Knowledge of using tension and pressure sensors

Knowledge of using tension and pressure sensors

In the entire application process of weighing sensors, the appropriate use of the manual has a closely related association with improving the effectiveness and efficiency of the sensor. To achieve the appropriate application of the sensor, it is necessary to have an appropriate grasp of the following aspects of the sensor as much as possible during application. 

 1. Packaged Pressure Sensor Basics

The packaged pressure sensor, put simply, is for the precise and accurate measurement of working pressure and has high sensitivity to working pressure. Different packaging types will cause different stress damages to the sensor, and different stress levels of different specification models will lead to different drift characteristics of the sensor. 

Sensor construction mainly includes the following three types: isolation diaphragm pressure sensor, TO packaged pressure sensor, and plastic - encapsulated pressure sensor electronic components. 

 1.1 Isolation Diaphragm Pressure Sensor 

The isolation diaphragm filling core body of the SENSYM/ICT19/13 series products is a kind of OEM pressure sensor that is most widely used in the world. Its inspection range is wide (5KPa ~ 100MPa), and it can accurately and precisely measure many types of compounds. It saves a lot of time and effort for consumers. As an OEM product, its various repackaging types greatly save time and effort for customers to produce and manufacture various working pressure interfaces. 

How to repackage is an effective packaging type. Here, an analysis is carried out for the following three packaging types. 

 Server Port Plan View Design of the Sealed Packaging Type (see Figure 1) 

This sealing method is to develop a pulse damper welded ring at the front end of the sensor, place an elastic material O - ring on the thread, and use the rear clamping ring to press the sensor tightly on the O - ring to achieve a sealing effect. This packaging type has significant limitations. Because the clamping ring exerts a strong working pressure on the sensor, causing it to receive a lot of stress, and it is very complicated to completely release the stress. Therefore, this repackaging type is not strongly recommended for customers to apply. If it must be used, try to apply it within the inspection range exceeding 300psi. When using this packaging type to test various indicator values of the sensor, it is generally not easy to obtain the manufacturer's approval. 

1.1.1 Side - sealed Packaging Type (see Figure 2) 

This sealing method is to place an elastic material O - ring in the southeast area of the sensor side, and use the deformation of the O - ring on the inner wall of the packaging cover to achieve a sealing effect. This packaging type has significant advantages. Because the deformation of the O - ring on the inner wall of the packaging cover has a good operation, so that the stress released on the sensor is not large enough to be ignored, and the sensor has a slight movement space on the axial direction of the inner wall, and there is no stress released on the sensor. Therefore, this installation method is also called a self - aligning installation method type. Its advantage is that the isolation diaphragm has a slight axial and radial free movement to ensure that the stress of the equipment is not transmitted to the diaphragm due to the misalignment of the assembly flow line. This installation method is very suitable for the inspection range of the isolation diaphragm pressure sensor. Everyone strongly recommends that customers apply this sensor packaging type. 

Figure 3 is the inner wall dimension diagram of the packaging cover of the SENSYM/ICT 19/13 series product sensors. The diameter models and specifications of the installation bases of the 19/13 series products are respectively: ∅19 + 0.08 + 0.04 and ∅12.7 + 0.03 + 0.00. Here, a 258 R rounded corner is designed on the top of the two holes. When assembling the flow line core body, apply an appropriate insulating oil on the O - ring of the core body, and then it will be very easy to push the core body to the edge of the base. 

In addition, the following 5 items should be noted when packaging the pressure sensor: 

1. When installing the core body, it should be noted that the pulse damper of the core body cannot be touched to prevent errors in the technical parameters of the sensor and the failure of the sensor. 

2. Do not extrude the ceramic pcbpcbpcb circuit board on the processed core body, or fill the cover with chemical substances that expand in volume due to external conditions (such as temperature), so as to prevent the damage of the ceramic thick film switching power supply principle. 

3. Do not keep tightening the power cord and pins of the core body to the cover, and do not pull hard to prevent the sensor pins from cracking or loosening. 

4. When pushing the sensor into the base for installation, if it is difficult to push or cannot be pushed, stop first. Forced pushing is not allowed to prevent damage to the sensor. 

5. The core body should be protected from collision, falling, and knocking. 

1.1.2 Welding Packaging Type (see Figure 4) 

With the development direction and popularization of sensor production line equipment, more and more manufacturers choose the welding method to package the isolation diaphragm pressure sensor. Due to the integrated circuit process, the temperature of the welded concrete components generally does not need to exceed 125°C, and the maximum operation is within 150°C, which increases the requirements for industrial equipment. The automatic welding machines that can generally be used for sensor repackaging include (special type) sub - arc welding machines, laser welding machines, and electronic beam welding machines. They can control the temperature of the welded concrete components within the required range. This packaging method greatly increases the types of usable compounds for the sensor and reduces the probability of leakage. However, it has very high requirements for the welding material stainless steel plate. When the quality of the stainless steel plate is low, it will damage the welding quality, reduce the compressive strength of the weld, and cause leakage at the working pressure pipe orifice. 

1.2 TO Packaged Pressure Sensor 

The TO - type packaged sensor is a simple electronic component that is relatively sensitive to working pressure. Its sensor is integrated on a chip with a layer of silicone gel exposed outside, stuck on the TO - 8 tube socket and surrounded by a composite material air guide cap. Its maximum working pressure inspection range is 150psi. Its packaging types can be divided into the following two types: 

1.2.1 Direct - insert Packaging Type 

It is the printed circuit board installation method. The air connection can be done by inserting a plastic hose, and for a larger inspection range, a polyester card can be used to clamp the plastic hose to ensure the effectiveness of the sensor working pressure connection. 

1.2.2 O - Ring Sealed Type 

Figure 5 is the plan view design of this sealing method. This sealing method is similar to Figure 1 in some aspects, but there is a significant difference in the introduced stress. The stress of the TO - packaged sensor when using this packaging can be ignored. 

1.3 Plastic - Encapsulated Pressure Sensor 

The plastic - encapsulated pressure sensors of SENSYM/ICT can be representatively divided into the following four types: P - packaged pressure sensor, A2 - packaged pressure sensor, N - type packaged pressure sensor, and D4 - type packaged pressure sensor. The actual packaging methods can be obtained with slight changes from the packaging methods of the following two types of products. 

1.4 Summary 

1.4.1 

When customers repackage the sensor, they should consider the original packaging type of the sensor. Under the standard of fully considering its working pressure inspection range, the assembly line stress introduced should be as small as possible. 

1.4.2 

For the sensor at the pressure server port with a reference working pressure, attention should be paid not to seal it up during packaging. 

2 Volume Resistivity 

For piezoresistive pressure sensors, the detection of volume resistivity is very crucial for laboratory instruments. The detection standard for the volume resistivity of the sensor is 50V, and the minimum wire joint resistor is 100MΩ. Many consumers use a 100V or even 500V insulation tester to detect it. As a result, the sensor will be thermally broken down due to high output power, leading to the damage of the sensor. 

Note**: It is strictly prohibited to use an insulation tester with a voltage exceeding 50VDC to detect externally diffused piezoresistive pressure sensors. 

 3 Toroidal Transformer Excitation 

The power supply and distribution system toroidal transformers of the sensor are divided into DC regulated power supplies and constant voltage sources. Each type of product has the type of power supply and distribution system and the maximum power supply and distribution system value in the operation manual. If the type of power supply and distribution system of the sensor is misused during application, it will cause the sensitivity and temperature characteristics of the sensor to change beyond the maximum power supply and distribution system value, and improper application will lead to the failure of the sensor characteristics.