Several problems that must be paid attention to in

Several problems that must be paid attention to in the use of load cells

the use of load cells is omnipresent in modern science and technology industry, because the resistance strain load cell itself is a solid, durable and reliable electromechanical product, but in order to ensure the test accuracy, there are still many problems that should be paid attention to in use, so what should be paid attention to when using load cells? Here are nine aspects that must be paid attention to in the use of load cells:

1 Try to set some "baffles" around the weighing sensor, and even cover the sensor with thin metal plates. This can prevent sundries from contaminating the sensor and some movable parts, and this "contamination" will often make the movable parts uncomfortable and affect the weighing accuracy. The following methods can be used to judge whether the system has uncomfortable movement. That is, add or subtract about one thousandth of the rated load on the scale platform to see if the weighing display reflects. If so, it means that the movable part is not "contaminated"

2. All conductors leading to or from the display circuit shall be shielded cables. The connection and grounding point of shield wire shall be reasonable. If it is not grounded through the mechanical frame, it is grounded externally, but the shield wire is not grounded after being connected with each other, which is floating. Note: three sensors are connected in full parallel. The sensor itself is a 4-wire system, but it is replaced by a 6-wire system in the junction box. Sensing and huge market demand device output signal readout circuit should not be placed in the same box with devices that can produce strong interference (controllable silicon, contactors, etc.) and devices that generate considerable heat. If this cannot be guaranteed, barrier plates should be set between them for isolation, and fans should be placed in the box. The electronic circuit used to measure the output signal of the sensor should be equipped with an independent power supply transformer as far as possible, rather than sharing the same main power supply with equipment such as contactors

3. The sensors shall adopt stranded 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 strike. During the use of the sensor, strong thermal radiation, especially on one side, must be avoided

4. Electrical connection equipment (such as the signal cable of the sensor, which is not arranged in parallel with the strong current power line or control line) (for example, do not put the sensor signal line, strong current power line and control line in the same pipe). If they must be placed in parallel, the distance between them should be kept above 50cm, and the signal line should be sheathed with metal tubes

5. Try to use structural accessories with automatic positioning (reset) function, such as ball bearings, joint bearings, positioning fasteners, etc. They can prevent some lateral forces from acting on the sensor. It should be noted that some transverse forces are not caused by mechanical installation, such as the transverse force caused by thermal expansion, the transverse force caused by wind, and the transverse force caused by the vibration of the agitator on some container weighing instruments, that is, they are not caused by mechanical installation. Some weighing instruments must be connected to the accessories on the scale body (such as the feeding pipe of the container scale). We should make them as soft as possible in the direction of the sensor loading spindle, so as to prevent them from "eating" the real load of the sensor and causing errors

6. Handle with care, especially the small capacity sensor made of alloy aluminum elastomer. Any impact or fall may cause great damage to its metering performance. Generally speaking, the weighing sensor with large capacity has a large self weight, so it is required to use appropriate lifting equipment (such as chain block, electric hoist, etc.) as much as possible during handling and installation. The mounting surface of the base for installing the sensor should be flat and clean without any oil film, rubber film, etc. The mounting base itself should have sufficient strength and rigidity, which is generally higher than that of the sensor itself

7. Although the weighing sensor has an overload capacity with uncertain speed control, the overload of the sensor should still be prevented during the installation of the weighing system. It should be noted that even a short-term overload may cause permanent damage to the sensor. In the process of installation, if necessary, replace the sensor with a cushion block at the same height as the sensor, and finally replace the sensor. In normal operation, the sensor should generally be equipped with mechanical structural parts of overload protection. If the sensor is fixed with a screw, it is required to have a certain tightening torque, and the screw should have a certain screw depth. Generally speaking, the fixed screw adopts high-strength screw

8. In any case, the power line and control line should be twisted 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, but the cable is directly connected with the cable (soldering end), special attention should be paid to the sealing and moisture resistance. After the connection, the insulation resistance should be checked and the standard (2000 ~ 5000m) should be reached. If necessary, the sensor should be recalibrated. If the signal cable is long and the measurement accuracy is high, the cable compensation circuit with relay amplifier should be considered

9. Horizontal adjustment: horizontal adjustment has two aspects. First, the installation plane of the mounting base of a single sensor should be adjusted horizontally with a level gauge. On the other hand, the mounting surface of the mounting base of multiple sensors should be adjusted to a horizontal plane as much as possible (with the level, the plastic rope used in our life (in some places, begging and learning rope) is made of linear polyethylene or polypropylene), especially in the weighing system with more than three sensors, we should pay more attention to this point, The main purpose of this is to make the load borne by each sensor basically consistent. The loading direction of each weighing sensor is determined, and when we use it, we must load in this direction. Lateral force, additional bending moment and torque force should be avoided as far as possible

if you operate in strict accordance with the above, the measurement results of the weighing sensor will be more accurate and convenient when used, and the weighing sensor will not be easily damaged, and the service life and maintenance can be better! (end)