high accuracy pressure transducer

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.

cost effective pressure sensor

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.

variable capacitance pressure sensor

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, […]

low pressure differential pressure transducer

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.

electrical pressure transducer

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.

capacitive pressure sensor

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.

low price pressure sensor

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.

cleanroom environmental monitoring

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.

intrinsically safe pressure transducer

The low differential pressure transmitter is a type of instrumentation equipment commonly used in modern industrial production, which can be called the “eye” of modern industrial production. In the production process, it can observe and control the pressure, flow, temperature, liquid level, and other measurement data of the entire production process. And then the data can be transferred to the logic algorithm in the central control system (DCS or PLC) through low DP data exchange. At the same time, adjustment is made by the regulator or control unit. Finally, the control of the production target values is completed. Thus, the low differential pressure transmitter is an important prerequisite for the establishment of a good control loop. Pressure transmitters and differential pressure transmitters are typical representatives of the “eye”, which are widely used due to their high precision and stability.

 

1. The classification of the low differential pressure transmitter 

The function of the low differential pressure transmitter, in simple terms, is to convert the displacement or force of the elastic load cell into a standard electrical signal. Based on the composition and working principle, it can be divided into force-balance transmitter and displacement transmitter while the latter is generally used in the glass production line. Based on the measurement accuracy and objective, it can be divided into the micro differential pressure transmitter, the differential pressure transmitter, and the pressure transmitter. And besides, according to the signal transmission and power supply mode, it can be divided into a two-wire transmitter and a four-wire transmitter.

 

2.  The application of the low differential pressure transmitter

Based on what we have learned, it is realized that the displacement transmitter is more approved by the market than the force-balance transmitter in today’s measurement field. The same is true in the design process of the glass production line. However, in terms of differences in measurement objectives and accuracy, there are still differences in the selection of the low differential pressure transmitter.

(1) The high-precision micro-differential pressure transmitter is used in the furnace to measure the pressure of the kiln, which is one of the fundamental safety and measurement objects. At this moment, the pressure pipe of P1 needs to go deep inside the furnace wall while the pressure of P2 is the atmospheric pressure at the temperature close to that of the furnace. The pressure pipe that is finally connected to the low differential pressure transmitter should be the average value of the pressure on both sides of the furnace. Next, based on the principle of the transmitter, the gauge pressure inside the furnace can be obtained through P1-P2.

(2) The low differential pressure transmitter and the orifice plate flowmeters throttling device can be used for the measurement of natural gas, hydrogen, oxygen, and combustion-supporting airflow. A disk with a central hole is inserted into the pipeline. When the fluid passes through the orifice plate, the cross-section of the flow beam is reduced, causing a local difference in flow velocity and a relatively significant pressure difference. The flow rate of the fluid is proportional to the square root of the pressure difference before and after the throttle element under certain conditions. In the formula, Q is the measured flow, F0 is the opening area of the orifice plate, α is the flow coefficient, ρ is the liquid density, P1 is the inlet pressure of the orifice plate and P2 is the outlet pressure of the orifice plate.

In addition to its important role in the key measurement areas in the glass production line, the low differential pressure transmitter has many derivative applications, such as the measurement of the height change of the glass liquid level and the liquid level height, etc, which will not be described in detail here.

 

3. The development of the low differential pressure transmitter

Compared with liquid, it is more complicated to measure gas flow due to its compressibility. The volumetric flow rate Q of the gas is a function of the differential pressure (P1-P2) and the density ρ while the density is a function of the current temperature and pressure of the gas. In the practical application, there will be a large measurement error due to the difference between the current density of the medium and the density during design. Therefore, temperature and pressure compensation should be performed on it.

In the past, designers install both thermal resistance and a pressure transmitter near the location where the gas pipeline is set up the flowmeter. All three groups of signals are entered into the DCS system, and the compensation calculation is completed with the formula in the computer system. However, this model is gradually being replaced nowadays. With the emergence of a new generation of multi-parameter intelligent transmitters, this type of transmitter comprehensively improves the accuracy, reliability, and long-term stability of the low differential pressure transmitter by using a microprocessor as a basis.

electronic pressure transducer

The intelligent or mechanized operation of all walks of life can’t be separated from the development of science and technology and machines, which also gradually reduces the load of manual labor, greatly improves the efficiency. Pressure transducer is the most common sensing instrument in industrial practice. It is widely used in various industrial automation environments, such as water conservancy and hydropower, intelligent buildings, aerospace, military, petrochemical and many other industries. However, because it is indirectly related to your daily life, you will not know much about it, so Alpha Instruments is going to talk about it in detail.

Pressure transducers can be divided into a variety of different types, such as heavy-duty type. It is usually used in transportation to maintain the performance of heavy-duty equipment mainly by monitoring the pneumatic, hydraulic, brake pressure and air brake and other key systems of pressure, flow, and liquid level. This pressure transducer has a housing, a metal pressure connection, and a setting device for a high-level signal output. It is cylindrical in appearance with a pressure connection at one end and a connector at the other. It can be used in extreme temperature and electromagnetic interference environment. Customers in the industrial and transportation fields can use the industrial pressure transducer in the control system to effectively monitor and feedback the pressure of cooling liquids, lubricating oil and other fluids. Once problems are found, timely measures can be taken to solve them.

The above is the main classification of pressure transducers and their application in the industrial field.