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.

negative pressure transducer

Ⅰ. Preparation work before installation of pressure transmitter

1. Check the equipment: Since the equipment is designed by different pressure transmitter suppliers and features various models, it is necessary to determine the transmitter corresponding to each tag number according to the range, design and installation mode, and the material required by the process medium.

2. Determine the installation position: A variety of pressure transmitters can be installed anywhere if they are waterproof and dustproof. However, considering the convenience of daily operation and maintenance, and to extend service life and ensure reliability, the installation position should meet the following requirements:

(1) There is enough working space around, and the distance from adjacent objects (in any direction) is more than 0.5m;

(2) There is no serious corrosive gas around;

(3) It is not exposed to the surrounding thermal radiation and direct sunlight;

(4) To prevent the interference caused by the vibration of transmitter and pressure conducting tube (capillary), the pressure transmitter should be installed in the place without vibration.

 

Ⅱ. Installation requirements of pressure transmitter

1. Installation requirements of pneumatic pressure transmitter

(1) The pressure transmitter should be installed on the vertical or horizontal pipeline without strong vibration.

(2) The surrounding environment should be free of impurities corrosive to carbon steel, copper and alloy.

(3) For the convenience of maintenance and zero adjustment, adequate space should be reserved on the top and sides of the equipment.

(4) The pressure transmitter should be installed near (generally no more than 5m) the site requiring pressure measurement as much as possible.

(5) When the measured pressure is zero after installation, the output pressure of pressure transmitter should be 20KPa, otherwise it should be adjusted.

(6) The air source used for pressure transmitter should be filtered and purified compressed air.

 

2. Installation requirements of electric pressure transmitter

(1) Installation requirements for measuring gas pressure

A. When measuring the gas pressure, the pressure-relief point of the pressure measuring pipeline must be selected at the upper half of the pipeline to prevent liquid accumulation in the pipeline.

B. Flush valve should be installed at the front of pressure transmitter to prevent liquid or dirt from entering the transmitter.

C. When installing the pressure transmitter on the pipe throttling device, the pressure measuring point must be located within the area where the vertical line and the horizontal line meet at a 45-degree angle.

(2) Installation requirements for measuring steam pressure

When measuring the steam pressure, the pressure measuring point must be located within the area where the vertical line and the horizontal line meet at a 45-degree angle. The gas collector should be installed at the highest point of the pressure measuring point and the gas should be discharged regularly to ensure the measurement accuracy of the transmitter.

(3) Installation requirements for measuring the pressure of corrosive medium

When measuring the pressure of corrosive medium, an isolation device should be installed in front of the pressure transmitter and space liquid should be injected into it.

cost effective pressure sensor

The static characteristic of the low differential pressure sensor refers to the relationship between input and output when the input quantity is in steady state or a slowly changing signal. On account of at this time the input quantity and output quantity are not related to time, so the relationship between them, that is, the static characteristic of the low differential pressure sensor can be an algebraic equation without time variables, or using the input quantity as the abscissa and the corresponding output quantity as the ordinate to describe the characteristic curve. The main parameters that characterize the static characteristics of the low differential pressure sensor are linearity, sensitivity, hysteresis, repeatability, drift, etc.

(1) Linearity:

Linearity refers to the degree to which the actual relationship curve between the output quantity and input quantity of the low differential pressure sensor deviates from the fitting straight line. It is defined as the ratio of the large deviation value between the actual characteristic curve and the fitting straight line to the full-scale output value within the full range.

(2) Sensitivity: 

Sensitivity is an important indicator of the static characteristics of a low differential pressure sensor. It is defined as the ratio of the increment of the output quantity to the increment of the corresponding input quantity that caused the former. And the sensitivity is represented by S.

(3) Hysteresis: 

The phenomenon that the input and output characteristic curves of the low differential pressure sensor do not coincide during the change of the input quantity from small to large (positive stroke) and from large to small (reverse stroke) is called hysteresis. For the input signals of the same size, the positive and reverse stroke output signals of the low differential pressure sensor are not equal, and this difference is exactly called the hysteresis difference.

(4) Repeatability:

Repeatability refers to the degree of inconsistency of the characteristic curve obtained when the input quantity of the low differential pressure sensor changes continuously for several times in the same direction within the full range.

(5) Drift:

The drift of the low differential pressure sensor refers to the phenomenon that output quantity of the differential pressure sensor changes with time when the input quantity is unchanged, which is called drift. There are two reasons for drift: one is the structural parameters of the low differential pressure sensor itself; the other one is the surrounding environment (such as temperature, humidity).

cost effective pressure transducer

In the process of using the low differential pressure sensor, various bad experiences may occur due to inattention to some details. Today some experience of using the low differential pressure sensor is summarized to share with you, hoping to help you solve problems quickly.

1. The low differential pressure sensor has a large deviation compared with the pointer pressure gauge.

The appearance of deviation is a normal phenomenon, just confirm the normal deviation range. Due to the small measuring range of the low differential pressure sensor, the sensing element will affect its output. The pressure sensitive part of the low differential pressure sensor should be axially perpendicular to the direction of gravity during installation and adjust the zero position of the low differential pressure sensor to the standard value after the installation and fixation.

 

2. When the pressure goes up, while the output of the low differential pressure sensor can not go up.

 

In this case, check whether the pressure interface is leaking or blocked firstly, if it is confirmed not, check the mode of connection and the power supply, if the power supply is normal, simply pressurize to see whether the output changes or check whether the sensor zero position has output if there is no change, the sensor is damaged, which may be a problem caused by the instrument damage or other links of the entire system.

3. The output signal of the low differential pressure sensor is unstable

This failure may be a problem with the pressure source. The pressure source itself is an unstable pressure, which is most likely due to the weak anti-interference ability of the instrument or low differential pressure sensor, and the severe vibration of the sensor itself as well as the sensor failure.

electrical pressure transducer

The low differential pressure sensor divides the pressure into two types: positive pressure and negative pressure. The former is used for protective isolation, and the latter is used for isolation and control of infectious diseases transmitted through the air. For example, hospital wards, operating rooms, pharmacies, clean rooms for pharmaceuticals and semiconductor production, life science laboratories, and animal and botanical gardens use positive pressure protection, while the hospital wards for tuberculosis, measles, chickenpox, or SARS patients and biosafety laboratories are isolated by negative pressure to form a protective space for the public.

The low differential pressure sensor, also called negative pressure sensor / positive pressure sensor, is used to accurately measure the small pressure difference between the key area and the adjacent area (usually the adjacent corridor or lobby). These pressure gradients can prevent airborne infectious diseases or pollutants from spreading from the protected area to the contaminated area, and vice versa.

The critical medical environment has the characteristics of extremely low differential pressure measurement, with a full scale of 25Pa (0.0036 PSI). With the increasing importance of building energy consumption, the environmental differential pressure requirements are continuously decreased under the premise of ensuring safety.

electrical pressure transducer

There are intensive equipment in data center, where the heat is concentrated,at the same time, these precision equipment have high requirements for the temperature, humidity and cleanliness of the environment, therefore, it is necessary to have a reasonable airflow organization and distribution to effectively remove the heat in the machine room, so as to ensure that the machine room meet the environmental requirements of equipment such as temperature, humidity, cleanliness and air supply speed.

The low differential pressure sensor is mainly used to monitor the pressure difference between the two ends of the filter in the air conditioning system, participating in the variable air volume control system (VAVBox) and monitoring the pressure difference between the machine room, other rooms and corridors.

The filter in the air conditioning system is used to filter dust and impurities in the ventilation duct. As time accumulates, the dust on the filter will accumulate, which will gradually affect the air circulation of the filter. Due to poor air circulation, the pressure difference between the two ends of the filter increases continuously. The differential pressure transducer detects the pressure change, and the upper computer receives the signal from the low differential pressure sensor, when the signal value reaches the alarm point, it will start an alarm to remind of replacing or cleaning the filter.

The VAV controller adjusts the air supply volume and the temperature within the set range according to the actual temperature detected by the temperature sensor and the difference with the set temperature, the low differential pressure sensor detects the pressure change in the air duct to determine the air supply volume.

In order to ensure the air quality in the computer room, the primary room should maintain positive pressure. The pressure difference between the primary room, other rooms, and corridors should not be less than 5Pa, and the static pressure difference between the primary room and the outdoor should not be less than 10Pa. Using the low differential pressure sensor to monitor it can prevent the infiltration of outdoor air from destroying the environmental parameters in the machine room.

pressure sensor material

The low differential pressure sensor is generally divided into three categories: piezoresistive sensor, capacitive transducer and microelectromechanical (MEMS) sensor.

1. Piezoresistive sensor

Piezoresistive sensor is usually made of silicon and is bonded to a steel substrate by the adhesive effect between metals. When pressure is applied, this single-crystal diaphragm will deform, so that the resistance in the Wheatstone bridge will detect the pressure and then output the voltage proportionally. Piezoresistive sensor has good resolution and bandwidth, which is suitable for the applications with insufficient budget.

But this type of sensor also has its limitations. It is very sensitive to temperature changes and tend to drift. What is worse, this type of sensor cannot provide a large enough area to induce pressure to produce effective diaphragm deformation. It is no doubt that the diaphragm can be made thinner, but this will reduce its strength and integrity as well as also increase the cost. When used for low pressure measurement, its measurement results are noisy and the long-term stability is poor. Therefore this type of sensor is more suitable for high pressure measurement.

2. Capacitive sensor

Capacitance-based pressure sensor has become the mainstream of pressure measurement applications. Compared with piezoresistive pressure sensor, capacitive type pressure transducer has higher pressure sensitivity and lower temperature sensitivity.

Other advantages also include: simple design, no need to use special materials, low energy consumption, high resolution and low cost.

The capacitive sensor consists of a compact housing and two insulated metal plates placed in parallel inside. One of the metal plates adopts a metal diaphragm, which can be slightly deformed under pressure, and the other one is an insulated stainless steel electrode. When a pressure difference is applied to the metal diaphragm, the metal diaphragm will be displaced relative to the fixed electrode, which will change the capacitance. The linear comparison circuit detects that the capacitance change generated is proportionally amplified and outputs a high-level voltage signal. The deformation of the metal diaphragm is extremely small, which is beneficial to reduce the hysteresis and repetitive errors as well as speed up the response.

3. Microelectromechanical (MEMS) sensor

MEMS (Microelectro Mechanical Systems) sensor is a common capacitive sensor. It etches actuators, mechanical parts and electronic devices on the silicon substrate by using microlithography technology, which can be manufactured in large quantities at low cost. In addition, its volume is constantly shrinking, and its diaphragm area has been reduced to 13mm².

However, this miniaturization trend also limits performance, such as insensitivity, inaccuracy and signal drift. Because it is made of brittle materials, MEMS sensor is prone to fracture under high stress and cannot withstand excessive force. The biggest limitation of capacitive MEMS sensors is that miniaturization limits its pressure sensitivity in high-pressure applications.