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How to select monocrystalline silicon/diffused silicon pressure transmitter, the cause of failure and the solution

Release time:2023-02-14Click:62

According to the core, the pressure transmitter can be divided into diffused silicon pressure transmitter, ceramic pressure transmitter, capacitive pressure transmitter and monocrystal silicon pressure transmitter. Do you know what type of pressure transmitter is used most often to measure pressure?

That's the diffused silicon pressure transmitter. Diffused silicon pressure transmitter is widely used in petroleum, chemical, steel, electric power, light industry, environmental protection and other industrial fields, to achieve a variety of fluid pressure gauge, negative pressure or absolute pressure measurement and control, and can be applied to a variety of harsh dangerous environment and corrosive media. So how did the diffused silicon pressure transmitter come about?

Birth of diffused silicon pressure transmitter

In the mid-1990s, Nova produced a new type of diffused silicon pressure sensor with two cutting-edge technologies, siliconite and silica-chip, and developed a diffused silicon pressure transmitter with high precision, low repeatability and corrosion resistance. The process pressure is transmitted to the diffused silicon diaphragm through the isolation diaphragm and sealed silicone oil. At the same time, the pressure at the reference end (atmospheric pressure) acts on the other end of the diaphragm. This pressure difference between the two sides of the diaphragm creates a pressure field that compresses part of the diaphragm. In the other part of stretching, there are two strain resistors in the compression region and the tension region respectively to feel the change of resistance value caused by pressure, so as to convert the pressure signal into an electrical signal.

Selection of diffused silicon pressure transmitter

All right, back to business! Xiaobian today will introduce the selection of diffused silicon pressure transmitter. The selection of small series summed up, there are eight parameters.

01 Medium to be measured

The physical and chemical properties and states of the measured medium, such as strong acid, strong alkali, viscous, easy solidification crystallization and gasification conditions. General diffused silicon pressure transmitter pressure, oil pressure, hydraulic pressure can be measured, but because the diffused silicon core is 316l core, can not be measured for the corrosion of stainless steel gas, viscous media and easy to crystallize media. Because the viscous and crystalline material is easy to block the pressure hole, resulting in the core can not contact the medium.

Crystallizing and viscous media need to be measured with a flat film pressure transmitter. Conventional pressure transmitters are easy to be blocked because they have pressure holes, so they need to use a flat film pressure transmitter. The flat-film pressure transmitter ensures that the medium is in direct contact with the diaphragm. Flat film pressure transmitter is generally used in the food and pharmaceutical industries (installation mode is generally clamp installation, the pressure should not exceed 4MPa, or the clamp installation is not easy)

ps: Do not scratch the diaphragm with your hand, it is easy to damage the diaphragm!

Mud and asphalt these need no cavity flat film pressure transmitter (pressure needs to be greater than 2MPa can be measured)

02 Pressure range

The range of diffused silicon pressure transmitter is generally -0.1mpa - 60MPa, according to the actual pressure to choose, generally more than the maximum pressure on the site. But there are many units of pressure, such as: a customer asked, 16 kilograms of pressure is how much?

Don't be nervous! Remember the small formula to handle different pressure units: 1MPa=10bar=1000KPa=145psi=760mmHg=100 meters of water column.

So don't panic when you hear 16 kilograms of pressure, 10 meters high water column, please remember the small formula. Please note: Gauge pressure and absolute pressure when the customer gives the pressure range. Gauge pressure is zero for standard atmosphere, and absolute pressure is zero for vacuum. So the question is, what should you pay attention to when choosing a pressure transmitter at high altitude? Zero atmospheric pressure is different. Large range is negligible (above 1.6MPa). The answer is: please choose a pressure transmitter whose process is gauge pressure (with a conduit that will direct zero to the atmosphere) to prevent error caused by zero. The conventional process is sealed gauge pressure - sealing a standard atmospheric pressure into the zero, so pay attention to the selection, measurement of more than 10MPa pressure is not necessary, so small pressure is not enough to affect the accuracy.

03 Temperature

The temperature resistance of the diffused silicon pressure core is -20-80℃, so the temperature of the medium to be measured cannot be too high. If you need to measure the medium above 80℃ or even about 300℃, how do you need to do?

1, choose to add heat sink, bring down the temperature

2, the selection of pressure tube, can also achieve the effect of medium cooling

04 Power Supply

The sensor power supply is usually DC24V, which is generally wide range on the market now. The lowest power supply is generally 5V, no matter how small.

05 Output signal

4-20mA two-wire current signal 1-5V, 0-5V, 0-10V three-wire voltage signal RS485 signal

06 Specifications of the screw threads

Commonly used threads are M20*1.5, G1/2, G1/4, M14*1.5

07 precision class

Commonly used accuracy levels are 0.5%, 0.3%.

Do not recommend 0.1% precision oh, diffusion silicon pressure transmitter 0.1% precision is not stable enough, so if you need high precision can recommend monocrystalline silicon.

08 Connection Mode

1> Hersman connector 2> Aviation plug 3> direct lead

Three kinds of wiring have advantages and disadvantages, to see the specific site selection, generally is the most used by Hersman. Hersman joint has better protection; Aviation plug is easy to replace, easy to connect; Direct lead size is small, easy to install. In addition if you need to bring the display is also OK. Ps: Please note that the diffused silicon pressure transmitter with display can only do 4-20Ma output outdoor with optional 2088 housing

In addition, different types of selection will be carried out in different situations. A few more questions, let's see who can answer them:

1 > What special process is needed to measure ammonia gas?

2 > Measure flammable and explosive gas need to diffusion silicon oil into what?

Six characteristics of monocrystalline silicon pressure transmitter

1, fully sealed, fully isolated monocrystalline silicon pressure sensor, precise liquid filling technology, eliminate the influence of temperature, static pressure, double diaphragm overload structure, calmly cope with high overload test.

2, ASIC and surface packaging technology signal transmission module, powerful 24-bit ADC to achieve high precision and fast response, display module can rotate 360°, button parameter operation function friendly.

3, super transient voltage protection terminal module, strong personal protection, transmitter security guard, even after lightning and thunder, still maintain stable work.

4, high strength metal electrical protection shell, beautiful appearance, fully show the beauty of fashion technology, solid inner, meet the most demanding environment.

5, the external button menu function to achieve field operation, fully isolated magnetic induction structure, meet the requirements of flameproof field safety operation specifications, key parameters do not affect the electrical protection level, safer and faster.

6, solid high quality stainless steel process flange, super thick reinforced structure, indestructible, high static pressure, high overload strong guarantee.

What if the diffused silicon pressure transmitter fails? Here's a look at the reasons and solutions:

1. When installing, the pressure sensitive part of the diffused silicon pressure transmitter should be vertically perpendicular to the direction of gravity. If limited by installation conditions, the diffused silicon pressure transmitter should be adjusted to the standard value after fixed installation.

2. The remaining pressure can not be released, so the zero position of the sensor can not come down. The best way to eliminate this reason is to remove the sensor and directly check whether the zero position is normal. If the zero position is normal, replace the sealing ring and try again.

3. The output of the pressure diffused silicon pressure transmitter does not change, and then the output of the pressure diffused silicon pressure transmitter suddenly changes, and the zero position of the pressure relief diffused silicon pressure transmitter does not go back. The reason for this phenomenon is very likely to be caused by the pressure sensor seal ring.

4. Whether it meets the requirements of power supply; Whether there is any wiring error between the power supply and the diffused silicon pressure transmitter and the load equipment. If there is no voltage at the terminal of the diffused silicon pressure transmitter or the polarity is reversed, the diffused silicon pressure transmitter will have no voltage signal output.

5. The shell of the pressure sensor and diffused silicon pressure transmitter generally needs to be grounded, and the signal cable shall not be mixed with the power cable. Strong electromagnetic interference should be avoided around the sensor and diffused silicon pressure transmitter. Sensors and diffused silicon pressure transmitters should be periodically verified in accordance with industry regulations.

6. When choosing pressure sensor and diffused silicon pressure transmitter, the user should fully understand the working condition of the pressure measuring system and make reasonable selection according to the needs, so that the system can work in the best state and reduce the project cost.

7. The filling liquid in the isolation plate and element is transmitted to both sides of the measuring diaphragm. The measuring diaphragm and the electrodes on both sides of the insulation plate form a capacitor.

8, the pressure diffusion silicon pressure transmitter requires a weekly check, check once a month, mainly to remove the dust in the instrument, check the electrical components carefully, the output current value should be often proofread, the pressure diffusion silicon pressure transmitter inside is weak current, must be separated from the outside strong electricity.