March 1, 2022

Tension load cell

The most common tension load cellis a resistance strain type, which is a sturdy, durable and reliable sensor product. In order to ensure its accuracy, there are still some problems that need to be paid attention to in the process of installation and use. Here is a brief introduction to you:

1. The tension load cell should be handled with care, especially for the small-capacity sensor using aluminum alloy material as the elastic body, any shock or drop caused by vibration is likely to cause a large output error.
2. When designing the loading device and installing it, it should be ensured that the line of action of the loading force coincides with the force axis of the tension sensor, so as to minimize the influence of the inclined load and the eccentric load.
3. In terms of level adjustment. If you are using a single tension sensor, the installation plane of the base should be adjusted until it is level with a level; if it is a situation where multiple sensors are measuring at the same time, then the installation surface of their base should be kept on a level surface as much as possible. The purpose of this The main purpose is to ensure that the force of each sensor is basically consistent.
4. Determine the rated load of the sensor used according to the range of the tension sensor in this description.
5. The mounting surface of the base of the sensor should be as flat and clean as possible, without any oil stains or film. The mounting base itself should have sufficient strength and rigidity, usually higher than the strength and rigidity of the sensor itself.
6. The housing of the sensor, the protective cover, and the bow/wire connector are all sealed and cannot be opened by the user.
7. In order to prevent chemical corrosion, it is advisable to paint the outer surface of the tension sensor with a wind and soil forest during installation. Avoid direct sunlight and use on sites with drastic changes in ambient temperature. 8. Protective or mitigating devices should be installed when it is unavoidable.
9. In order to prevent high current from directly passing through the sensor body and damaging the sensor, it is forbidden to conduct electric welding after the sensor is installed. 10. Add a bypass made of copper braided wire at both ends of the tension sensor loading device.
11. The cable should not be lengthened by itself. When it is really necessary to lengthen, the joint should be soldered and moisture-proof sealant should be added.
12. It is best to use some baffles around the tension sensor to cover the sensor. The purpose of this is to prevent debris from falling into the moving part of the sensor and affect its measurement accuracy.
13. The cable of the sensor should be far away from the power line of strong power or the place with pulse wave. When the competition cannot be avoided, the cable of the tension sensor should be passed into the iron pipe alone, and the connection distance should be shortened as much as possible.
14. Determine the rated load of the sensor used according to the range of the tension sensor in this description. Although the tension sensor itself has a certain overload capacity, this situation should be avoided as much as possible during installation and use. Sometimes a short-term overload may cause permanent damage to the sensor.
15. In high-precision applications, the tension sensor and instrument should be used after preheating for 30 minutes.

The principle of use of pull pressure sensor:
Industry generally needs to measure various non-electrical physical quantities, such as temperature, pressure, speed, angle, etc., which need to be converted into analog electrical signals before they can be transmitted to a control room or display equipment hundreds of meters away. This device that converts physical quantities into electrical signals is called a tension and pressure sensor. The most widely used in the industry is to use 4-20mA current to transmit analog quantities.

The reason for using the current signal is that it is not easy to be interfered. And the internal resistance of the current source is infinite, and the resistance of the wire in series in the loop does not affect the accuracy, and it can transmit hundreds of meters on the ordinary twisted pair wire. The upper limit is 20mA because of the explosion-proof requirements: the spark energy generated by the 20mA current on and off is not enough to burn gas. The reason why the lower limit is not set to 0mA is to be able to detect disconnection: it will not be lower than 4mA during normal operation. When the transmission line is broken due to a fault, the loop current drops to 0. 2mA is often used as the disconnection alarm value.

The current transmitter converts the physical quantity into a 4-20mA current output, which must be powered by an external power source. The most typical is that the transmitter needs two power cords, plus two current output wires, a total of 4 wires are connected, which is called a four-wire transmitter. Of course, the current output can be shared with the power supply-one wire (common VCC or GND), which can save one wire, which is called a three-wire pull pressure sensor.

In fact, you may have noticed that the 4-20mA current itself can power the transmitter. The pull pressure sensor is equivalent to a special load in the circuit. The special feature is that the current consumption of the pull pressure sensor varies between 4-20 mA according to the sensor output. The display instrument only needs to be stringed in the circuit. This kind of tension and pressure sensor only needs two external wires, so it is called a two-wire tension and pressure sensor. The standard lower limit of the industrial current loop is 4mA, so as long as it is within the range, the pull pressure sensor has at least 4mA power supply. This makes it possible to design a two-wire tension pressure sensor.

In industrial applications, the measurement point is generally on site, while the display device or control device is generally in the control room or control cabinet. The distance between the two may be tens to hundreds of meters. Calculated at a distance of one hundred meters, omitting 2 wires means that the cost is reduced by nearly one hundred yuan! Therefore, the two-wire tension pressure sensor must be the first choice in the application.

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