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Shanghai Qianfeng Electronic Instrument Co., Ltd

Precautions for using sensors in electronic scales

2023-10-27 15:29:28

Electronic scales typically require the use of weighing sensors. In order to ensure the accuracy of testing, Nanjing Weighing Instrument introduced several issues that need to be noted:

1. The sensor should use hinged copper wire (with a cross-sectional area of approximately 50mm2) to form an electrical bypass to protect it from hazards caused by welding current or lightning strikes. During the use of sensors, it is necessary to avoid strong thermal radiation, especially on one side.

2. Handle carefully, especially for small capacity sensors made of alloy aluminum elastic system. Any impact or drop may cause significant damage to its metrological performance. For large capacity weighing sensors, generally speaking, their self weight is relatively large, so it is necessary to use suitable lifting equipment (such as chain cranes, 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 stiffness, usually requiring higher strength and hardness than the sensor itself.

3. All wires connecting or leading out display circuits should be shielded cables. The connection and grounding point of the shielding wire should be reasonable. If it is not grounded through a mechanical frame, it is externally grounded, but the shield wires are not grounded after being connected to each other, which is floating. Note: The three sensors are completely parallel, and the sensor itself is a 4-wire system, but a 6-wire system connection is used instead in the junction box. The sensor output signal readout circuit should not be placed in the same box as devices that may cause strong interference (such as control silicon and contactors) and devices that generate a large amount of heat. If this cannot be guaranteed, consideration should be given to barrier isolation between them and installing fans 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 devices such as contactors.

4. Try to set up some "baffles" around the weighing sensor, or even cover the sensor with thin metal plates. This can prevent debris from contaminating sensors and certain movable components, which usually makes the movement of movable components uncomfortable and affects weighing accuracy. The following methods can be used to determine whether the system feels uncomfortable during movement. That is to say, add or subtract approximately one thousandth of the rated load on the weighing platform to check if the electronic floor scale weighing display device reflects that the movable part is not "contaminated".

5. Horizontal adjustment: There are two aspects to horizontal adjustment. One method is to use a liquid level gauge to horizontally adjust the installation plane of a single sensor mounting base. On the other hand, this means that the installation surfaces of multiple sensor mounting bases should be adjusted to the same level as much as possible (using liquid level gauges), especially in weighing systems with more than three sensors. The main purpose of doing so is to ensure that the load borne by each sensor is basically consistent. The loading direction of each electronic weighbridge weighing sensor is determined, and when we use it, we must load in this direction. Lateral forces, additional bending moments, and torques should be avoided as much as possible.

6. Try to use structural attachments with automatic positioning (reset) function, such as spherical 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 force, and lateral forces caused by vibration of agitators on certain container scales, which are not caused by mechanical equipment. Some scales must be connected to accessories on the scale body (such as the feed line of the container scale). 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.

Although the weighing sensor has a certain overload capacity, it should still be prevented from overload during the installation process of the weighing system. It should be noted that even short-term overload may cause permanent damage to the sensor. During the installation process, if necessary, the sensor can be replaced with a cushion block of the same height as the sensor first, and then the sensor can be replaced. During normal operation, sensors should usually be equipped with mechanical structural components for overload protection