Precautions for using weighing sensors

Precautions for using weighing sensors

The resistance strain type weighing sensor itself is a sturdy, durable, and reliable electromechanical product. However, in order to ensure testing accuracy, there are still many issues that need to be noted during use. Below are some basic requirements. Electrical connection aspect
The signal cable of the sensor should not be arranged in parallel with the high-voltage power line or control line (for example, do not place the sensor signal line, high-voltage power line, and control line in the same pipeline). If they must be placed in parallel, the distance between them should be kept at least 50cm, and the signal lines should be covered with metal tubes. In any case, the power and control wires should be twisted together at a speed of 50 revolutions per meter. If the sensor signal wire needs to be extended, a specially sealed cable junction box should be used. If this type of junction box is not used and cables are directly connected (soldered ends), special attention should be paid to sealing and moisture resistance. After connection, the insulation resistance should be checked and meet the standard (2000~5000M). If necessary, the sensor should be recalibrated. If the signal cable is very long and high measurement accuracy needs to be ensured, a cable compensation circuit with a relay amplifier should be considered.

All wires leading to or from the display circuit should use shielded cables. The connection and grounding points of shielded wires should be reasonable. If it is not grounded through the mechanical frame, it will be grounded externally, but if the shielding wires are connected to each other and not grounded, it will be floating. Note: There are 3 sensors that are fully connected in parallel. The sensors themselves are 4-wire, but they have been replaced with a 6-wire connection in the junction box. The sensor output signal readout circuit should not be placed in the same box as devices that can cause strong interference (such as controllable silicon, contactors, etc.) or devices that generate considerable heat. If this cannot be guaranteed, it is necessary to consider setting up barriers to isolate them
And install a fan inside the box. Electronic circuits used to measure sensor output signals should be equipped with independent power transformers as much as possible, rather than sharing the same main power supply with equipment such as contactors.
Mechanical installation aspect
Weighing sensors should be handled with care, especially small capacity sensors made of alloy aluminum elastomers. Any impact or drop may cause significant damage to their measuring performance. For high-capacity weighing sensors, they generally have 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 transportation and installation. The installation surface of the sensor base should be flat, clean, and free of any oil film, adhesive film, etc. The installation base itself should have sufficient strength and rigidity, generally requiring higher strength and rigidity than the sensor itself.

Horizontal adjustment: Horizontal adjustment has two aspects. One is that the installation plane of a single sensor mounting base needs to be adjusted horizontally with a level, and the other is that the installation surfaces of multiple sensor mounting bases should be adjusted to a horizontal plane as much as possible (using a level), especially in weighing systems with more than three sensors. The main purpose of this is to ensure that the loads borne by each sensor are basically the same. The loading direction of each weighing sensor 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.
Try to use structural components with automatic positioning (reset) function, such as ball bearings, joint bearings, positioning fasteners, etc. They can prevent certain 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 agitators on certain container scales, which are not caused by mechanical installation. Some accessories on certain scales must be connected to the scale body (such as the feeding pipeline of container scales). We should make them as soft as possible in the direction of the sensor loading spindle to prevent them from "eating" the true load of the sensor and causing errors. Try to set up some "baffles" around the weighing sensor, and even cover the sensor with thin metal plates. This can prevent impurities from contaminating the sensor and certain movable parts, which often cause discomfort in the movement of the movable parts and affect the weighing accuracy.

The presence or absence of motion discomfort in the system can be determined using the following methods. Add or subtract approximately one thousandth of the rated load on the weighing platform to check if the weighing display reflects. If it does, it indicates that the movable part is not "contaminated". Although the weighing sensor has a certain overload capacity, it should still be prevented from overloading during the installation of the weighing system. It should be noted that even short-term overloading may cause permanent damage to the sensor. During the installation process, if necessary, a pad of the same height as the sensor can be used to replace the sensor first, and then the sensor can be replaced at the end. During normal operation, sensors should generally be equipped with mechanical structural components for overload protection. If a screw is used to fix the sensor, a certain tightening torque is required, and the screw should have a certain depth of thread insertion. Generally speaking, fixed screws use high-strength screws.
Sensors should use hinged copper wires (with a cross-sectional area of approximately 50mm2) to form an electrical bypass to protect them from the hazards caused by welding currents or lightning strikes.
During the use of sensors, it is necessary to avoid strong thermal radiation, especially on one side.