Load cell precautions - Solutions - Huaqiang Electronic Network

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In the daily life, the use of load cells is becoming more and more common. What should you pay attention to when using load cells? Because the resistance strain gauge load cell itself is a rugged, durable and reliable electromechanical product. However, in order to ensure the accuracy of the test, there are still many problems to be paid attention to in use. Some basic requirements are listed below. It is necessary to handle it lightly, especially the small-capacity sensor made of alloy aluminum. Any impact or drop can cause great damage to its metering performance. For large-capacity load cells, in general, it has a large self-weight, so it is required to use appropriate lifting equipment (such as chain hoists, electric hoists, etc.) when handling and installing. The mounting surface of the base on which the sensor is mounted should be flat and clean, without any oil film, film, etc. The mounting base itself should have sufficient strength and rigidity and is generally required to be stronger than the strength and stiffness of the sensor itself.

Level adjustment: There are two aspects to the level adjustment. First, the mounting plane of the single sensor mounting base should be leveled with a level. On the other hand, the mounting surface of the mounting base of multiple sensors should be adjusted to a horizontal surface (water level gauge), especially the number of sensors is more than three. In the weighing system, this should be noted. The main purpose of this is to make the load on each sensor basically the same. The load direction of each load cell is determined, and we must load the load in this direction when we use it. Lateral forces, additional bending moments, and torque forces should be avoided as much as possible with structural components that have automatic positioning (reset), such as spherical bearings, joint bearings, and positioning fasteners. They can prevent some lateral forces from acting on the sensor. It should be noted that some lateral forces are not caused by mechanical installation, such as lateral forces caused by thermal expansion, lateral forces caused by wind, and lateral forces caused by vibration of the agitator on some container scales are not caused by mechanical installation. . Some of the scales must be attached to the scale body (such as the container pipe of the container scale), we should let them be as soft as possible in the direction of the sensor loading the spindle to prevent them from "eat" the true load of the sensor. Combined to cause errors.

Some "baffles" should be placed around the load cell, and even the thin metal plate should be used to cover the sensor. This prevents debris from smudging the sensor and some moving parts, and this "staining" tends to make the movable part uncomfortable and affects the weighing accuracy. Whether the system has motion or not, can be judged by the following method. That is, add or subtract about one thousandth of the rated load on the weighing platform to see if the weighing indicator is reflected, and there is a reflection that the movable part is not "stained". Although the load cell has a certain overload capacity, the overload of the sensor should be prevented during the installation of the weighing system. It should be noted that even a short overload may cause permanent damage to the sensor. During the installation process, if it is necessary, you can replace the sensor with a height block such as a sensor. At the end, replace the sensor. In normal operation, the sensor should generally be provided with mechanical components for overload protection. If the screw is used to fix the sensor, a certain tightening torque is required, and the screw should have a certain screwing depth. In general, the fixed screw uses a high-strength screw. The sensor shall be electrically bypassed with hinged copper wires (approximately 50 mm2 cross-section) to protect them from welding currents or lightning strikes. In the use of the sensor, strong thermal radiation must be avoided, especially on the one side. 1. Electrical connection (such as the signal cable of the sensor, not in parallel with the strong power line or control line (for example, do not put the sensor signal line and the strong power line and control line in the same pipe). If they must be in parallel Place them, then the distance between them should be kept above 50CM, and the signal wires should be covered with metal tubes.

In any case, the power cord and control line should be twisted together to a degree of 50 rpm. If the sensor signal line needs to be extended, a special sealed cable junction box should be used. If such a junction box is not used, and the cable and the cable are directly butted (soldered end), special attention should be paid to the sealing and moisture proof. After the connection, the insulation resistance should be checked and the standard (2000-5000M) should be met. If necessary, The sensor should be recalibrated. If the signal cable is long and high measurement accuracy is to be ensured, a cable compensation circuit with a relay amplifier should be considered. Shielded cables should be used for all wires leading to or from the display circuit. The connection and grounding point of the shielded wire should be reasonable. If it is not grounded through the mechanical frame, it is grounded externally, but the shielded wires are not grounded after being connected to each other and are floating. Note: There are 3 sensors that are fully connected. The sensor itself is a 4-wire system, but it is replaced by a 6-wire connection in the junction box. The sensor output signal readout circuit should not be placed in the same cabinet with devices that can generate strong interference, such as silicon, contactors, etc., and if there is no guarantee of heat generation, they should be considered. The baffle is isolated and a fan is placed in the box. The electronic circuit for measuring the output signal of the sensor should be equipped with an independent power supply transformer as much as possible, instead of sharing the same main power supply with devices such as contactors. If used, it will be more accurate, more convenient, and will not be easily damaged.