Usually we say the micro vacuum pump is a kind of membrane (diaphragm) pump, which can be divided into two categories: water pump and air pump. People often call it micro pump and micro air pump. It is also called sampling pump when it is used for sampling. It uses the motor, piezoelectric and other power to drive the membrane high-speed vibration to pump fluid. In many cases, we need to adjust the flow rate of micro vacuum pump accurately. We often use the following two methods.

1、 Reduce the working voltage of the pump, usually used in brush motor.

The power supply of the micro pump should have the function of voltage stabilization first, and the power should be enough to ensure the voltage stability under the rated condition of the pump. When the input voltage of the pump is reduced, the speed and flow of the motor will also decrease, which is close to the linear relationship. The additional benefit of pump depressurization operation is to delay the wear of motor brush and prolong the service life of motor. But special attention should be paid to whether the pump can run normally after depressurization. If the vacuum at the inlet of the pump is high, the resistance of the downstream pipeline is large, and the load of the pump is large, the motor can not be started after depressurization, and the temperature of the motor will rise, or even be burned out, which will cause potential safety hazard. Generally, pressure reduction is only suitable for small load to regulate the flow. The rated flow rate of micro vacuum pump is measured under the specified upstream and downstream resistance conditions. The actual use conditions of users are different, and the allowable range of pressure reduction and flow regulation should be determined through test. If the user uses, the pipeline resistance, pump load often changes, using the pressure to adjust the flow, easy to appear motor work fatigue or even unable to run, not easy to control.

Two, in the pipeline regulation.

Install flow control valve upstream or bypass valve downstream. This method has a wide range of flow regulation, but its disadvantage is that it increases energy loss and noise. The micro valve needs manual adjustment, which is not easy to control automatically.

The micro membrane pump uses the crank to convert the rotary motion of the motor into the vibration of the membrane. Due to the principle of the mechanism, there are inevitably fluctuations in pressure and flow. On the flow time curve, the instantaneous flow rate of the pump changes in a waveform similar to a sine curve. The instantaneous flow of pump per minute is called average flow. The theoretical average flow rate is related to the size of pump chamber and membrane, film amplitude and motor speed per minute. In practical use, the actual average flow rate of the pump is lower than the theoretical average flow rate because of the leakage of the check valve and other parts, the compressibility of the transported fluid, and the dissolved and evaporated gas in the liquid. The flow speed curve of micro membrane pump has the characteristics of volume pump. Under the condition of constant external resistance, the flow rate is basically proportional to the pump speed. When the discharge flow of the micro membrane pump increases, its head (outlet pressure) will decrease approximately linearly.