From the time we buy the load cell to the use of the load cell, the quality of the load cell is our most concern. From the performance to whether the sensor is damaged during use, we pay special attention to it. So how can we judge the quality of the load cell? We start from the following two aspects:
Judging method of weighing sensor
1、 Pre judge the performance of symmetrical weight sensor before purchase
① Rated range: the difference between the upper and lower limits of the weighing range. Refers to the difference between no-load and rated load output. If the weight of the weighed object exceeds the rated range, the sensor will be overloaded and the load cell will be damaged. When purchasing a load cell, you should have a full understanding of the weight of the weighing object.
② Sensitivity: the sensitivity of the load cell, usually 2mV / v. The sensitivity range of load cells with different structures will be different, which is directly related to temperature factor, selection of strain gauge, elastomer material, structure and design.
③ Input / output impedance: the impedance of the load cell has an impact on the service life. In order to reduce loss and prolong service life, high impedance load cell shall be selected as far as possible. However, due to the high cost and manufacturing difficulty of high impedance load cell strain gauge, the price will be high. You can choose according to your own needs when purchasing.
④ Insulation impedance: the insulation impedance of the load cell is an important index to judge the quality of the load cell. Insulation impedance reflects the quality of the material. If the environment is bad, his importance can be more prominent.
⑤ Elastomer: the material of elastomer is also a factor to be considered. There are many optional materials for the load cell, which is nothing more than selecting the one suitable for yourself in combination with your own industry needs and the impact of the environment.
⑥ Manufacturer factor: there must be experienced technical and resource support behind high-quality weighing sensors. These technical support can guarantee the stability and service life of the output weighing sensors, so it is necessary to select a powerful weighing sensor manufacturer.
The weighing sensor
2、 Judge the quality of the load cell during use
The load cell is an easily damaged element in the weighing unit. It is easy to damage the sensor due to impact, overload, aging, high temperature, corrosion and other reasons.
① Physical observation: observe whether the appearance of the load cell is deformed, cracked, etc.
② Measuring resistance: after measuring the input and output resistance of the load cell with a multimeter, if there is a big difference compared with the manual, the sensor will be damaged. If there is no instruction, it shall be determined by the resistance value.
1: Input resistance ≥ output resistance > bridge resistance
2: The bridge resistance is equal or equal in two
(the input resistance is the resistance from exc + to exc -, the output resistance is the resistance from sig + to sig -, the bridge resistance is the resistance from exc + to sig +, exc + to sig -, exc – to sig +, exc – to sig -)
Thus, it can be determined whether the load cell is damaged.
③ Measuring voltage
First, measure the voltage between the instrument terminals exc + and exc – within the DC voltage range of the multimeter, which is the excitation voltage of the load cell. Under normal circumstances, the excitation voltage (between exc + and exc -) is 5-10v. Now, taking DC5V as an example, the output sensitivity of the load cell we contact is generally 2mV / V, that is, the linear relationship between the excitation voltage of each 1V of the load cell output signal and 2mV.
When the equipment is unloaded, the output voltage (between sig + and sig -) is close to 0, which is less than the maximum output of the sensor. (the maximum output of the sensor = excitation voltage * sensor sensitivity, and the sensor sensitivity of the load cell is mostly 2mV / V). If it exceeds this range, replace the sensor.)
Judge whether the load cell is good or bad with a multimeter
There are many causes of load cell failure, and sometimes several faults may occur at the same time. In addition to the above conditions, there are also damages caused by power supply, external magnetic field interference and other reasons. Therefore, in the process of on-site use and commissioning, there must be a standardized operation process, which can greatly reduce the fault problem. Standardized operation and safe production.