Fluid dispensing systems typically deliver quantities of fluid via tubing or pipes to one or more components within the system. In certain fields, fluid dispensing systems may deliver small quantities of fluid. For example, in the medical field, a fluid dispensing system may deliver small quantities of fluid into a patient's vascular system. In other fields, fluid dispensing systems may deliver larger quantities of fluid. For example, in a large-scale hotel, laundry or restaurant facility, a fluid dispensing system may deliver large quantities of detergent, rinse agent, bleach or other cleaning agents via tubing to a large number of commercial dishwashing or laundry machines on a continual or periodic basis.
A fluid dispensing system may include a pump and a product reservoir. The pump draws fluid from the product reservoir and delivers it to another component within the system via tubing. Many different forms of pumps may be used within a fluid dispensing system. In addition, the fluid dispensing system may include multiple different pumps within a pump assembly, or within multiple pump assemblies. Further, the fluid dispensing system may include a controller that controls operation of the one or more pumps within the system.
In medical applications, ultrasonic air or bubble detectors detect bubble or air presence in the blood stream or drip chamber systems to prevent bubble penetration to patient blood. The wavelengths used are generally of the same order as the size of the bubbles to be detected. To detect very small bubbles, high frequency sound of several megahertz (ultrasound) may be used. These devices typically include an ultrasonic piezoelectric transmitter and receiver located on opposite sides of the piping/tubing. Such systems may also include special acoustic lenses to transfer and focus the acoustic energy to the examined area.
These systems use a change in signal amplitude of the received signal as compared to the transmitted signal as the criterion for detection of bubble presence. Generally, the amplitude of the detected signal decreases if bubbles are present or the fluid level is down due to defocusing of acoustic energy.