, installed at the required heights.

Despite more complex design and the need for a control circuit, electric float sensors make it possible to fully automate the liquid level control process.

If you connect light bulbs through such sensors, then they can be used for visual control amount of liquid in the tank.

Homemade float switch

If you have the time and desire, then you can make a simple float water level sensor with your own hands, and the costs for it will be minimal.

Mechanical system

In order to simplify as much as possible design, we will use a ball valve (faucet) as a locking device. The smallest valves (half-inch or smaller) work well. This type of faucet has a handle that closes it. To convert it into a sensor, you need to extend this handle with a strip of metal. The strip is attached to the handle through holes drilled in it with the appropriate screws. The cross-section of this lever should be minimal, but it should not bend under the influence of the float. Its length is about 50 cm. The float is attached to the end of this lever.

As a float you can use two liter plastic bottle from soda. The bottle is half filled with water.

You can check the operation of the system without installing it in the tank. To do this, install the faucet vertically and place the lever with the float in a horizontal position. If everything is done correctly, then under the influence of the mass of water in the bottles, the lever will begin to move down and take a vertical position, and the valve handle will turn with it. Now submerge the device in water. The bottle should float up and turn the valve handle.

Since valves vary in size and the amount of force required to switch them, the system may need to be adjusted. If the float cannot turn the valve, you can increase lever length or take a larger bottle.

We mount the sensor in the container at the required level in a horizontal position, while in the vertical position of the float the valve should be open, and in the horizontal position it should be closed.

Electric type sensor

For self-production of the sensor this type, except regular tool, you will need:

The manufacturing sequence is as follows:

When the liquid level changes, the float moves along with it, which acts on an electrical contact to control the water level in the tank. A control circuit with such a sensor may look like the one shown in the figure. Points 1, 2, 3 are the connection points for the wire that comes from our sensor. Point 2 is a common point.

Let's consider the principle of operation homemade device. Let's say at the moment of switching on the tank empty, the float is in the low level position (LL), this contact closes and supplies power to the relay (P).

The relay operates and closes contacts P1 and P2. P1 is a self-locking contact. It is needed so that the relay does not turn off (the pump continues to work) when the water begins to rise and the contact of the low pressure unit opens. Contact P2 connects the pump (H) to the power source.

When the level rises to the upper value, the reed switch will operate and open its contact VU. The relay will be de-energized, it will open its contacts P1 and P2, and the pump will turn off.

As the amount of water in the tank decreases, the float will begin to fall, but until it takes the lower position and closes the NU contact, the pump will not turn on. When this happens, the work cycle will repeat again.

This is how a water level control float switch works.

During operation, it is necessary to periodically clean the pipe and float from dirt. Reed switches can withstand a huge number of switchings, so this sensor will last for many years.

Country house. Well with pump + storage tank. If you are too lazy to turn on the pump, then you need an automatic switch. The task is as follows: it is necessary to turn on the pump in the well when the water in the storage tank (for example, a barrel) drops below a certain level, and turn off the pump when the water fills up.
Storage containers come in different sizes. Wells are also different. You can inadvertently drain the well if you do not turn off the pump in time. And the pump itself is also not accustomed to working without water.
Therefore, you also need to be able to temporarily turn off the pump in the well if the level has dropped and allow it to turn on if the level is normal.

There are many on the Internet electronic circuits monitoring the upper and lower water levels. From simple ones (a couple of transistors) to microprocessor ones. We will not consider them. The principle of electrical conductivity of water is very often used as a water level sensor. Those. These are, as a rule, electrodes in direct contact with water. The downside is that they tend to oxidize, lose contact with wires, and other benefits of having a “piece of hardware under potential” in water.

This article discusses the implementation of a contactless sensor from scrap materials.
After my pump failed to turn on once again, I decided to make something more original as a sensor than three pieces of iron in the water.

To make one such sensor you will need:
- Polypropylene pipe for water with an internal diameter of 25mm. A pipe made of metal-plastic is not advisable, because... it can be accidentally deformed quite easily, but if you are careful, you can do it.
- A pair of door opening sensors (we remove two reed switches and a magnet from them)

- Cork stopper from a bottle (wine or other suitable one). The contents of the bottle are not so important, the main thing is that it does not interfere with further work.
- A wire of the required length, heat-shrink tubing, a pair of nylon ties, string and electrical tape.

In general, there was nothing in short supply, everything was found in the barn.

The first thing you need to do is drill (pick) a hole in the end of the plug to insert a magnet inside.
After the magnet is inserted, you need to check that the plug flies freely inside the pipe. Most likely this is not the case. Therefore, by rubbing the cork against a file or sandpaper, we reduce the diameter of the cork.
It should look something like this:

For better sliding inside the pipe, the cork can be coated with varnish (for example, yacht varnish) using the dipping method.
Because The varnish will add some thickness to the cork; you need to adjust the diameter of the cork with a margin. My diameter of the cork along with the varnish coating is smaller internal diameter pipes by about 3 mm.

Next, we solder the obtained reed switches to the wires, place them in heat shrink and encase it. The distance between the reed switches corresponds to the difference between the lower water level in the well (when the pump needs to be turned off in an emergency) and the upper level when it is allowed to be turned on again.

To prevent water from penetrating inside, the top edge of the heat shrink should go over the wire and grip it tightly. Therefore, it is better to use a round wire.

The heat shrink should go from the wire suitable to the sensor over both reed switches and end approximately 5 cm after the lower reed switch.
We make the lower edge of the heat shrink about 5 cm larger than necessary and after shrinking we bend the tail upward, fixing it in this position, for example, with another piece of heat shrink.

We collect. Heat-shrinkable reed switches are attached along the tube using any convenient method (nylon ties or electrical tape). When using screeds, it must be taken into account that cold water they can shrink and either burst themselves or damage something. Therefore, you should not tighten them too much.

There is exactly the same limiter on top so that the plug does not float out of the pipe. The limiters must be placed in such a way that, when resting against them, the plug is opposite the reed switch.
Like that:

The assembled structure needs to be tied to a rope and can be used.
It turns out like this:

Before lowering it into the well, we connect everything to the pump control device and check its functionality by turning the pipe over.
The plug should move freely and when it reaches the reed switches, turn the pump off/on.

We lower the pipe into the well to the end (the lower reed switch is just below the pump level). We turn on the pump and try to drain the well. As soon as the pump begins to gasp for air, raise the tube until the plug drops to the lower reed switch and turns off the pump.

Raise it a little higher so that the pump turns off a little earlier than the water runs out and fix it like that. Accordingly, when there is enough water in the well, the plug will turn on the upper reed switch, which allows the pump to work again.

A similar device is installed on the storage tank. It turns on the pump when the water in the tank runs out and turns off when the water is full.

True, this device has some technological features:
- The device is not located inside the container, but outside and works using the method of communicating vessels.
- In this case, you don’t have to install the upper limiter; it is enough for the pipe to be slightly higher than the top edge of the container
- It will not be possible to use two holes and a tie as a lower limiter (water will leak out). Therefore, the lower limit is the bend of the pipe.

Unfortunately, it was not possible to photograph the actual structure installed on the drive. Therefore, I will show you schematically.

We will make a simple, but very useful and effective water level indicator ourselves. And this article will help you do such a necessary and very useful thing.

First, let's look at schematic diagram this device.

Water level indicator diagram.

The scheme is very simple, but it works great. At the end of the article there will be a video that clearly shows the operation of this water level indicator, which we will make together with you.
To get started, let's collect the parts we need to make the device.

Parts for making a water level indicator circuit.

We will need:
ULN2004 chip or a similar one, a contact pad for installing the chip on the board. If there is such a platform, there is no risk of overheating the legs of the microcircuit with a soldering iron or damaging it internal organization static electricity. And circuit repair, if necessary, is reduced to a few seconds. It is enough to remove the burnt microcircuit from the socket and insert a new one in its place. A complete benefit, especially for not very experienced radio amateurs.
Resistors R1 - R7 - 47Kom.
R8 - R14 - 1Kom.
LEDs of any color of your choice, with a diameter of 3 - 5 mm.
Capacitor 100Mkf 25v.
Terminal blocks of any type, or you can do without them at all, but the ease of use of the device will decrease somewhat.
Any development board, as long as all the components fit. I use such boards because I don’t want to bother making printed circuit board, it’s just more convenient and more familiar to me.

We have all assembled the components and are ready to begin manufacturing our device.

We place some components on the board.
We immediately solder the installed parts, otherwise they will constantly jump out of their sockets.

Sealing parts one by one.
We install the following details of the circuit.

There is no system, work as it is more convenient and easier for you.

You just need to constantly check the diagram, no matter how simple it is. Anyone can get confused, but you don’t want to redo work that’s already been done.

Accuracy and attentiveness are also not superfluous.

And so on in order. We install the part, solder it and move on to the next one.

We are approaching the finish line.

I installed LEDs with reverse side board only because this water level indicator circuit block will be installed in the control panel on the front panel. The panel will be drilled for the LEDs, and the outline of the container will be drawn on the outside. And the amount of water will be clearly displayed on the board. The board will be secured with four bolts into the existing holes.

This is the first ready-made element of a future water purification system from iron, bacteria, all sorts of harmful impurities and other “poop”. The system has been working at my home for almost three years now, it has proven to be reliable, convenient, and in general I like it. I am completely satisfied with the quality of the water. But the time has come for modernization. New requirements have appeared (for me), I want more convenient service, I want all the information about the operation of the system to be constantly in front of my eyes. I built the first water purification system without any experience and made some mistakes, which I will certainly write about in future articles, but overall there were only two minor breakdowns. I was to blame for one breakdown, and for another it was a poor quality component (again I was to blame, I saved a little and bought the wrong thing).

All equipment will be modular (this increases the possibility of modernization and simplifies repairs), as cheap and simple as possible, so that many can repeat it.

I’ll tell you why white wires are needed in one of the following articles.
The water level indicator (alarm) is ready.

The cable that goes to the level sensors can be any eight-wire signal cable; they are now sold in all sorts of different stores that deal with alarms and electrical systems. The cross-section of the cores and the length of the cable do not play a special role. There are cables that are very thin and cheap.

How to make level sensors needs to be thought out and manufactured according to the place of application. It is best to make the sensor contacts from stainless steel. The positive common electrode needs a massive one. I made it from a small stainless spoon, the electrode works fine and is not at all susceptible to electrochemical dissolution. The places where the wires are soldered to the electrodes are best insulated with the help of any glue gun (reliably preserved from dissolution).

However, if you power the circuit using a button without locking, then there will be no dissolution. You need to see how much water there is - press the button. I released it and the power to the circuit turned off. At the dacha, the circuit can be powered from batteries or AA batteries connected in series and with a button (enough for a long period) or from an old battery. This device not demanding on supply voltage.

Good luck to you.

To automate many production processes it is necessary to control the water level in the tank; the measurement is carried out using a special sensor that gives a signal when the process medium reaches a certain level. It is impossible to live without level meters in everyday life; a striking example of this is shut-off valves toilet cistern or automatic system to turn off the well pump. let's consider different kinds level sensors, their design and operating principle. This information will be useful when choosing a device for specific task or making a sensor yourself.

Design and principle of operation

Design of measuring devices of this type determined by the following parameters:

• Functionality, depending on this device, is usually divided into alarms and level meters. The former monitor a specific tank filling point (minimum or maximum), while the latter continuously monitor the level.
• The operating principle can be based on: hydrostatics, electrical conductivity, magnetism, optics, acoustics, etc. Actually, this is the main parameter that determines the scope of application.
• Measuring method (contact or non-contact).

In addition, the design features are determined by the nature of the technological environment. It's one thing to measure height drinking water in the tank, another is to check the filling of industrial wastewater tanks. In the latter case, appropriate protection is necessary.

Types of level sensors

Depending on the principle of operation, alarms are usually divided into the following types:

• float type;
• using ultrasonic waves;
• devices with a capacitive level detection principle;
• electrode;
• radar type;
• working on the hydrostatic principle.

Since these types are the most common, let's look at each of them separately.

Float

This is the simplest, but nevertheless effective and reliable way measuring liquid in a tank or other container. An example implementation can be found in Figure 2.

Rice. 2. Float sensor for pump control

The design consists of a float with a magnet and two reed switches installed at control points. Let us briefly describe the principle of operation:

• The container is emptied to a critical minimum (A in Fig. 2), while the float drops to the level where reed switch 2 is located, it turns on the relay that supplies power to the pump pumping water from the well.
• The water reaches the maximum level, the float rises to the location of reed switch 1, it is triggered and the relay is turned off, accordingly, the pump motor stops working.

It’s quite easy to make such a reed switch yourself, and setting it up comes down to setting on-off levels.

Note that if you choose the right material for the float, the water level sensor will work even if there is a layer of foam in the tank.

Ultrasonic

This type of meter can be used for both liquid and dry media and may have an analogue or discrete output. That is, the sensor can limit the filling upon reaching a certain point or monitor it continuously. The device includes an ultrasonic emitter, receiver and signal processing controller. The operating principle of the alarm is demonstrated in Figure 3.

Rice. 3. Operating principle of ultrasonic level sensor

The system works as follows:

• an ultrasonic pulse is emitted;
• the reflected signal is received;
• The duration of signal attenuation is analyzed. If the tank is full, it will be short (A Fig. 3), and as it becomes empty it will begin to increase (B Fig. 3).

The ultrasonic alarm is non-contact and wireless, so it can be used even in aggressive and explosive environments. After initial setup, such a sensor does not require any specialized maintenance, and the absence of moving parts significantly extends its service life.

Electrode

Electrode (conductometric) alarms allow you to monitor one or more levels of an electrically conductive medium (that is, they are not suitable for measuring the filling of a tank with distilled water). An example of using the device is shown in Figure 4.

Figure 4. Liquid level measurement with conductometric sensors

In the example given, a three-level alarm is used, in which two electrodes control the filling of the container, and the third is an emergency one to turn on the intensive pumping mode.

Capacitive

Using these alarms, it is possible to determine the maximum filling of the container, and both liquid and bulk solids of mixed composition can act as the process medium (see Fig. 5).

Rice. 5. Capacitive level sensor

The operating principle of the alarm is the same as that of a capacitor: the capacitance is measured between the plates of the sensitive element. When it reaches the threshold value, a signal is sent to the controller. In some cases, a “dry contact” design is used, that is, the level gauge operates through the tank wall in isolation from the process medium.

These devices can operate in a wide range temperature range, they are not affected by electromagnetic fields, and operation is possible on long distance. Such characteristics significantly expand the scope of application up to severe operating conditions.

Radar

This type of alarm device can truly be called universal, since it can work with any process environment, including aggressive and explosive ones, and pressure and temperature will not affect the readings. An example of how the device works is shown in the figure below.

The device emits radio waves in a narrow range (several gigahertz), the receiver catches the reflected signal and, based on its delay time, determines how full the container is. The measuring sensor is not affected by pressure, temperature or the nature of the process fluid. Dustiness also does not affect the readings, which cannot be said about laser alarms. It should also be noted high accuracy devices of this type, their error is no more than one millimeter.

Hydrostatic

These alarms can measure both maximum and current filling of tanks. Their operating principle is demonstrated in Figure 7.

Figure 7. Fill measurement with gyrostatic sensor

The device is built on the principle of measuring the level of pressure produced by a column of liquid. Acceptable accuracy and low cost made this type quite popular.

Within the scope of the article, we cannot examine all types of alarms, for example, rotary-flag ones, for identifying granular substances (a signal is sent when the fan blade gets stuck in a granular medium, after first tearing out the pit). It also makes no sense to consider the principle of operation of radioisotope meters, much less recommend them for checking the level of drinking water.

How to choose?

The choice of a water level sensor in a tank depends on many factors, the main ones:

• Composition of the liquid. Depending on the content of foreign impurities in the water, the density and electrical conductivity of the solution may change, which is likely to affect the readings.
• The volume of the tank and the material from which it is made.
• The functional purpose of the container is to accumulate liquid.
• The need to control the minimum and maximum level, or monitoring of the current state is required.
• Admissibility of integration into an automated control system.
• Switching capabilities of the device.

This is far from full list for selection measuring instruments of this type. Naturally, for household use the selection criteria can be significantly reduced by limiting them to tank volume, type of actuation and control circuit. Significant reduction in requirements makes it possible self-production similar device.

Making a water level sensor in a tank with your own hands

Let's say there is a task to automate work submersible pump for water supply to the dacha. Typically, water enters storage capacity Therefore, we need to make sure that the pump turns off automatically when it fills. It is not at all necessary to buy a laser or radar level indicator for this purpose; in fact, you don’t need to purchase any. A simple task requires simple solution, it is shown in Figure 8.

To solve the problem, you will need a magnetic starter with a 220-volt coil and two reed switches: a minimum level for closing, a maximum level for opening. The pump connection diagram is simple and, importantly, safe. The principle of operation was described above, but let’s repeat it:

• As the water collects, the float with the magnet gradually rises until it reaches the maximum level reed switch.
• The magnetic field opens the reed switch, turning off the starter coil, which leads to de-energization of the engine.
• As the water flows, the float drops until it reaches the minimum mark opposite the lower reed switch, its contacts close, and voltage is supplied to the starter coil, which supplies voltage to the pump. Such a water level sensor in a tank can work for decades, unlike electronic system management.