Blog

Load Cell Technical Parameters

The characteristics of foreign weighing load cell technology development and the reasons for its rapid development:

(1). Pay attention to the research of basic technology, basic technology and common key technology, do basic research and pre-research in parallel; common key technology research and application technology research in parallel; typical product development and product engineering in parallel. Ensure that basic technology and basic processes (resistance strain gauges, strain adhesives, compensation components, protection and sealing materials, etc.) have always been in the world’s leading position.

(2) Pay attention to the research and application of infrastructure construction and manufacturing technology and manufacturing process. Equipped with excellent process equipment and testing instruments, especially intelligent process equipment, the most advanced process equipment;

(3) Aiming at the development trends and strategic frontiers of the world’s load cell technology, and determining the research topics and product development directions. Attach importance to the development of new products and products with independent intellectual property rights to enhance core competitiveness. The standards for technological innovation and new product development are: high technological leadership, technological advancement, market proliferation, and benefit proliferation. The technology and craftsmanship is always in the leading position in the world.

(4) Pay attention to the reliability design, control and management of the load cell, strictly design compliance control and process reliability control, and strive to make the process fulfillment rate reach 100%.

(5) Pay attention to market competition, strengthen market investigation and analysis, and respond quickly to the market. Market competition in the 21st century is focused on market response speed and based on improved and innovative products.

(6) Pay attention to the study of relevant laws and regulations, fully understand and implement them carefully, to ensure that every product produced meets the requirements.

The technical parameters of the load cell include rated load, allowable load, limit load, sensitivity, non-linearity, repeatability, allowable use temperature, zero temperature effect, temperature effect of output sensitivity coefficient, output impedance, input impedance, insulation resistance, and maximum allowable Excitation voltage, hysteresis, creep and creep recovery, sealing protection level, cable length.

 

1. Rated load: the maximum axial load that the load cellcan measure within the specified technical index range. But in actual use,

Generally only use 2/3~1/3 of the rated range.

2. Allowable load (or safe overload): the maximum axial load allowed by the load cell. Allowed in certain

Overload work within the range. Generally 120%~150%.

3. Ultimate load (or ultimate overload): the maximum axial load that the load cell can withstand without losing its ability to work

Lotus. This means that when the work exceeds this value, the load cell will be damaged.

4. Sensitivity:

The ratio of the output increment to the added load increment. Usually the mV of the rated output per input voltage of 1V.

5. Non-linearity:

This is a parameter that characterizes the accuracy of the corresponding relationship between the voltage signal output by the load cell and the load.

6. Repeatability:

Repeatability characterizes whether the output value of the load cell can be repeated and consistent when the same load is repeatedly applied under the same conditions. This feature is more important and can better reflect the quality of the load cell. The national standard’s description of repeatability error: repeatability error and nonlinearity can be measured at the same time as the maximum difference between the actual output signal values ​​of 3 measurements on the same test point.

7. Allowable operating temperature:

It specifies the occasions where this load cell can be applied.

For example, the normal temperature load cell is generally marked as: -20℃- +70℃. The high temperature load cell is marked as: -40℃-250℃.

Temperature compensation range: It means that the load cell has been compensated in this temperature range during production. Normal temperature

The load cell is generally marked as -10℃- +55℃.

8. The influence of zero temperature (commonly known as zero temperature drift):

Characterize the stability of the load cell’s zero point when the ambient temperature changes. Generally, the unit of measurement is the drift produced in the range of every 10°C.

9. Temperature influence of output sensitivity coefficient (commonly known as coefficient temperature drift):

This parameter characterizes the stability of the output sensitivity of the load cell when the ambient temperature changes. Generally, the unit of measurement is the drift produced in the range of every 10°C.

10. Output impedance:

Under rated technical conditions, the output resistance of the load cell S+ S- [I+ I-]

11. Input impedance:

The resistance value of the excitation terminal of the load cell, E+ E- [V+ V-]

12. Insulation resistance:

The insulation resistance between the circuit part of the load cell and the elastic beam, the larger the better, and the insulation resistance will affect the performance of the load cell. When the insulation resistance is lower than a certain value, the bridge will not work properly. Recommended excitation voltage: generally 5-12 volts. Because the stabilized DC power supply in the general weighing instrument is 5 or 12 volts.

13. The maximum allowable excitation voltage:

The maximum supply voltage that the load cell can withstand. The maximum excitation voltage is not recommended.

14. Lag:

The popular meaning of lag is: when the load is applied step by step and then the load is unloaded in turn, the corresponding readings of each load should ideally have the same reading, but in fact it is consistent. The degree of inconsistency is represented by the indicator of lag error.

In the national standard, the hysteresis error is calculated as follows: the maximum difference (mv) between the arithmetic average of the actual output signal value of 3 trips and the arithmetic average of the actual output signal value of the 3 trips on the same test point.

15. Creep and creep recovery:

It is required to check the creep error of the load cell from two aspects: one is the creep: the rated load is applied for 5-10 seconds without impact, the reading is 5-10 seconds after the load, and then a certain amount is pressed within 30 minutes. The time interval is to write down the output value in turn. The second is creep recovery: remove the rated load as soon as possible (within 5-10 seconds), immediately read the reading within 5-10 seconds after unloading, and then record the output value in turn at a certain time interval within 30 minutes.

 

Precautions for load cell replacement:

1. As the rated load increases, the output microvolt/division signal of the load cell decreases, instead of increasing the output signal as the rated load increases. This is often overlooked. Therefore, when replacing the load cell, the load cellwith the same load as the original one should be used as much as possible. If you want to replace a larger load, you must pay attention to whether the scale of the weighing display instrument of the electronic scale is adjustable: if it is an old-style display instrument that is not adjustable, it will be replaced by a larger load load cell, and the output microvolt/division The signal becomes small, the full-scale output and display cannot be performed, and the dial adjustment fails to achieve the purpose and cannot be used; if it is a weighing display instrument with an adjustable range (such as the Toledo 8140 series), after replacing it with a larger load load cell, It can be adjusted and used according to the manual by setting the range. At the same time, it should be noted that if the rated load of the load cellis too large, the output microvolt/division signal is too small, which will easily reduce the sensitivity of the scale.
2. For electromechanical scales that install an S-shaped load cellin the second force transmission link (that is, the linkage between the first force transmission lever and the second force transmission lever), please note: the length of the linkage after reinstalling the load cellIt is the same length as the original link. On the other hand, it is necessary to ensure that the first force transmission lever is horizontal and that the connecting rod and the first force transmission lever form a 90 degree angle perpendicular to it. If there is a deviation, it will directly affect the accuracy and sensitivity of the scale. If the link length is too long, there will be a “big scale” phenomenon; if it is too short, there will be a “small scale” phenomenon. At this time, it should also be noted that the link must be in a free hanging state, and cannot rub against other objects, so as not to affect the sensitivity of the scale.
3. The commissioning of the electromechanical integrated scale after replacing the load cellshould be carried out according to the manual of the weighing display instrument on the basis of the accurate commissioning of the mechanical scale.
4. Whether it is an electronic scale or a combined electromechanical scale, after the load cellis replaced, it must be verified before it can be used.

November 26, 2021