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Basic Methods and Requirements to Ensure the Accuracy of Dynamic Checkweighers

Basic Methods and Requirements to Ensure the Accuracy of Dynamic Checkweighers

Issue Time:2021-11-09
the basic methods and requirements to ensure the accuracy of the dynamic checkweigher
The accuracy of the dynamic checkweigher is related to whether the qualified rate of the product meets the standard, and it is also a key factor for testing the quality of a checkweigher. We can improve the accuracy of the checkweigher through the following measures.

Guarantee accuracy by guaranteeing the passing state of the inspected product

Due to the diversity of the tested products, the state of the weighing part of the tested object passing through the dynamic checkweigher has a great influence on the accuracy of the checkweigher. Before a batch of test objects pass the checkweigher, there must be an equidistant separation process, and the spacing must be as large as a certain value.

It is necessary to ensure that the next product can touch the weighing table after the previous product completely leaves the weighing table, that is, to ensure that only one object to be tested enters the weighing table at a time.

This can be achieved by increasing the conveying speed of the checkweigher, forming a speed difference with the previous conveying equipment, extending the distance between products to a certain extent, and ensuring the weighing requirements of the checkweigher.

The stability of the tested product on the weighing table is also an important factor affecting accuracy. When the inspected product enters the weighing part through the introduction conveyor, a smooth transition must be ensured.

First, adjust the speed of the lead-in conveyor to the same speed as the weighing table conveyor, and minimize the speed difference as much as possible to ensure a smooth transition of the inspected products when they pass the connecting position.

In addition, due to the diverse appearance of the test object, if the center of gravity is too high or the area of the bottom contacting the table is too small, it may tilt or jump when passing the joint position, causing the weighing table to shake and affect the accuracy. In this case, you can add transitional equipment at the converging position of the conveyor.

Another important factor that affects the accuracy of the dynamic checkweigher is the conveying speed of the product being tested. From the perspective of production operations, in order to improve production efficiency, we always hope to speed up the production line as much as possible.

But for the dynamic checkweigher, the contradiction between speed and accuracy has always existed. The faster the speed, the more difficult it is to guarantee accuracy.

The residence time (effective weighing time) of the tested product in the weighing part should reach a certain length, and this time must meet the requirement of the instrument controller for the number of sampling points of the load cell signal. If the signal sampling time is too short and the number of sampling points is too low, the instrument controller cannot calculate the precise arithmetic average value, and thus cannot guarantee the accuracy of the weighing result.

The conveying speed can be appropriately reduced, or the length of the weighing table can be appropriately increased within the allowable range, and the weighing time can be increased to ensure that the minimum number of sampling points of the instrument controller is met. On this basis, accurate calculations can be achieved. To a certain extent, the weighing accuracy is guaranteed.

Ensure accuracy by improving the equipment operating environment

The dynamic checkweigher is a high-precision re-inspection equipment, usually, the weight value of the test object is very small, and the weighing accuracy will be more sensitive in the state of high-speed operation, and it is affected by many environmental factors.

For example, the temperature, humidity, electrostatic induction, radio frequency interference, ground vibration, air circulation, etc. of the working environment. Therefore, the use environment of the dynamic checkweigher is also a key factor to ensure accuracy.

First of all, try to place the dynamic checkweigher in a suitable and constant working environment with suitable temperature and humidity to avoid unstable and irregular changes in various indicators. If necessary, an electric heating device can be added to the load cell module to directly control the working environment of the load cell.

Electrical equipment should be well-grounded to reduce electrostatic induction, stay away from strong radiation, and avoid wireless electromagnetic interference. Airflow will also have a certain impact on the accuracy of the dynamic checkweigher. It is best to install the equipment in a windproof production workshop and add a windshield at the weighing position to effectively improve the stability of the equipment operation.

Ensure accuracy by improving production technology

The working state of the dynamic checkweigher is to carry out weighing under the condition of high-speed operation, which puts forward higher stability requirements for the conveying equipment participating in the weighing.

Therefore, the conveying mechanism of the weighing part must minimize the noise and vibration during operation, which requires the static balance and dynamic balance experiments of the driving roller and the driven roller of the conveyor before assembly. The experiment needs to be repeated, and the roller is modified with counterweight until the deviation value is reduced to the range of the design requirements. This is also a key factor to ensure weighing accuracy.

The load cell is the core component of the dynamic checkweigher, and the most common in industrial applications is the strain gauge sensor. This is a sensor that uses resistance strain gauges to convert strain into resistance changes. It is widely used in various fields of weighing.

However, with the development and progress of science and technology, new devices with higher technological content such as electromagnetic compensation sensors have appeared in the sensors currently used in dynamic checkweighers.

The working principle of the electromagnetic compensation sensor: When a weight is placed on the weighing pan, the balance of the system will be broken. 

At this time, the displacement sensor will output a position change signal to the current regulator, and the current regulator will adjust the output current in time to increase the current flowing through the wire until the electromagnetic force generated by it and the gravity of the weight cancel each other out. The electromagnetic compensation sensor is characterized by the faster response and higher accuracy.

The rejection part and the sorting part are also important parts of the dynamic checkweigher. In the process of online work, the detection of unqualified or different weight grade products needs to respond accurately and quickly in the shortest time. Excessive mechanical action or excessive force will cause a certain amount of vibration, which will affect the weighing accuracy of the checkweigher.

We can separate the frame of the rejected or sorted part from the overall frame of the checkweigher, and fix the distance between it and the checkweigher through a soft connection to minimize the impact caused by mechanical movement. The impact of vibration on accuracy.

If you want to know more about the dynamic checkweigher after reading the above, you can contact us for a comprehensive solution.

As a professional supplier of checkweighing and inspection systems, we are constantly optimizing and adjusting solutions based on customer needs. We have a professional production department and a complete management system and carry out strict quality inspections on all aspects of our products. Our thoughtful one-stop service has also won praise and trust from many customers. If you are interested in our checkweigher, please contact us immediately!

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