How to identify the performance of the negative pressure blower

As the demand of negative pressure blowers is increasing, some manufacturers always sell seconds at best quality prices, then how can we identify their quality from their performances when purchasing negative pressure blowers? 

Dynamic balance is the basis of guaranteeing the negative pressure blowers to work effectively. Negative pressure blowers with excellent quality have low vibration and low noise during the operation process, which can greatly improve their working efficiency. 

For the treatment of noise, enterprises can judge the noise from the sound change of the negative pressure blower during the working process. 

When observing the air volume of the negative pressure blower, enterprises can judge the air volume by observing the blade condition of the front louver and the air pressure during the operation of the negative pressure blower. 

The determination of current can be used to judge whether the negative pressure blower meets the technical standards.