No circuits, no programs, no pressure gauge, yes
Having smoked a little on these topics: Digital pressure gauge
I realized that many of the car enthusiasts are not programmers or radio amateurs and assemble this digital pressure gauge Not everyone can. 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 MM370 0-10 kg/cm2 pressure sensor 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 doing 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, trimming 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, the calibration must be carried out at the pressure at which we expect to use it)
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.
...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.
They withstood the elements for Sayano-Shushenskaya HPP. They work for submarines and in the 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 a modernized material base and a retained team at the enterprise, allows us 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 various fields - 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, production workshops get involved. 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 the deputy general director produced by 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. At 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 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 of the device is performed, and if necessary, 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 technological process in him.
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 increase the warranty period of our pressure gauges from one and a half years to three at once - twice,” explained Andrey Metalnikov. Other suppliers Russian market The pressure gauges still come with a year and a half warranty.
The final stage of production is the assembly line. There are four main conveyors. Each serves its own area: technical instruments, thermometers, special devices 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 last years Manotom is developing the service area for its 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.
Traditionally short video about how pressure gauges are made:
