Electronic platform scales generally require the use of load cells. In order to ensure the accuracy of the test, Yantai Jiajia Instrument introduces several issues that need attention:
1. The load cells should use twisted copper wires (with a cross-sectional area of about 50mm2) to form an electrical bypass to protect them from the hazards caused by welding current or lightning strikes. In the use of the load cell, strong heat radiation must be avoided, especially strong heat radiation on one side.
2. Handle with care, especially the small-capacity load cell made of elastic body made of alloy aluminum. Any impact or drop may cause great damage to its measurement performance. For large-capacity load cells, generally speaking, it has a large self-weight, so it is required to use appropriate lifting equipment (such as chain hoists, electric hoists, etc.) as much as possible during handling and installation. The mounting surface of the base where the load cell is installed should be flat and clean without any oil film or adhesive film. The mounting base itself should have sufficient strength and rigidity, generally higher than that of the load cell itself.
3. All wires leading to or from the display circuit should use shielded cables. 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 load cells that are fully parallel connected. The load cell itself is 4-wire, but it is replaced with 6-wire connection in the junction box. The load cell output signal readout circuit should not be placed in the same box with devices that can generate strong interference (such as silicon controlled devices, contactors, etc.) and devices that generate considerable heat. If this cannot be guaranteed, it should be considered between them. Set up a baffle to isolate it, and install a fan in the box. The electronic circuit used to measure the output signal of the load cell should be equipped with an independent power supply transformer as much as possible, instead of sharing the same main power supply with contactors and other equipment.
4. Try to set some "baffles" around the load cell, or even cover the load cell with a thin metal plate. This can prevent debris from contaminating the load cell and some movable parts, and this "contamination" tends to make the movable parts uncomfortable and affect the weighing accuracy. The following methods can be used to judge whether the system has movement discomfort. That is, add or subtract about one-thousandth of the rated load on the weighing platform to see if the electronic platform weighing display responds, and if there is a reflection, it means that the movable part is not "contaminated".
5. Level adjustment: Level adjustment has two aspects. One is that the installation plane of a single load cell installation base should be adjusted to the level with a spirit level. On the other hand, the installation surface of multiple load cell installation bases should be adjusted to the same level as possible (with a level instrument), especially if the number of load cells is more than three In the weighing system, more attention should be paid to this point. The main purpose of this is to make the loads on each load cell basically the same. The loading direction of each electronic load cell is determined, and when we use it, we must load in this direction. Lateral forces, additional bending moments, and torque forces should be avoided as much as possible.
6. Try to use structural accessories with automatic positioning (resetting), such as spherical bearings, joint bearings, positioning fasteners, etc. They prevent certain lateral forces from acting on the load cell. It should be noted that some lateral forces are not caused by mechanical installation, such as the lateral force caused by thermal expansion, the lateral force caused by wind force, and the lateral force caused by the vibration of the agitator on some container scales is not caused by mechanical installation. There are some accessories on some weighing instruments that must be connected to the scale body (such as the feeding pipe of the container scale, etc.), we should make them as soft as possible in the direction of the load cell loading spindle, so as to prevent them from "eating" the real load of the load cell combine to cause errors.
7. Although the load cell has a certain overload capacity, it should still prevent the load cell from overloading during the installation of the weighing system. It should be noted that even a short period of overloading may cause permanent damage to the load cell. During the installation process, if it is really necessary, the load cell can be replaced with a block with the same height as the load cell, and finally, the load cell can be replaced. In normal operation, the load cell should generally be equipped with mechanical structural parts for overload protection. If the load cell is fixed with a screw, a certain tightening torque is required, and the screw should have a certain screw-in thread depth. Generally speaking, the fixed screw is due to the use of high-strength screws.
8. In any case, the power line and control line should be twisted together, the joint degree is 50 turns/m. If the load cell signal line needs to be extended, a special sealed cable junction box should be used. If this kind of junction box is not used, but the cable is directly connected with the cable (soldered end), special attention should be paid to the sealing and moisture resistance. After the connection is completed, the insulation resistance should be checked and it must meet the standard (2000~5000M). If necessary, The load cell should be re-calibrated. If the signal cable is very long and high measurement accuracy must be ensured, a cable compensation circuit with a relay amplifier should be considered.
9. Prepare for electrical connection (such as load cell signal cables, please do not arrange them in parallel with strong electric power lines or control lines (for example, please do not put load cell signal lines, strong electric power lines and control lines in the same pipeline). If they must be parallel placement, the distance between them should be kept above 50CM, and the signal line should be covered with a metal tube.
Post time: Apr-19-2023