Hello! Many people know firsthand about such a measuring device as a pressure gauge. But many people find it difficult to imagine the device and the principle of its operation.
A pressure gauge is designed to measure the pressure of a liquid or gas. Moreover, the pressure gauge for measuring gas and liquid pressure is not structurally different 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 and works, look at the figure below.
The pressure gauge consists of a body with a measurement scale, a copper flat tube 1 folded in the shape of a circle, a fitting 2, a transmission mechanism 3 from the tube to the pointer 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.
When gas and liquid under pressure are supplied through fitting 2, the folded tube 1 will tend to straighten, and through the transmission mechanism the movement of the tube will be transmitted to the arrow 4. It, in turn, will indicate the amount of pressure, which can be read using a scale. When the pressure decreases, the tube will collapse again and the arrow will indicate a decrease in pressure.
I think you can guess how an electric contact pressure gauge works. Its design is no different from a conventional pressure gauge, except that it has built-in contacts. There are usually two of them and their position on the pressure gauge scale can be changed.
What if you don’t have an electrical contact pressure gauge, but you really need one? What to do then? Then you need to make a homemade electric contact pressure gauge.
I'll tell you how to make a homemade electric contact pressure gauge. To do this, you will need a simple pressure gauge, two small strips of tin from a tin can, double-sided tape and two thin wires.
Using a sharp awl, pry up and remove the large retaining ring. Then remove the glass and then the rubber washer. Drill two holes in the pressure gauge housing to allow two wires to pass through them.
Cut two strips from 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.
Reinstall the rubber gasket and then the glass. Secure everything with a locking ring. That's it, the homemade electric contact pressure gauge is ready. For example, I used this one in a homemade automatic system water supply of a private house.
In order for this pressure gauge to influence any actuator, a special circuit is needed. You can see an example of this scheme in the figure below.
At a minimum pressure of the medium (gas or liquid) in the electric contact pressure gauge, contacts 1 and 2 will be closed. In this case, the electromagnetic relay K1 will operate. It, in turn, with its contacts K1.1 will supply power to the winding of the magnetic starter K3. Using contacts K3.1, it will bypass contacts K1.1, and when the contacts in pressure gauge 1 and 2 open, relay K1 will release its contacts K1.1. But at the same time, the starter winding K3 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. At the same time, the electromagnetic relay K2 will operate and with its contacts will open the power circuit of the coil K3 of the magnetic starter. Contacts K3.2 will open and the power supply to motor M will disappear. With a further decrease in pressure and the closure of pressure gauge contacts 1 and 2, the cycle will repeat.
...I decided to write a strange post. Somehow, a post about making a pressure gauge caught my eye. Or rather, not the device itself, but its miniature copy. For what? For all kinds of crafts where you don’t need to use these devices (and it’s unlikely that they can be found in this size).
MANOMETER (from the Greek manos - loose and metron - measure, metreo - measure), a device for measuring liquid and gas pressure. Depending on the design of the sensitivity of the element, there are liquid, piston, deformation and spring pressure gauges (tubular, membrane, bellows);
dependencies of some are also used physical quantities(e.g. electric current) from pressure. There are absolute pressure gauges - they measure absolute pressure (from zero), pressure gauges overpressure- measure the difference between the pressure in any system and atmospheric pressure, barometers, differential pressure gauges, vacuum gauges.
A “cork” is cut out of the elastic using a tube. Later, we will need it as a backing for the pressure gauge scale.
We cut the tubes to the diameter we need. One tube is slightly larger - this will be our body. The second tube is smaller. It will serve as a stopper for the back wall on one side and the glass on the other.
We make the elastic band the thickness on which we want to place the instrument scale.
Cut out the image of the desired scale, suitable in size. I made the scales in advance. I collected pictures from the network, removed everything unnecessary, and made several images of the same scale. different sizes and printed it at the nearest photo kiosk.
For glass we take any transparent plastic. I used a CD box. We cut a circle along the inner diameter of the wide tube with side cutters. We adjust it with a file. The glass should fit very tightly, then glue will not be needed.
We make it from a brass plate back wall. It should be the same diameter as the glass.
Let's start assembling the product. First, glue the back wall to the end of the smaller tube. Then we glue the tubes so that one is in the other, while the bottom should be at the same level as the end of the larger tube. Drill a hole in the body.
IN drilled hole We insert the wire, on both sides of which we place the halves of our substrate, Glue it.
We use thinner wire to make a decorative ring that will hide the edges of the paper scale.
Shorten the second hand from wristwatch before suitable sizes and glue it onto the scale.
This is what the back side of our device looks like. You can put a shorter thin tube on the wire coming out of it. The part of the wire not covered by the tube will later be inserted into the tank (or into that part of your craft on which you plan to install this dummy).
All that remains is to sand the body and insert the glass.
You can simplify the task by using these nuts as a housing.
Result.
Pressure gauges– instruments for measuring the pressure of liquids or gases – there are different designs. You can do a simple measurement of air pressure, for example in a car or bicycle inner tube, with your own hands. Depending on the power of the spring and the strength of the housing, it can also be used to measure oil pressure. It is suitable for school experiments in physics lessons. Plus, you can do it with your children.
You will need
Take a disposable syringe and push the plunger out of it to the limit. Cut the piston rod so that a piece about 1 cm long remains. Heat the remaining piece of the rod using gas burner and melt one of the ends of the coil spring into it.
Insert the plunger back into the syringe barrel so that a small piece of the spring remains outside and the larger part is inside the balloon.
Warm up the needle and pierce the syringe barrel with it from the side opposite the tip, not far from the edge. Using pliers, attach the end of the spring to the needle. Bite off the excess part of the spring. The result is a spring pressure gauge.
If you place a rubber tube instead of a needle at the tip of the syringe and connect it to the container or pipeline in which the pressure is measured, the piston in the container will move relative to the graduation scale on the syringe body, thus indicating the pressure in the line or container being tested.
It is recommended to first calibrate the scale against a known pressure source. Link the scale to pressure units based on the reference source. To do this, pick up the phone from transparent material and fill it with water to a certain height. On the other side, connect a rubber tube with a pressure gauge. Mark the scale according to the height of the water column using Torricelli's law. At the place where the piston moved, make a mark of the resulting pressure. After changing the amount of water in the tube, make the following marks.
U-shaped pressure gauge is 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 pressure gauge have the same length.
Depending on what type of pressure is being measured, the tubes of the U-shaped pressure gauge may be open, then the liquid will be exposed 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 on them is the same.
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" column is exposed to atmospheric pressure, the pressure gauge actually shows the difference between the applied pressure and the atmospheric pressure. When dealing with a U-tube pressure gauge, the shift in levels in both columns must be taken into account when measuring pressure.
The pressure gauge scale allows you to determine the height of liquid columns in the tubes. Most pressure gauge scales have a correction 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. The position of the scale is then 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 performed in order to ensure the accuracy of the measurements taken, provided that measuring device It works well and the fluid used in it is of sufficient purity.
Proper functioning of the vehicle's fuel system is the key to the safety of the driver and passengers. Determining the volume of air in it allows you to control uninterrupted operation and troubleshoot problems in a timely manner. Pressure is checked using pressure gauges. These devices are quite simple in design and operation, so making them yourself is not difficult.
A pressure gauge is a device designed to measure fuel pressure. If this indicator is unstable, it will not be possible to properly operate the engine. Interruptions in the functionality of the engine increase fuel consumption and also affect the service life of the equipment as a whole. The vehicle's technical condition is monitored by a built-in computer ( electronic unit controls), covering and checking the pressure in the fuel rail.
It controls engine power, fuel consumption, and if one of the systems malfunctions, it displays errors on the on-board computer in the form of an encrypted code, which is not entirely convenient.
The operation of the ECU 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 monitor the operation of the fuel supply system and eliminate or eliminate such a defect in the shortest possible time.
Meter specifications:
The base of the device is a hollow hose with an oval or ellipsoidal cross-section and an elastic structure. The fuel presses with its mass on it and deforms it. Its first end is connected to the fuel system mechanism, and the second to a meter that displays the result of the deformation on the display.
There is a spring inside the transmission mechanism that prevents backlash. 
The hollow hose has cross-sectional planes of different diameters inside and outside, therefore, being under pressure, it constantly tries to level out. The end connected to the display moves the needle along 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 ability to connect in parallel to the system without stopping its operation. This allows you to take measurements while the engine is running.
There are 2 types of pressure gauges for measuring fuel pressure:
Depending on the type of action, the devices differ in the design of the sensing element:
When choosing which pressure gauge to use, you should pay attention to the following factors:
To control air exchange in the fuel system, both analog and electronic devices are used.
Analogue devices are characterized by their simple design and low cost. The data is displayed on a scale equipped with a pointer mechanism. The disadvantage is the high error when the pressure increases.
Electronic devices are more accurate and cost more. Data is displayed on the LCD screen. The user is given the opportunity to independently select the unit of measurement.
Did you know? The pressure in the fuel rail can be controlled using devices for monitoring the volume of oxygen in the tire. They work on the same principle. To accurately control the fuel system, pressure fluctuations must be within 5– 7 atmospheres. To control oxygen pressure, fluctuations vary within the range8 –16 atmospheres.
The meter scale should be readable, with limit values of 5–6 kgf/cm2. Before purchasing, check the connections for leaks and evaluate the quality of the materials. 
A 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 a car mechanic to do this. The main thing is to choose the right components. We suggest considering an option upgraded with a fuel drain valve.
When constructing a meter, the following materials will be required:
The size of the hose for refilling the air conditioner must be selected in accordance with the size of the cap, which is attached to the injector ramp. The cap is easily removed, so you can take it with you when you go shopping.
Important! The pressure gauge must be checked for errors before starting work in order to be able to replace it in time.
Tools you will need:
Step-by-step instructions for making a pressure gauge for measuring fuel pressure:
A car pressure gauge is necessary to measure the movement of air in the fuel rail. Such a device is easy to assemble yourself, and this will make it possible to constantly monitor the performance of the fuel system.
