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.

surface mount pressure sensor

The low differential pressure sensor is powered by 5V with an output of 0.25-4V. Although it is the analog output, the internal linearization and temperature compensation are all realized digitally, ensuring high accuracy and resolution ratios (up to 0.05 Pa). It is thus unsusceptible to temperature.

The low differential pressure sensor has two specific output modes, including linear and square output which are completely interchangeable. Relying on simple peripheral circuits, such as 0-10V output or other interfaces, high-quality transmitters can be produced.

Its leading performance is based on the integration of sensing elements, signal amplification, and A/D conversion into the same silicon chip. The thermal sensor element measures differential pressure. Compared with other thermal differential pressure sensors, it requires less air and can work under the extremely harsh environment in a safe and reliable way. Compared with the diaphragm sensor, the low differential pressure sensor has a wider measuring range, more stable performance and more excellent renaturation in the section of low differential pressure. In addition, the low differential pressure sensor can withstand large instantaneous pressure and is not sensitive to the installation direction.

The low differential pressure sensor has the following characteristics:

1. Accuracy:

(1) Digital accuracy: ±0.05%

(2) Full performance: ±0.25F.S

2. Strong performance for pressure measurement, differential pressure measurement and flow measurement

3. Range ratio: 100:1

4. Stability: 0.25%, 60 months

5. Measurement rate: 0.2S

6. Stainless steel cover that is easy to install and ensures excellent cold and thermal stability

7. Process connections are compatible with other products for optimal measurement

8. Adoption of the intelligent transmitter with a 16-bit computer

9. Standard current output of 4-20mA, protection mechanism for mis-wiring, environmental design, and compliance with RoHS standard

electronic pressure transducer

When it comes to pressure transducer, perhaps we are most familiar with its application in medical devices, such as ventilators, electronic blood pressure monitors and other products. But in fact, pressure transducers are also one of the most used measuring devices in automatic control in the petrochemical industry. In large-scale chemical projects, almost all pressure transducer applications are included, such as differential pressure, absolute pressure, gauge pressure, high pressure, slight differential pressure, high temperature, low temperature, and remote flange pressure transducer of various materials and special processing. Almost the petrochemical industry’s demand for pressure sensors is mainly concentrated in three aspects: reliability, stability and high precision. Among them, reliability and many additional requirements, such as turndown ratio, bus type, depend on the transmitter’s structural design, mechanical processing level and structural materials. The stability and high accuracy of the pressure transmitter are mainly guaranteed by the stability and measurement accuracy of the pressure transducer.

The measurement accuracy of the pressure transmitter corresponds to the measurement accuracy and response speed of the pressure transducer, and the stability of the pressure transmitter corresponds to the temperature characteristic, static pressure characteristic and long-term stability of the pressure transducer. The demand for pressure transducer uses in the petrochemical industry is reflected in measurement accuracy, rapid response, temperature characteristics and static pressure characteristics, and long-term stability.

The material of pure monocrystalline silicon has low fatigue, and the pressure transducer made of this material has long-term stability. At the same time, the pressure transducer is easy to be integrated with the temperature sensor, which increases the temperature compensation accuracy and greatly improves the temperature characteristics and measurement accuracy of the sensor, which can well meet the demand for pressure transducer in the petrochemical industry.

Pressure is one of the most important parameters in industrial production. In order to ensure the normal operation of production, pressure must be monitored and controlled to achieve automatic control, safety monitoring and alarm functions. Pressure transducers are widely used in pressure switches and vacuum equipment, flow control, air conditioning system fan control, etc. Accurate measurement is a key requirement, and the ability to withstand harsh environments is also important. The transducers produced by Alpha Instruments have always enjoyed high reputation and are your best choice!

electronic pressure transducer

1. Calibration is needed by pressure transmitter

After being used for a while, the measurement performance of the pressure transmitter may be changed, and the phenomena of zero drift and increasing measurement error will appear. Therefore, it is necessary to carry out regular calibration of the pressure transmitter. The calibrator should be 3 times more accurate than the required calibration accuracy. Standard pressure values of 0%, 25%, 50%, 75%, and 100% are input successively into the transmitter via the pressure calibrator in a forward and reverse manner, to detect whether the output signal of the electric current is within the allowed accuracy range. If out of range, it needs to be calibrated.

 

2. Calibration methods of pressure transmitter

The calibration methods are as follows (4~20mA output):

(1) Input the standard pressure of 4mA with pressure calibrator and adjust the ZERO potentiometer to make sure that the electric current output falls within the accuracy range;

(2) Input the standard pressure of 20mA with pressure calibrator and adjust the SPAN potentiometer to make sure that the electric current output falls within the accuracy range;

(3) ZERO and SPAN potentiometers are mutually restrictive. Repeat step (1) and step (2) until both the current outputs of 4mA and 20mA meet the accuracy requirements, and then check whether the current outputs of 25%, 50%, and 75% meet the accuracy requirements. If so, it indicates the calibration of pressure transmitter produced by pressure transmitter manufacturer is qualified.

Alpha Instrument Inc. is specialized in the development and manufacturing of low differential pressure sensors, which have been used in heating ventilation air conditioning, critical environment, medical industry, semiconductor equipment, and other fields. Our innovatively designed products provide long-term stability, higher sensitivity, and higher overvoltage capacity. Welcome to contact us to buy!

cost effective pressure sensor

Ⅰ. Extensive research fields on the pressure transmitter

Nowadays, extensive researches on pressure transmitter are carried out around the world, diving into almost every industry.

 

Ⅱ. Development trend of pressure transmitter

1. Intelligence

Due to the emergence of intelligence technology, some microprocessors can be added to the integrated circuit, equipping the pressure transmitter with functions of automatic compensation, communication, self-diagnosis, logical judgment, etc.

2. Integration

More and more pressure transmitters have been integrated with other measurement transmitters to establish measurement and control systems. An integrated system can improve operation speed and efficiency in process control and factory automation.

3. Miniaturization

There is a growing demand for micro pressure transmitters as this kind of transmitter can work under extremely harsh environments, which requires few maintenance and produces small environmental affects.

4. Standardization

A series of standards about the design and manufacture of transmitters have been established.

5. Generalization

Another development trend of pressure transmitter lies in its expansion from the mechanical industry into other fields, such as automotive components, medical instruments, and energy and environment control systems.