How to tension loadcell

A tension loadcellis a sensor used to measure the tension of liquids and gases. Similar to other sensors, the tension loadcellconverts tension into electrical signal output when it works.

 

What are different tension loadcell?

There are great differences in the technology, design, performance, working conditions and prices of tension loadcells used. It is roughly estimated that there are more than 60 kinds of tension loadcells in the world and at least 300 companies produce tension loadcells.

 

tension loadcells can be classified by the tension range they can measure, the operating temperature, and the type of tension; the most important of which is the type of tension. If classified according to the type of tension, tension loadcells can be divided into the following five categories:

 

①、Absolute tension load cell:

This kind of tension loadcellmeasures the real tension of the fluid, that is, the tension relative to the vacuum tension. The absolute atmospheric tension at sea level is 101.325kPa (14.7?PSI).

 

② gauge tension loadcell(gauge tension loadcell):

This kind of tension load cellcan measure the tension relative to the atmospheric tension at a specific location. The tire tension gauge is an example. When the tire tension gauge shows a reading of 0PSI, it means that the tension inside the tire is equal to the atmospheric tension, which is 14.7PSI.

 

③、Vacuum tension loadcell:

This kind of tension loadcellis used to measure the tension less than one atmosphere. The reading value of some vacuum tension loadcells in the industry is relative to one atmosphere (the reading value is negative), and some are based on the absolute tension.

 

④. Differential tension gauge:

This instrument is used to measure the tension difference between two tensions, such as measuring the tension difference between the two ends of the oil filter. The differential tension gauge is also used to measure the flow rate or measure the liquid level in the tension vessel.

 

⑤、Sealed tension loadcell:

This instrument is similar to a gauge tension loadcell, but this instrument is specially calibrated to measure the tension relative to sea level.

 

According to the difference in structure and principle, it can be divided into: strain type, piezoresistive type, capacitive type, piezoelectric type, vibration frequency tension loadcell, etc. In addition, there are photoelectric, optical fiber, ultrasonic tension loadcells and so on.

 

What is strain gauge tension loadcell?

 

A strain gauge tension loadcell is a sensor that indirectly measures tension by measuring the strain of various elastic elements. According to the different materials, strain elements can be divided into two categories: metals and semiconductors. The working principle of strain elements is based on the "strain effect" of conductors and semiconductors, that is, when the conductor and semiconductor materials undergo mechanical deformation, their resistance value will change.

 

When the wire is subjected to external force, its length and cross-sectional area will change, and its resistance value will change. If the wire is stretched by external force, its length will increase, while the cross-sectional area will decrease, and the resistance value will increase. big. When the wire is compressed by external force, the length decreases and the cross-section increases, and the resistance value decreases. As long as the change in the voltage applied across the resistor is measured, the strain of the strained wire can be obtained.

 

What is piezoresistive tension loadcell?

Piezoresistive tension loadcell refers to a sensor made by using the piezoresistive effect of single crystal silicon material and integrated circuit technology. After the single crystal silicon material is subjected to the force, the resistivity changes, and the electrical signal output proportional to the force change can be obtained through the measurement circuit. It is also known as a diffused silicon piezoresistive tension loadcell. It is different from the adhesive strain gauge, which needs to indirectly feel the external force through the elastic sensitive element, but directly feels the measured tension through the silicon diaphragm.

 

Piezoresistive tension loadcells are mainly based on the piezoresistive effect. The piezoresistive effect is used to describe the change in resistance of a material under mechanical stress. Unlike the piezoelectric effect, the piezoresistive effect only produces impedance changes and does not produce electrical charges.

 

Piezoresistive effects have been found in most metallic and semiconducting materials. Among them, the piezoresistive effect in semiconductor materials is much larger than that in metals. Since silicon is the main raw material of today's integrated circuits, the application of piezoresistive elements made of silicon becomes very meaningful. Silicon's resistance changes not only from the stress-related geometric deformation, but also from the stress-related resistance of the material itself, making its degree factor hundreds of times greater than that of metals. The resistance change of N-type silicon is mainly due to the redistribution of carriers between the conduction band valleys of different mobilities caused by the displacement of its three conduction band valley pairs, which in turn changes the mobility of electrons in different flow directions. The second is due to the change from the effective mass associated with the change in the shape of the conduction band valley. In p-type silicon, this phenomenon becomes more complex and also leads to equivalent mass change and hole conversion.

 

Piezoresistive tension loadcells are generally connected to a Wheatstone bridge through leads. Usually, there is no external tension on the sensitive core, and the bridge is in a balanced state (called zero position). When the sensor is pressurized, the chip resistance changes, and the bridge will lose balance. If a constant current or voltage power supply is added to the bridge, the bridge will output a voltage signal corresponding to the tension, so that the resistance change of the sensor is converted into a tension signal output through the bridge. The bridge detects the change of the resistance value, after amplification, and then through the conversion of voltage and current, it is converted into a corresponding current signal, and the current signal is compensated by the nonlinear correction loop, that is, the input voltage has a linear corresponding relationship of 4. ~20mA standard output signal.

 

In order to reduce the influence of temperature change on the core resistance value and improve the measurement accuracy, the tension loadcell adopts temperature compensation measures to maintain a high level of technical indicators such as zero drift, sensitivity, linearity, and stability.