Introduction of filling accuracy of peristaltic pump
A summary of the knowledge of the peristaltic pump, how to improve the filling accuracy of the peristaltic pump? The so-called filling is the process of transferring a certain amount of liquid within a specified time. The filling accuracy error refers to measuring the filling volume of each filling after multIPLe fillings. The formula is: filling accuracy = (maximum value-minimum value)/average value. Therefore, to ensure the consistency of each filling volume is to improve the filling accuracy. Since the stepper motor is easy to control the angle, the running speed is not affected by the load, and can be made into a more accurate open-loop control system, so the general filling system is driven by a stepper motor. The technologies currently used in the peristaltic pump filling market are not the same. Now I will mainly talk about the characteristics of various technologies: First: Use a time timer to control the filling volume. This method is the easiest to implement, but the error is also large. The main reasons are the influence of temperature and the influence of program structure. The single-chip microcomputer works by the frequency output of the crystal oscillator, and the temperature has an influence on the crystal oscillator frequency. A good crystal oscillator can minimize the impact, but it cannot be eliminated. This influence directly determines the size of the timer time base in the single-chip microcomputer, thereby affecting The set time length causes the inconsistency of the working time of the peristaltic pump each time, thus causing errors. In addition, it is not advisable to use the program to accurately generate the time value. When working, the influence of various interrupt operations will cause the time error, and this error is unpredictable and cannot be compensated. Second: Use the number of pulses to control the filling volume. This method can ensure that the total number of operating angles of the peristaltic pump for each distribution is the same, and the filling accuracy is much improved relative to the time control method. However, due to the pulsation phenomenon of the peristaltic pump when transferring liquid, although the number of pulses can be used to control the total operating angle, the instantaneous flow rate is at the peak or trough of the pulsation or a certain flow rate in the middle is uncertain, that is, the position when the roller stops. The position is inconsistent after one allocation. This will cause distribution errors due to the different stopping positions of the rollers each time. This kind of distribution error is relatively small compared to the larger amount of liquid being distributed, mainly because it will have a great influence on the distribution of a smaller amount of liquid. Third: Use angle control technology to control the filling volume. This method uses the number of pulses to control the filling volume based on the addition of angle control technology during shutdown to ensure that the peristaltic pump rollers are in the same position every time the peristaltic pump is shut down, thus eliminating the influence of the peristaltic pump pulsation on the filling volume. , It is very obvious improvement to the filling of small flow. The above three filling technologies are all open-loop control, and the flow attenuation factor of the peristaltic pump hose is not considered. In actual work, it should be calibrated regularly to achieve higher filling accuracy.
