The load cell is a device that converts the quality signal into a measurable electrical signal output. In the basic concepts and evaluation methods of the main technical indicators of load cells, there are qualitative differences between the old and new national standards. There are mainly S type, cantilever type, spoke type, plate ring type, bellows type, bridge type, column cylinder type and so on.
When it comes to weighing sensors, many people think that they are just sensors that measure the weight of objects. In fact, this is not entirely correct. It has also been applied in many fields. The load cell is similar in principle to the previously introduced pressure sensor, but their shape is different. The load cell used in modern science and technology industry is everywhere. The following editor will introduce the application and precautions of load cell.
Load cell application
Electronic weighing instruments made by load cells have been widely used in all walks of life, realizing fast and accurate weighing of materials, especially with the advent of microprocessors, the automation of industrial production processes continues to increase. Heavy sensors have become a necessary device in process control, from weighing large tanks and hoppers that could not be weighed before, as well as measuring and controlling crane scales, automobile scales, etc., to batching systems for mixing and distributing multiple materials, and production The automatic detection in the process and the control of the powder and granular material feed amount are all applied to the load cell. At present, the load cell is used in almost all weighing fields.
Load cell error
1, characteristic error
is caused by the device itself, including DC drift value, incorrect slope or non-linear slope. After all, there will be a gap between the ideal transfer function characteristics of the device and the real characteristics.
2, load cell application error
That is, errors caused by operation, including probe placement errors, incorrect insulation between the probe and the measurement location, errors in the purification process of air or other gases, incorrect placement of transmitters and other operating errors. Error.
3, dynamic error
Sensors suitable for static conditions will have strong damping, so the response to changes in input parameters is slow, and it may even take several seconds to respond to a step change in temperature. Some load cells with delay characteristics will produce dynamic errors when responding to rapid changes. Response time, amplitude distortion, and phase distortion all cause dynamic errors.
4. Insertion error
is the error caused by changing the measurement parameters when a sensor is inserted into the system. Using a transmitter that is too large for the system, the dynamic characteristics of the system is too slow, and the self-heating in the system loads too much heat, etc., will cause insertion errors.
5. Environmental error
The use of the load cell is also affected by the environment such as temperature, swing, vibration, altitude, chemical substance volatilization, etc. These factors can easily cause environmental errors.
Precautions for the use of load cells
Resistance strain gauge load cell is the most widely used type of load cell. Its durability, reliability, and accuracy are beyond doubt. It is precisely because of its characteristics that it will encounter some problems in use. Trouble, what should be paid attention to when using the load cell?
1. Pay attention to the environment
High temperature, dust, humidity, corrosive environment, electromagnetic field environment, etc. will cause serious damage to the load cell and affect it. Therefore, pay attention to the environment in which the load cell is used, or select the corresponding load cell in a given environment.
2, prevent overload
Avoid damage to the load cell caused by overload, even if the load cell has a certain overload capacity.
3, circuit connection
The wires leading to the display circuit or from the circuit should be shielded cables, and the sensor output signal readout circuit should not be placed together with some equipment that can produce interference and high heat.
4, prevent debris from polluting the sensor
Sundries contaminate the sensor may affect the movement and accuracy of the movable part of the sensor. Some "baffles" can be set around the load cell or the sensor can be covered with a thin metal plate.
5. Use electrical bypass
In order to avoid damage caused by welding current or lightning strikes, the sensor should use hinged copper wires (cross-sectional area of about 50mm2) to form an electrical bypass while avoiding strong heat radiation.
6, install level
In order to ensure the accuracy of weighing, the installation plane of the single sensor mounting base should be adjusted with a level gauge. In order to make the load of each sensor basically the same, the mounting surface of the mounting base of multiple sensors should be adjusted to a level surface as much as possible.
7, take it lightly
The load cell should be protected from any impact, drop, etc., handle it gently. At the same time, the base on which the sensor is installed should be flat, clean, with sufficient strength and rigidity, without any oil film, glue film, etc.
8. Prevent certain lateral forces from acting on the sensor
Spherical bearings, joint bearings, positioning fasteners and other structural accessories with automatic positioning or resetting function can be used.
9. The power cord and control cord should be twisted together
The degree of integration is 50 revolutions/m. If the sensor signal line needs to be extended, a special sealed cable junction box should be used. If the signal cable is very long, a cable compensation circuit with a relay amplifier should be considered.
10, electrical connection
The signal cable of the sensor cannot be arranged in parallel with the strong power line or control line.
Conclusion: This is the end of the introduction to the load cell editor. I believe that with the advancement of technology, the load cell will be used in more industry fields with its performance characteristics and advantages, bringing convenience to people's production and life.
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