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Knowledge About Pressure Indicator

December 13, 2021/in News /by administrator

The pressure indicator refers to instruments used to measure gas and liquid pressure, usually divided into mechanical pressure indicator, electronic pressure indicator and mechatronic pressure indicator.

1. Electronic pressure indicator

The basic component of the electronic pressure indicator is the pressure sensor, which can convert the pressure measurement parameters into electronic signals. The advantages of the electronic pressure indicators are their excellent dynamic performance and low material stress, resulting in high load impedance and excellent long-term stability, as well as compact structure and compact shape.

2. Mechatronic pressure indicator

Mechatronic pressure indicator usually refers to a mechanical pressure indicator integrated with electronic components or parts. This kind of instrument can not only display the measured pressure on the machine, but also provide electrical signal or contain electrical switch function. Even if the power supply is cut off or the measurement signal is interfered, the measurement value can still be read on site.

By combining the mechanical pressure indicator with different signals and switches, a variety of mechatronic pressure indicator products can be obtained. In addition, the sensor does not have any mechanical contact during operation, good wear resistance, and will not have any impact on the pressure indicator. Therefore, the pressure indicator manufacturer prefers to produce this kind of indicator.

3. Mechanical pressure indicator

This type of pressure indicator is not only sturdy and durable, but also easy to operate, with a wide range of applications. The elastic pressure element of the indicator deforms when subjected to pressure. The measurement system consists of a diaphragm box, diaphragm seal or Bourdon tube and is available in copper alloys, alloy steels, and special materials suitable for special measuring condictions.

4. Diaphragm seal

Diaphragm seals can meet the pressure measurement application requirements under severe environmental conditions. As the pressure indicator manufacturer, Alpha Instruments can also provide customers with the most suitable solutions such as corrosive, high viscosity or fibrous media, super high temperature, hard to hit a measurement point, measurements with high sanitation requirements as well as toxic or polluting media, etc.

Structures, Main Problems and Performance Characteristics of Silicon Capacitive Pressure Sensor

December 6, 2021/in News /by administrator

Ⅰ. Structures of the capacitive pressure sensor

The capacitive pressure sensors are based on silicon materials, using capacitance changes to convert pressure into capacitance changes, and are made by MEMS technology.

Ⅱ. Main problems of the capacitive pressure sensor

Because its detection principle is to use capacitive pole pitch variation, however is itself nonlinear. In order to improve the nonlinearity, develop a more complex core structure, such as contact, variable area in series with variable pole pitch, and other structures. Another problem that needs to be solved for displacement sensors is the detection of weak capacitive signals.

Ⅲ. Performance&characteristics of the capacitive pressure sensor

1. Capacitive pressure sensors are low-cost, which are suitable for mass production

The capacitive pressure sensor is made by MEMS technology, and the chip size is 3mm×3mm. A 4-inch silicon wafer can produce hundreds of components. The product has good manufacturability, consistent performance, suitable for mass production and low-cost operation. The preparation process is compatible with the IC process, and the process equipment is no need to be as expensive & complicated as the process equipment of the silicon resonant sensor, nor no need to be made in a single piece like the metal diaphragm capacitive sensor, which ensures that the silicon capacitive sensor has a high cost-performance.

2. Good stability

A capacitive pressure sensor is a structural sensor, and it also is an industrial pressure sensor. In terms of the detection principle, the stability of the pressure sensor is better than that of the physical sensor. From the perspective of the structure design, the stability of this type of sensor is ensured The structural process adopts a fully hard-sealed solid-state process, silicon-glass-metal pressure tube adopts electrostatic sealing, which reduces the stress, hysteresis, and deterioration caused by rubber sealing; the capacitor is not sensitive to temperature, the temperature additional error is not big, and it does not need to complicate temperature compensation like a silicon piezoresistive device. Good stability is one of the main reasons why silicon capacitive sensors are more popular.

3. Advanced parameters

The capacitive pressure sensor itself has the characteristics of low power, high impedance, small electrostatic attraction, and small heating effect, and can be used for non-contact measurement. The comprehensive performance index of silicon capacitive sensors such as nonlinearity, overload, static pressure, reliability, etc. are better than silicon piezoresistive sensors, ceramic capacitive sensors, and metal diaphragm capacitive sensors. The performance is equivalent to the silicon resonant sensor, especially refer to the non-linear index pursued by the user. Generally, the non-linearity of the silicon capacitive sensor is better than 0.05% FS, and the yield is more than 60%.

What Are the Maintenance Methods of the Pressure Transmitter?

September 22, 2021/in News /by administrator

Pressure transmitters have been widely used in various working environments. Maybe everyone knows how to choose a pressure transmitter and how to use a pressure transmitter, but do you know how to maintain a pressure transmitter? What are the methods for daily maintenance of the pressure transmitter?

1. Itinerant inspection of pressure transmitter

Check the indication of the pressure transmitter, whether there is any abnormality, and see if it fluctuates within the specified range; for the pressure transmitter without on-site display, go to the control room to see its secondary indication. Whether there is debris around the meter or whether there is dust on the surface of the meter, it should be removed and cleaned in time.

2. Regular inspection of pressure transmitter

For some instruments that do not need to be checked every day, check regularly at intervals. Regular zero check. For the pressure transmitter used in the control system, no matter how short the inspection time is, it is still necessary to change the automatic control to manual control, so as not to affect the operation of the controlled equipment.

Alpha Instruments was established in 2005 in Massachusetts, USA. We specialize in the development and manufacture of low differential pressure sensors, which have been used in HVAC, critical environment, medical industry, semiconductor equipment and other fields.

Through our own R&D center, we can carry out basic research and can also use our unique technology to develop sensors. The design of our products is based on decades of experience applied to new ideas. Compared with other capacitive sensors, our extensively designed patented products can provide better long-term stability, higher sensitivity and higher pressure capacity. If you have any need, please feel free to consult.

Method and Wiring Skills of Reducing Error of Low Differential Pressure Sensor

September 19, 2021/in News /by administrator

The pressure sensor is a device that can sense the pressure signal and convert the pressure signal into a usable output electrical signal according to a certain rule. It is usually composed of pressure sensitive components and signal processing unit. According to different test pressure types, pressure sensors can be divided into gauge pressure sensors, low differential pressure sensors and absolute pressure sensors. However, there will be some errors in the use of sensors in measurement. Among them, there will be errors in the use of low differential pressure sensors. If there are errors, they will affect the measurement results, so we must reduce these errors when using the sensors. Here’s how to reduce the error when installing low differential pressure sensors.

When in use, the liquid pressure tube should avoid high points, and the gas pressure tube should avoid low points. This is the preparation work to be done in the layout, so that the error can be reduced.

To reduce the error, the two pressure guiding tubes should be kept at the same temperature. At the same time, the caliber should be as large as possible, and the pressure guiding tube should be as short as possible.

There must be no gas in the liquid guide tubes, and the level of the two guide tubes should be the same when the spacer is used.

When the pressure pipe is connected to the process pipeline upward, its slope cannot exceed 1/12. And it’s time to measure liquid vapor on it.

Finally, when the low differential pressure sensor is measuring gas, the pressure guide pipe we refer to shall be connected downward to the process pipeline, in which the required slope shall not be less than 1/12.

Therefore, there are many benefits to the correct installation of the low differential pressure sensor, which is also a skill that every worker must master. The installation is of vital importance to the staff, and it is also necessary to master the wiring method of the sensor. Now let’s talk about how the sensors are wired.

In fact, the wiring methods of various sensors are basically the same. Pressure sensors generally have a two-wire system, a three-wire system, a four-wire system, and some have a five-wire system.

The two-wire system of the pressure sensor is relatively simple. Generally, customers know how to connect it. One wire is connected to the positive pole of the power supply, and the other is the signal wire connected to the negative pole of the power supply through the instrument, which is the simplest method.

The three-wire system of the pressure sensor is based on the two-wire system with a line that is directly connected to the negative pole of the power supply, which is a bit more troublesome than the two-wire system.

The four-wire pressure sensor must be two power input terminals, and the other two are signal output terminals. Most of the four-wire system is voltage output instead of 4-20mA output. The 4-20mA one is called pressure transmitter, and most of them are made into two-wire system. The signal output of some pressure sensors is not amplified, and the full-scale output is only tens of millivolts, while some pressure sensors have an internal amplifier circuit, and the full-scale output is 0~2V. As for how to connect to the display instrument, it depends on the range of the instrument. If there is a gear suitable for the output signal, it can be measured directly, otherwise a signal adjustment circuit must be added.

The five-wire pressure sensor is not much different from the four-wire system, and there are fewer five-wire sensors on the market.

The Precautions for Choosing a Low Differential Pressure Sensor

September 12, 2021/in News /by administrator

Many people don’t know how to choose a low differential pressure sensor that is suitable for their needs. Today, the precautions when choosing a low differential pressure sensor will be shared with you . 1. How much accuracy does the low differential pressure sensor need The accuracy is determined by the effects of nonlinearity, […]

Alpha – a Professional Differential Pressure Sensor Supplier

September 5, 2021/in News /by administrator

Alpha Instruments Inc. is a professional differential pressure sensor supplier integrating R&D, production and sales. It has unique core technologies in core materials, structural design, processing technology, etc., and can provide various standardized and customized differential pressure sensor products. The performance of Alpha’s differential pressure sensor products is industry-leading. Its smallest measurement range can reach 0-10Pa; the highest measurement accuracy can reach 0.25-1; the highest overload resistance can reach 15Psi (100kPa). The company’s various performance indicators, product consistency, and long-term stability are all at the leading level in the industry. After years of development, Alpha’s products have been extensively verified in the market and enjoyed high market visibility and brand reputation.

According to reports, the micro-differential pressure sensor is mainly used to measure the small pressure difference and monitor the small pressure difference between the internal and external spaces. The smaller the pressure difference is, the more difficult it is to measure accurately, and the higher the accuracy requirements of the sensor will be. The sensor also has strict requirements on its anti-overload ability and long-term stability, which is a typical high-end industrial sensor. The downstream application fields of differential pressure sensors are relatively wide, including HVAC, environmental pollution control, semiconductor manufacturing, biopharmaceuticals, modern aquaculture, textile machinery, medical instruments and equipment, oven pressurization and furnace air pressure control, natural gas, gas pipe network monitoring, underground ventilation and power plant wind pressure monitoring and other fields. Due to the high technical threshold of products, the differential pressure sensor supplier is still dominated by foreign brands.

Alpha Instruments Inc. is positioned in the subdivision field of pressure sensors, which belongs to the differential pressure sensors. The company masters the core technology, uses the unique variable capacitor structure and manufactures high-end pressure sensors with excellent performance, corrosion resistance and long-term stability, in order to achieve long-term accurate and effective measurement of small differential pressure.

The Common Terms Used in the Model Selection of Low Differential Pressure Sensor

June 22, 2021/in News /by administrator

The pressure is one of the important parameters in industrial production. To ensure the normal operation of production, pressure must be monitored and controlled. The following are the terms commonly used in the model selection of the low differential pressure sensor:

1. Standard pressure

It refers to the magnitude expressed by taking the atmospheric pressure as the standard, the pressure greater than the atmospheric pressure is called positive pressure, while the pressure less than the atmospheric pressure is called negative pressure.

2. Absolute pressure

It refers to the magnitude of pressure expressed by taking the absolute vacuum as the standard.

3. Relative pressure

The magnitude of the pressure for the comparison object (standard pressure).

4. Atmospheric pressure

It refers to the atmospheric pressure. The standard atmospheric pressure (1atm) is equivalent to the pressure of a mercury column with a height of 760mm.

5. Vacuum

It refers to the pressure state below atmospheric pressure. 1Torr=1/760 atmospheric pressure (atm).

6. Detection pressure range

It refers to the adaptive pressure range of the low differential pressure sensor.

7. The pressure that can withstand

When the low differential pressure sensor returns to the detection pressure, its performance does not degrade under the pressure that can withstand.

8. Round-trip precision

At a certain temperature (23°C), when the pressure is increased or decreased, the pressure variation value at the operating point is obtained by dividing the pressure value of output reversal with the full-scale value of the detection pressure.

9. Precision

At a certain temperature (23°C), when zero pressure and rated pressure are applied, the value is obtained by dividing the deviation from the specified value of the output current (4mA, 20mA) with the full-scale value, the unit is expressed by %FS.

10. Linearity

The output of the simulated low differential pressure sensor varies linearly with the detection pressure, but it has a deviation compared with the ideal straight line. The value of this deviation expressed as a percentage of the full-scale value is called linearity.

11. Hysteresis

Use zero voltage and rated voltage to draw an ideal straight line between the output current (or voltage) value, find the difference between the current (or voltage) value and the ideal current (or voltage) value as the error, and then find the error value when the pressure rises and when it falls. The value obtained by dividing the maximum value of the absolute value of the above difference with the full-scale current (or voltage) value is the hysteresis. The unit is expressed by %FS.

The Main Application of Capacitive Pressure Sensor in Automobile Industry

June 15, 2021/in News /by administrator

A brief introduction of capacitive pressure sensor

The ceramic capacitive pressure sensor uses a ceramic diaphragm as a pressure-sensitive element. The ceramic diaphragm and the ceramic substrate are respectively made into the two poles of the capacitor. When external pressure acts on the ceramic diaphragm, the ceramic diaphragm is deformed and the distance between the two poles changes, resulting in a change in capacitance, and then through a specific ASIC conditioning chip to output a standard voltage signal.

The structrue of the Capacitive pressure sensor

Ceramic capacitive pressure sensor mainly consists of two parts: ceramic substrate and ceramic diaphragm in structure. The ceramic diaphragm and ceramic substrate are sintered together with high-temperature molten glass to play a sealing role. Electrode patterns are printed on the inside of the ceramic substrate and the ceramic diaphragm to form a variable capacitor. When the measured external pressure is transmitted to the ceramic diaphragm through a special channel, the capacitance between the ceramic substrate and the ceramic diaphragm will change with the pressure, and then specific ASIC conditioning chip converts the measured capacitance signal into a voltage signal through a set conversion equation.

Ceramic capacitor technology has the advantages of moderate cost, good corrosion resistance, and strong media compatibility. Pressure sensors using ceramic capacitors as pressure-sensitive components are widely used in pressure detection of water, gas, and liquid media. It is especially suitable for the harsh working environment of automobile systems, for air-conditioning pressure, air brake pressure, oil pressure, exhaust back pressure and transmission pressure.

Four Common Faults of Pressure Transducer and Anti-interference Measures

June 8, 2021/in News /by administrator

Ⅰ. Four common faults of pressure transducers

The first fault is that when the pressure goes up, the pressure transmitter output cannot go up. In this case, check whether the pressure port is leaking or blocked first. If not, check the wiring method and the power supply. If the power supply is normal, simply pressurize it to see whether the output changes, or check whether the zero position of the sensor has output. If there is no change, the sensor has been damaged, possibly due to instrument damage or other problems in the whole system.

The second is in the first pressurization, the output of the pressure transmitter does not change, and the output of the transmitter changes suddenly after the pressure is released, and the zero position of the pressure transmitter cannot return after the pressure is relieved. It is very likely that the pressure sensor sealing ring has problem. Commonly, due to its specifications, the sealing ring is compressed into the pressure port of the sensor to block the sensor after it is tightened. When pressurized, the pressure medium can’t enter, but when the pressure is high, the sealing ring is suddenly burst open, and the pressure transducer is changed by the pressure. The best way to eliminate this fault is to remove the pressure transducer and directly check whether the zero position is normal. If the zero position is normal, you can replace the sealing ring and try again.

The third fault is the unstable output signal of the pressure transmitter. This fault may be a source of stress. The pressure source itself is an unstable pressure. It is very likely that the anti-interference ability of the instrument or pressure transducer is not strong, the vibrating of pressure transducer or the pressure transducer is faulty.

The fourth fault is the large deviation between the transmitter and the pointer pressure gauge. Deviation is normal, just confirm the normal deviation range.

The final type of fault is the effect of the position of the low differential pressure transmitter on the zero output. Due to its small measurement range, the sensing element will affect the output of low differential pressure transmitter. During installation, the pressure sensing part of the transmitter should be axial perpendicular to the direction of gravity. After installation and fixing, adjust the zero position of the pressure transmitter to the standard value.

Ⅱ. Anti-interference measures for pressure transducer

1. Maintain stability

Most pressure transducer will be unstable after overtime work, so it’s important to know how stable the pressure transducer is before you buy it. This advance work can reduce the trouble of future use.

2. Packaging of pressure transducer

The packaging of the pressure transducer, especially the frame, is often easy to ignore, but its shortcomings will gradually be exposed in the future use. When purchasing a pressure transmitter, you must consider the working environment of the pressure transducer in the future, how the humidity is, how to install, whether there will be strong impact or vibration, etc.

3. Select the output signal

What kind of output signal the pressure transducer needs: mV, V, mA, frequency output, and digital output, depends on many factors, including the distance between the sensor and the system controller or display, whether there is “noise” or other electronic interference signals, whether the amplifier is needed, and the location of the amplifier. For many devices with a short distance between the pressure transducer and the controller, the pressure transducer with mA output is the most economical and effective solution. If the output signal needs to be amplified, it is best to use a sensor with built-in amplification. For long-distance transmission or strong electronic interference signals, it is best to use mA output or frequency output.

An Overview of Negative Pressure Isolation Room

June 1, 2021/in News /by administrator

The main purpose of the negative pressure isolation room is to separate the patient from the surrounding environment and people, avoid direct contact with the body or air exchange, and prevent cross-infection.

The main building of the negative pressure isolation room must reach the airtight level, and the gap between the electromechanical system and the structure must be carefully handled through the room. Airtight ceilings are generally installed in negative pressure isolation rooms to provide airtight protection. During maintenance, if the ceiling is opened, the effectiveness of the air tightness may be reduced, and the air tightness test must be performed again according to the American ASTM E779-1 standard, because the airtightness of the negative pressure isolation room is extremely important.

Since the air pressure of the negative pressure isolation room is lower than the outside world, only fresh air from outside can flow into the ward, and the air contaminated by the patient in the ward will not leak out directly, then will be discharged to the waste through a special pipeline in time processing equipment. It can be said that the negative pressure isolation room is like a space completely isolated by a “mask”, and the place outside the ward will not be contaminated at all, so that medical staff can safely carry out activities outside the ward, reducing the possibility of a large number of infections. This kind of ward is most suitable for treating patients with respiratory infections like SARS.

The negative pressure isolation room is not just a room, but is composed of three parts: a ward, a buffer room, and a bathroom. The pressure difference in each room is -5Pa from the inside to the outside.

Some people may worry that if the room is under negative pressure, will the patient have difficulty breathing? Of course not. Although the pressure is lower than the outside world, it is only 15Pa less. The atmospheric pressure on the ground is generally around 100KPa, and changes in tens of Pa will not affect the patient’s breathing at all. On the contrary, through the careful care of the fresh air system, the patient can better recover the body and get rid of the disease.

In order to keep the various ventilation equipment in the ward running normally, a micro-pressure gauge should be installed in the ward, buffer zone, and bathroom door, and a dedicated person should record it regularly to ensure that the indoor pressure difference fails.