The Precision Issue of Peristaltic Pump and Constant Flow Pump

        The precision of peristaltic pumps and constant flow pumps is between 0.5% to 1%. There are two common issues that users often encounter:

1. Even though the precision of peristaltic pumps can reach this level, why is it sometimes not possible to achieve this precision when dispensing less than 2ml, but it is achievable when dispensing more than 2ml?

2. When the speed of the pump head is low, why does the liquid in the pump tube appear to stop flowing visually?

        Here are the answers:

1. Peristaltic pumps generate a constant flow output by squeezing the flexible tube with rotating wheels. Each complete rotation of the wheel produces a fixed volume of fluid. However, during the rotation of the peristaltic pump wheel, each time it leaves the tube, the liquid will be sucked back due to the elasticity of the tube, resulting in a sudden decrease in discharge flow, known as pulses. If a peristaltic pump has multiple compression wheels, there will be multiple pulses at the discharge port. For example, if our pump has two compression wheels and produces 3ml of flow per rotation, if you need to dispense 1ml, it means the pump only needs to rotate for about 1/3 of a full cycle. Due to the presence of pulses from the peristaltic pump wheel, it is impossible to ensure the reproducibility of flow within one full cycle. As long as the dispensing flow rate of the peristaltic pump is greater than the flow rate produced by each rotation, when the peristaltic pump stops dispensing, it will always stop at the point where it started last time.

        Conclusion: The dispensing flow rate of peristaltic pumps should be selected to exceed the flow rate produced by each rotation of the peristaltic pump wheel.

2. When the speed of the pump head is low, and you observe a pause in the flow of liquid at the inlet of the pump, this is due to the fact that when the rotating wheel first presses against the tube, the internal space of the tube becomes smaller, causing the liquid to be pushed back. This results in a cancellation of the forward flow of liquid by the backward flow. However, this does not affect the normal discharge of liquid, so the discharge accuracy remains constant.

        Therefore, we do not need to worry about any pulses at the outlet or pauses at the inlet during dispensing and transportation processes, as they do not affect the accuracy of fluid transport."