Ensured accuracy in the fluid dispensing or dosing system is critical to the success of many processes and experiments—from making sure the right amount of crushed tomatoes is added in a spaghetti sauce recipe to dispensing life-saving vaccines into vials. Although the critical volumes in these applications are different, they both rely on some method of metering products with some amount of measurable accuracy. The first step in bringing accuracy to a fluid dispensing system, before even purchasing a pump, is to determine what accuracy is tolerable to your process or experiment. As the above applications illustrated, a lost drop of tomato liquid is not as impactful as a lost drop of vaccine.
Accuracy only follows measurability, so once a tolerance for dispensing accuracy is determined, choose a pump with a measurable output mechanically tied to the motor RPM, otherwise known as a metering pump. Choosing a metering pump such as a peristaltic or diaphragm system is a step in the right direction because metering pumps provide a reliable pattern of “fluid pockets” per revolution. The pump output can be determined mathematically using the volume of the fluid displaced and the motor RPM. Accuracy and resolution of the motor RPM is critical, so choose a pump drive within your determined tolerance for dispensing.
|Masterflex® Gravimetric Filling System measures to the last drop for high accuracy|
However, this is still a theoretical determination and may not reflect the actual system flow rate. Many factors such as part wear, back pressure (such as from filters or bag fill), fluid friction, and viscosity can affect flow rate and therefore dispensing accuracy. The discrepancy between the theoretical flow rate and the actual is usually minimal and within the acceptable limits of many labs and process floors. If the application is extremely sensitive to dosage, such as the direct value of pharmaceutical biologics and mining slurries or the sensitivity of cell cultures and agricultural crops to additives in the feed, added assurance of accuracy is extremely important. Knowing the exact amount dispensed— and in real time—reduces product waste and produces cost savings.
Generally, there are two methods of measurement: gravimetric and volumetric. The former is the measurement of the product by weight and involves a balance. The latter is by the volume of the liquid dispensed which involves a flow sensor placed downstream from the pump. Each has its own benefits particular to the application.
|Masterflex® Volumetric Filling System provides automatic pump control as the tubing ages.|
Watch the Masterflex Gravimetric System deliver accuracy to the last drop
Masterflex® offers both gravimetric and volumetric dosing equipment consisting of three components: pump system, sensor, and controller, the pump systems have been designed with features that make it easy to integrate into your fluidics system.
If you are concerned about extra drops into your end product or container, here are some quick solutions:
If your application requires a different pump technology, the Masterflex drives with Quattroflow™ pump heads, Masterflex piston pumps, and Masterflex gear pump are all compatible and enhanced by the robust variety of Masterflex tubing formulations so the systems can be used in almost any dosing or metering application.