The working principle of the negative pressure weighing room

Negative pressure generation and mechanism
When the negative pressure weighing chamber is started, the vacuum pump in the negative pressure system starts to work. The vacuum pump is like a powerful "suction pump", which continuously pumps and weighs the air in the room through the vacuum pipe, which gradually reduces the amount of air in the room, and then causes the indoor air pressure to slowly decrease, and finally creates a negative pressure environment.
In this negative pressure environment, the air pressure of the space in which the weighing tray is located is lower than that of the external environment, and according to the principle of air pressure difference, an upward force will be generated to act on the items placed on the weighing tray. At the same time, the sensor in the weighing room is always ready, once the item is subjected to this upward force, its weight changes, the sensor can keenly perceive this change, and the corresponding weight signal is accurately transmitted to the PLC (programmable logic controller) in the control system. PLC will be by the pre-set program for these signals for data processing, logical judgment, and other operations, and then the processed data is displayed, so that it can achieve high precision weighing. For example, in the pharmaceutical industry, when some trace pharmaceutical ingredients are weighed, the upward force generated by this negative pressure, combined with high-precision sensors, can accurately measure the weight of the drug to ensure the accuracy of the drug ratio, thus ensuring the quality of the drug.
Air circulation and clean assurance
Clean air has a specific circulation mode in the negative pressure weighing room to ensure the high cleanliness of the working area and the negative pressure environment to prevent cross-contamination. First of all, the air will first enter the return air part, here, the return air must first be pre-filtered through the initial effect filter, the initial effect filter is like a "large particle interception net", and will remove large particles of dust such as dust in the air stream, and complete the initial purification of the air.
After the initial effect filter pretreatment of the air, and then through the medium effect filter for secondary filtration, the medium effect filter can further intercept those smaller particles of impurities, etc., fully protect the subsequent high-efficiency filter, to avoid high-efficiency filter due to excessive impurities and too fast loss or blockage, extend its service life.
Then, under the pressure provided by the centrifugal fan, the air is pushed through the high-efficiency filter, and after this key link, the air meets the clean requirements and becomes a clean airflow that meets the standards used in the work area. This clean air will be sent to the bellow body, of which about 90% of the clean air will pass through the uniform air supply network board, and then form a uniform vertical air supply in the working area, the uniform air flow can make the working area maintain a stable air environment, conducive to weighing operation and prevent dust and other flying diffusion. The other about 10% of the clean air flow is discharged from the equipment through the air volume regulation plate.
Since all the airflow involved in the circulation and discharge has been strictly treated by the high-efficiency filter, no matter whether it is air supply or exhaust, there will be no residual dust, effectively avoiding secondary pollution. In addition, after a stable unidirectional flow is formed in the working area if dust is emitted in this area due to weighing operation and other reasons, the dust will be under the influence of unidirectional airflow, and the airflow will be captured by the primary and medium efficiency filter, coupled with 10% exhaust air of the equipment, so that the air pressure in the working area is always maintained as negative pressure relative to the external environment. To ensure that the dust in the area will not spread to the outside, to avoid harm to the external environment and operators, but also to prevent cross-contamination between different materials, for example, in the food industry, when weighing different food additives, you can rely on such air circulation and negative pressure environment to ensure the accuracy of weighing and the additives will not pollute each other.