How are pressure gauges made? We discuss digital homemade pressure gauges, DIY U-shaped pressure gauge
How to measure the pressure at the outlet of the reducer:
Those who tried to purchase a pressure gauge to measure low pressure, they know that this is not so easy to do, 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 budget-friendly methods.
Method No. 1:
Measuring pressure using a U-shaped pressure gauge
U-shaped pressure gauge is a liquid pressure gauge consisting of communicating vessels in which the measured pressure is determined by one or more liquid levels.
IN U In -shaped glass manometers, the free end of the tube communicates with the atmosphere, and the measured pressure is supplied to the other end. The simplest scheme measuring pressure with a liquid glass manometer is shown in the figure:
Atmospheric pressure P ATM acts on one end U-shaped tube partially filled with working fluid. The other end of the tube using various kinds supply devices connected to the measured pressure area P abs. At R abs > R atm, the liquid located in the part of the supplied measured pressure 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 column of liquid is formed, height h– measured excess pressure.
The picture shows U-shaped liquid glass pressure-vacuum gauge. U-shaped glass tube 1 is fixed to a metal or wooden base 3. On it, between 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 thickenings at the ends of the glass tube are intended for a tighter connection of rubber hoses.
When measuring excess pressure to one end U The measured pressure medium is supplied through an -shaped tube. 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 pressure gauges with water as working fluid can be used as pressure gauges, draft gauges and draft gauges for measuring air pressure, non-aggressive gases in the range of ±10 kPa (100 mbar).
You can buy a ready-made pressure gauge with glass tube. This pressure gauge can also be made on our own using 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 using a household blood pressure monitor
Pressure can be measured with a household blood pressure monitor.
1. Take a tonometer (not a fully automatic one, but one in which the cuff is inflated using a rubber bulb).
2. Disconnect the bulb and pick up a piece of hose that will act as an adapter between the reducer and the tonometer hose.
3. Connect the output of the reducer to the tonometer hose (the valve on the cylinder must be closed)
4. Clamp the hose going to the cuff (you can use a clamp, a small vice, or, after folding the hose several times, tighten it with a thread).
5. Press the "Start" button on the tonometer. The tonometer will calibrate and after a few seconds will be ready for measurement; the display will show “0”
6. Open the valve on the cylinder, the tonometer will show the output pressure of the reducer in mm. mercury. Pay attention to the cuff; it should not inflate.
7. CLOSE THE VALVE ON THE CYLINDER.
To convert the resulting value to millibars, use the converter located at the end of the page.
If you have adjustable gearbox and you need to set a certain pressure, follow these steps:
- in the unit converter, enter the required value in millibars
- determine the corresponding value in mm. mercury
- press the start button on the tonometer, the tonometer will calibrate and after a few seconds will be ready for measurement, “0” will appear on the display
- open the valve on the cylinder, the tonometer will show the output pressure of the reducer in mm. mercury
- when adjusting the gearbox, set the value you need.
- close the valve on the cylinder
ATTENTION!
Do not use the tonometer to continuously (continuously) measure gas pressure.
The materials from which the tonometer is made are not intended for prolonged contact with Liquefied Hydrocarbon Gas.
Gas unit converter:
Soon we will tell you about another simple and inexpensive way low pressure measurements
Pressure gauges– instruments for measuring the pressure of liquids or gases – there are different designs. Simple measurement of air pressure, for example in a car or bicycle camera, you can do it yourself. 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
- - Disposable syringe
- - A metal spring, the diameter of which is equal to the diameter of the syringe container
- - Needle
- - Alcohol or gas burner
- - Glue “Moment”
- - Pliers
- - Wire cutters
Instructions
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 most would be inside the cylinder.
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.
Working principle of U-shaped pressure 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 column "A" is exposed to atmospheric pressure, the pressure gauge actually shows the difference between the applied pressure and atmospheric pressure. Dealing with U-shaped pressure gauge, when measuring pressure, it is necessary to take into account the shift in levels in both columns.
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 meter It works well and the fluid used in it is of sufficient purity.
No circuits, no programs, no pressure gauge, yes
Having smoked a little on these topics: Digital pressure gauge
I realized that many car enthusiasts are not programmers or radio enthusiasts and not everyone will be able to assemble this digital pressure gauge. I propose a simpler digital pressure gauge that almost every car enthusiast can replicate
Since all of the above devices are based on voltage measurement. I decided to pair up a 24 V voltmeter I have, implemented on a MEGA48PA microcontroller, and a pressure sensor MM370 0-10 kg/cm2 with a resistance of 195 Ohms. Since we have an upper limit of the sensor of 10 kg/cm2, I applied a voltage of 10V to a voltmeter and measured the voltage at the input of MEGA48PA 28 leg; it was 0.5 Volt; therefore, the measurement limit of 0-10 kg/cm2 will correspond to 0-0 at the input of the ADC (28 leg), 5V.
Since the resistance of the sensor decreases with increasing pressure from 195 Ohm to 0 Ohm, it is necessary to alter it slightly so that the resistance increases with increasing pressure from 0 Ohm to 195 Ohm.
Conversion of the MM370 sensor for a digital pressure gauge.
Before remaking the sensor, its diagram can be drawn as follows (resistance decreases with increasing pressure) 
we need to redo it so that the circuit looks like this (increasing resistance with increasing pressure) 
To do this, you need to flare the sensor; I used side cutters.
Before this, you need to put marks on the cover and body of the sensor (later it will be useful during assembly). After disassembly, we see what is inside, namely the measuring element itself and the moving contact. Using a screwdriver, unscrew and remove the measuring element,
it needs to be turned 180 degrees, before doing this, cutting the contact a little (so that it doesn’t reach the body for me) 
Test measurements were made, and a graph was drawn up of the dependence of the MM370 resistance on the pressure gauge readings
and built a graph (almost linear)
My MM370(BU) also had a damaged wire,
connecting the moving contact to the body, I replaced it with wiring from a telephone headset.
We assemble and carefully roll (without using a hammer), you can fix it a little by welding (semi-automatic)
DEVELOPMENT OF THE VOLTMETER
To do this, you need to replace the 28 volt divider (in my case) in the input circuits of the voltmeter
Since we need a voltage limit from 0 to 0.5V, we use a 5V reference voltage source which is located in the voltmeter itself (power supply for the MEGA48PA microcontroller 4 pins). Using simple calculations, we need a divider by 10, since the resistance of the MM370 pressure sensor is 195 Ohms, then the resistance for the divider you need 1.95 kOhm, it’s better to put two, one of which is variable, I put two at 1 Kohm
Now we have three wires on the voltmeter plus + minus - power supply and pressure measurement.
We connect the pressure gauge to the compressor, do the calibration with a variable resistor (for more accurate readings, calibration must be carried out at the pressure at which we expect to use it)
They withstood the blow of the elements at the Sayano-Shushenskaya hydroelectric power station. They work on submarines and in mines. They are not affected by tropical humidity and arctic cold. They are real Tomsk pressure gauges.
The former Tomsk Pressure Gauge Plant, and now the Manotom company, managed to provide almost half the world with its instruments. 70 years of experience combined with modernization material base and the team retained at the enterprise allows you to practically work miracles.
The plant produces 500 thousand devices per year. Together with all modifications, the production range includes 10 thousand items. All this is supplied to almost 10 thousand consumers from different areas– from shipbuilding to nuclear power plants.
What is the production of pressure gauges like today?
The first step is development
It all starts when the company receives an order. The first to get involved are the design department employees. They determine what the device should be. If necessary, additional design equipment is ordered, which is produced here in the tool shop. As soon as the designers create an image of the future device, they get involved production workshops. It is not so rare to develop new modifications of devices - consumers ask for something new all the time.
Parallel production: from body to spring
From the designers, the development goes into the main production cycle, where 700 people work and the equipment fleet is 527 units. The technologies used here, by the way, were developed within the factory walls.
Once the design enters the main production cycle, case manufacturers come into play. Each type of pressure gauges and pressure sensors requires its own housing. If the device will be used in not too harsh conditions, the housing can be made of plastic or aluminum. If the pressure gauge is made for the military, or will be used in a “harsh” environment, then the case will be steel. IN different cases, the device body enters the mechanical or galvanic processing workshop. There is also a cold stamping workshop.
In parallel with this, the “insides” of the device are being assembled in other workshops.
The next step is painting the body. Here, too, there was some know-how. “We have introduced the most advanced powder coating technology to date,” says Deputy General Director for Production Andrey Metalnikov. — The bottom line is that conventional painting from a spray bottle with paint using the spray method is too expensive. Too much of it simply dissolves in the air without getting onto the product. With powder coating, 100% of the paint is used, because what does not end up on the product is returned to the drum and is not lost. In addition, the coating is more durable and durable.”
A special place in the list of divisions of the plant is the flexible springs section. This is where the heart of any pressure gauge is made. The reliability and accuracy of the pressure gauge depends on the quality of the flexible spring, its technical specifications. For Manotomi, Ural metallurgists developed a special alloy from which the springs are made.
The soldering section is the next step. Depending on the need, either soft or hard soldering device, and if necessary, then welding, including argon-arc.
A separate direction is the plastic products workshop. Thanks to modern thermoplastic equipment, parts from polypropylene, polystyrene and any other plastics can be produced here.
Naturally, Manotom cannot make the production cycle completely autonomous. For example, the plant receives glass parts and rolled metal from trusted suppliers. But, whenever possible, the plant tries to produce everything necessary in its own workshops. By the way, here they work only with Russian materials, imported parts are not used.
Those pressure gauges that require case strengthening, being almost ready, are sent to the galvanizing shop. Its presence is a feature of the Tomsk plant, because few enterprises can afford to maintain a galvanic shop. This is a very expensive production - and necessary equipment, and by its very essence. After all, electroplating involves various chemicals and acids that need to be disposed of after technological processes. And here they not only maintain such a workshop, but also constantly improve process in it.
The most important element of pressure gauge production is the workshop in which the transmission mechanism is created. The transmission mechanism is the central element of the pressure gauge, no less important than the spring. The more accurately and finely the transmission mechanism works, the more accurate the readings of the device. Therefore, the most experienced workers work in the production of transmission mechanisms, and technological equipment The workshop meets the most stringent modern requirements.
“We installed the latest equipment in mid-2010. This gave several tangible advantages at once. Firstly, the processing accuracy of transmission mechanism parts has increased. We managed to eliminate roughness and increase the accuracy of readings of our products. Secondly, thanks to this we were able to raise warranty period the work of our pressure gauges has doubled from one and a half years to three,” explained Andrey Metalnikov. Other suppliers of the Russian pressure gauge market still provide a one and a half year warranty.
The final stage of production is the assembly line. There are four main conveyors. Each serves its own area: technical instruments, thermometers, special instruments and electrical contact devices. Here the devices are assembled and undergo final quality control.
Before handing over products, each workshop must check it for compliance with the requirements. Department technical control The factory puts a stamp on the product and the process of creating a pressure gauge is completed.
IN recent years"Manotom" is developing the direction service their products. Thus, customers from nearby regions can send a broken product to the factory, where specialists will take care of it. In more remote areas and outside Russia, the plant enters into contracts for the maintenance of its pressure gauges with contractors.
Another new direction in work is the production of so-called “smart” electronic pressure gauges. They not only provide data, but also participate in the process of managing production facilities, replacing the human operator. So far, their share is not so large - only 15-20%. But the production volume of such pressure gauges is growing all the time.
“Today our devices float not only on all civilian ships, but also on all military ships, fly in missiles, and serve artillery. Supplies go to the CIS countries, Europe, Asia and Africa,” notes Andrey Metalnikov.
By tradition, a short video about how pressure gauges are made:
