Make your own low pressure gas pressure gauge. U-Gauge: Detailed in Plain Language

Pressure gauges- devices for measuring the pressure of liquids or gases - come in different designs. A simple measurement of air pressure, for example, in a car or bicycle chamber, can be done by hand. Depending on the power of the spring and the strength of the housing, they can also measure the oil pressure. It is suitable for school experiments in physics lessons. Plus, you can make it with your kids.

You will need

• - Disposable syringe
• - Metal spring, the diameter of which is equal to the diameter of the syringe balloon
• - Needle
• - Alcohol or gas burner
• - Glue "Moment"
• - Pliers
• - Wire cutters

Instruction

Take a disposable syringe and pull the piston out of it to the limit. Cut off the piston rod so that a piece about 1 cm long remains. Heat the remaining piece of the piston rod with a gas burner and melt one end of the coil spring into it.

Insert the plunger back into the syringe balloon so that a small piece of the spring remains on the outside, and most of it is inside the balloon.

Warm up the needle and pierce the syringe balloon with it from the side opposite the tip, near the edge. Using pliers, attach the end of the spring to the needle. Bite off the rest of the spring. Got a spring pressure gauge.

If you put a rubber tube instead of a needle on the side of the syringe tip and connect it to the container or pipeline in which the pressure is measured, the piston in the cylinder will move relative to the division scale on the syringe body, thus indicating the pressure in the line or container under test.

It is recommended to first calibrate the scale to a known pressure source. Link the scale to pressure units according to the reference source. To do this, take a tube of transparent material and fill it with water to a certain height. On the other hand, connect the rubber tube to the pressure gauge. Mark the scale according to the height of the water column according to Torricelli's law. In the place where the piston has moved, make a mark of the resulting pressure. After changing the amount of water in the tube, make the following marks.

Hello! Many people know firsthand about such a measuring device as a pressure gauge. But many find it difficult to imagine the device and the principle of its operation.

The pressure gauge is designed to measure the pressure of a liquid or gas. Moreover, the manometer for measuring the pressure of gas and liquid does not structurally differ from each other. So if you have a pressure gauge lying around somewhere to measure liquid pressure, then you can safely use it to measure gas pressure and vice versa.

To better understand how the pressure gauge works, look at the figure below.

The pressure gauge consists of a body with a measurement scale, a copper flat tube 1 rolled up in the shape of a circle, a fitting 2, a transmission mechanism 3 from the tube to the arrow 4. Using the fitting, the pressure gauge is wrapped in a vessel where the pressure of the medium (gas or liquid) is to be measured.

How a manometer works

When gas and liquid under pressure are supplied through fitting 2, the rolled tube 1 will tend to straighten out, while through the transmission mechanism the movement of the tube will be transmitted to the arrow 4. It, in turn, will indicate the pressure value, which can be read using the scale. When the pressure decreases, the tube will again curl up and the arrow will indicate a decrease in pressure.

Electrocontact pressure gauge device

How the electrocontact pressure gauge works, I think you guessed it yourself. It does not differ in any way from a conventional pressure gauge, only with the exception that it has built-in contacts. There are usually two of them and their position on the pressure gauge scale can be changed.

And if you do not have an electrocontact pressure gauge, but you really need it? What to do then? Then you need to make a homemade electrocontact pressure gauge.

I will tell you how to make a homemade electrocontact pressure gauge. To do this, you will need a simple pressure gauge, two small strips of tin from a can, double-sided tape and two thin wires.

Use a sharp awl to pry and remove the large retaining ring. Then remove the glass and then the rubber washer. Drill two holes in the gauge body to allow two wires to pass through.

Cut two strips from the tin and bend them in the shape of the letter L. Solder a thin insulated wire to the base. From double-sided tape, cut two strips equal in size to the strips and stick it on the strips. Next, glue the resulting contacts to the pressure gauge scale within the specified pressure limits.

Pass the wires through the holes and bring them out.

Replace the rubber gasket and then the glass. Secure everything with a retaining ring. Everything, a home-made electrocontact pressure gauge is ready. For example, I used this one in a home-made automatic water supply system for a private house.

Wiring diagram for electrocontact pressure gauge

In order to act on any actuator with this pressure gauge, a special circuit is needed. You can see an example of this circuit in the figure below.

At the minimum pressure of the medium (gas or liquid) in the electrocontact pressure gauge, contacts 1 and 2 will be closed. In this case, the electromagnetic relay K1 will work. It, in turn, with its contacts K1.1 will supply power to the winding of the magnetic starter K3. With contacts K3.1, it will shunt contacts K1.1, while opening the contacts in the pressure gauge 1 and 2, relay K1 releases its contacts K1.1. But at the same time, the winding K3 of the starter will continue to flow around with current. With its contacts K3.2, the magnetic starter will supply power to the motor M of the pump or compressor.

With a further increase in pressure in the pressure gauge, contacts 1 and 3 close. In this case, the electromagnetic relay K2 will operate and open the power supply circuit of the coil K3 of the magnetic starter with its contacts. Contacts K3.2 will then open and the power supply to the motor M will disappear. With a further decrease in pressure and the closure of the pressure gauge contacts 1 and 2, the cycle will repeat.

How to measure the pressure at the outlet of the reducer:

Those who tried to purchase a pressure gauge for measuring low pressure know that it is not so easy to do this, and the price for them is not small, 2000-3000 rubles.
How to measure the gas pressure at the outlet of the reducer?
In this article we will tell you about several, fairly budgetary, ways.

Method number 1:
Pressure measurement with a U-shaped manometer

U A -shaped manometer is a liquid manometer consisting of communicating vessels in which the measured pressure is determined from one or more liquid levels.
IN U-shaped glass pressure gauges, the free end of the tube communicates with the atmosphere, and the measured pressure is applied to the other end. The simplest scheme for measuring pressure with a liquid glass manometer is shown in the figure:

Atmosphere pressure P atm acts on one end U-shaped tube partially filled with working fluid. The other end of the tube is connected to the area of ​​the measured pressure using various types of supply devices. P abs. At R abs > R atm, the liquid in the part of the measured pressure supplied will be displaced into the part connected to the atmosphere. As a result, between the levels of liquids located in different parts U-shaped tube, a liquid column is formed, height h- measured overpressure.

The figure shows U-shaped liquid glass manovacuummeter. U-shaped glass tube 1 is fastened with brackets 2 on a metal or wooden base 3. On it, between the two tubes, there is a scale plate 4 with applied linear markings. The tube is filled with working fluid to the zero mark relative to the scale plate. The bulges at the ends of the glass tube are designed for tighter connection of rubber hoses.

When measuring overpressure to one end U-shaped tube is supplied with the measured pressure medium. The second exit remains free and communicates with the atmosphere. A similar situation occurs when measuring vacuum pressure. The symmetry of the linear markings on the scale plate ensures the applicability of the device for measuring excess and (or) vacuum pressure.
U-shaped liquid manometers with water as a working liquid can be used as pressure gauges, thrust gauges and draft gauges for measuring the pressure of air, non-aggressive gases in the range of ±10 kPa (100 mbar).

You can buy a ready-made manometer with a glass tube. Also, this pressure gauge can be made on its own, using a transparent PVC tube and a ruler.
Naturally, the readings of this pressure gauge will be in mm. water column. To convert them to another value, use the converter at the end of this page.

Method number 2:
Measuring pressure with a household blood pressure monitor

Blood pressure can be measured with a household blood pressure monitor.

1. Take a blood pressure monitor (not a full machine, but one in which the cuff is inflated with a rubber bulb).

2. Disconnect the pear and pick up a piece of hose that will act as an adapter between the reducer and the tonometer hose.

3. Connect the outlet of the reducer to the hose of the tonometer (the valve on the cylinder must be closed)

4. Clamp the hose leading to the cuff (you can use a clamp, a small vise, or, folding the hose several times, pull it with a thread).

5. Press the "Start" button on the tonometer. The tonometer will calibrate and in a few seconds it will be ready for measurement, the display will show “0”

6. Open the valve on the cylinder, the tonometer will show the outlet pressure of the reducer in mm. mercury column. Pay attention to the cuff, it should not inflate.

7. CLOSE VALVE ON CYLINDER.

If you have an adjustable reducer and you need to set a certain pressure, follow these steps:
- in the converter of values, enter the required value in millibars
- determine the corresponding value in mm. mercury column
- press the start button on the tonometer, the tonometer will calibrate and in a few seconds it will be ready for measurement, the display will show “0”
- open the valve on the cylinder, the tonometer will show the outlet pressure of the reducer in mm. mercury column
- by adjusting the reducer, set the value you need.
- close the valve on the cylinder

ATTENTION!
Do not use the tonometer for continuous (continuous) measurement of gas pressure.
The materials of which the tonometer is made are not intended for long-term contact with LPG.

Gas Converter:

Soon we will tell you about another simple and inexpensive way to measure low pressure.

The correct functioning of the fuel system of the car is a guarantee of the safety of the driver and passengers. Determining the volume of air in it allows you to control the smooth operation and timely troubleshoot. Pressure check is carried out by manometers. These devices are quite simple in design and operation, so making them yourself is not difficult.

Purpose and technical parameters

A manometer is a device designed to measure fuel pressure. If this indicator is unstable, then it will not be possible to properly adjust the operation of the engine. Interruptions in the functionality of the motor increase fuel consumption, and also affect the duration of operation of the equipment as a whole. The control of the technical condition in the car is carried out by the built-in ECU (electronic control unit), including checking the pressure in the fuel rail.

It controls the power of the engine, the amount of fuel consumption, and if one of the systems malfunctions, it issues errors to the on-board computer in the form of an encrypted code, which is not very convenient.

The operation of the computer is not always stable, and with several deviations in the functionality of the car, it can be difficult to immediately determine the breakdown. At the same time, the pressure gauge will make it possible to control the operation of the fuel supply system and eliminate or eliminate such a defect as soon as possible.

Specifications of the meter:

• control of excess pressure of non-crystallizing liquid, gas, steam;
• accuracy class - 1–2.5;
• measurement range - 5–8 A.

How does it work

The basis of the device is a hollow hose with an oval or ellipsoidal section, elastic structure. The fuel presses its mass on it and deforms it. Its first end is connected to the mechanism of the fuel system, and the second - to the meter, which displays the result of the deformation on the scoreboard.

Inside the transmission mechanism there is a spring that prevents the backlash.

A hollow hose has a section plane of different diameters inside and outside, therefore, being under pressure, it tries to level out all the time. The end connected to the display advances the arrow on the scale. At a maximum pressure of 25 bar and below, the accuracy of the device will be 2.5, more than 25 bar - 1.5.

The advantage of the device is the possibility of parallel connection to the system without stopping its operation. This allows you to take measurements while the engine is running.

Varieties

There are 2 types of pressure gauges for measuring fuel pressure:

• analog;
• electronic.

According to the type of action, the devices differ in the device of the sensitive element:

• liquid;
• membrane;
• spring;
• bellows;
• piston;
• piezoelectronic;
• radioactive;
• wire.

What to look for when buying

When choosing which pressure gauge to use, you should pay attention to such factors:

• device device;
• technical specifications.

Both analog and electronic devices are used to control air exchange in the fuel system.

Analog devices are characterized by simple design and low cost. The data is displayed on a scale equipped with a pointer mechanism. The disadvantage is the high error when increasing the pressure.

Electronic devices are more accurate and cost more. The data is displayed on the LCD screen. The user is given the opportunity to independently select the unit of measurement.

Did you know? The fuel rail pressure can be controlled using devices to monitor the amount of oxygen in the tire. They work on the same principle. For accurate control of the fuel system, pressure fluctuations must be within 5– 7 atmospheres. To control oxygen pressure, fluctuations vary in the range8 -16 atmospheres.

The scale of the meter should be legible, with limit values ​​​​of 5-6 kgf / cm 2. Before buying, check the connection for tightness, evaluate the quality of the materials.

How to DIY

The pressure gauge for diagnosing the fuel system can be assembled with your own hands, spending a minimum of money. You don't have to be an auto mechanic to do this. The main thing is to choose the right components. We propose to consider a variant upgraded with a tap for draining fuel.

Tools and materials

When constructing the meter, the following materials will be required:

• hose for filling air conditioners with a fitting;
• tee with 1/4 thread;
• 2 fittings with a bore diameter of 6 mm;
• tap with 1/4 thread;
• manometer with a user-friendly scale for 6 atmospheres.

The size of the hose for filling the air conditioner must be selected in accordance with the size of the cap, which is fixed on the nozzle rail. The cap is easy to remove, so you can take it with you when you go shopping.

Important! Checking the pressure gauge for error must be carried out before starting work in order to be able to replace it in time.

From the tools you will need:

• fumlenta for sealing joints;
• hose clamp;
• compressor to check the accuracy of the pressure gauge.

Homemade fuel pressure gauge: video

Manufacturing process

Step-by-step instructions for making a pressure gauge for measuring fuel pressure:

1. Screw the tee to the manometer.
2. Attach a faucet to the tee.
3. Attach fittings to the faucet.
4. Seal each joint with tape.
5. Cut the hose. Attach the cut end to the lower fitting on the faucet, strengthen the structure with a clamp.

A car pressure gauge is needed to measure the movement of air in the fuel rail. Such a device is easy to assemble on your own, and this will make it possible to constantly monitor the performance of the fuel system.

U-shaped pressure gauge - a device for measuring pressure, which consists of a transparent tube, made in the shape of the Latin letter "U". The sides of such a manometer have the same length.

Depending on what kind of pressure is being measured, the tubes of the U-gauge can be opened, then the liquid will be subject to atmospheric pressure. The tubes can also be closed and connected to a pressure source. If both ends of the tube are open, the liquid levels in both columns are the same because the pressure is the same on them.

Working principle of U-gauge

When pressure is applied to column "B" of the manometer, the height of the liquid in column "A" increases, and the height of column "B" decreases.

Since the "A" pillar is exposed to atmospheric pressure, the pressure gauge actually shows the difference between the applied pressure and atmospheric pressure. When dealing with a U-gauge, when measuring pressure, it is necessary to take into account the offset levels in both columns.

The pressure gauge scale allows you to determine the height of the liquid columns in the tubes. Most pressure gauge scales have a corrective device to adjust the position of the scale. Before taking measurements with a pressure gauge, you should make sure that the liquid levels in the columns are the same. Then the position of the scale is adjusted so that both levels coincide with the level of the zero mark on the scale. This operation is called "zeroing" or setting the pressure gauge to zero. It is carried out in order to ensure the accuracy of the measurements made, provided that the measuring device is working properly and the liquid used in it is of sufficient purity.