Electronic apparatus for dispensing precise small quantities of fluid

摘要

An apparatus for dispensing a measured quantity of a liquid has a container holding a quantity of liquid to be measured and dispensed and a conduit with an inlet end, an outlet end and a measuring section having a known volume. A sensor determines when the measuring section contains liquid. A passage with a first valve is provided for delivering liquid from the container to the conduit inlet end and air under pressure urges liquid from the container to the conduit. A source of air under pressure is connected to the conduit and a second valve controls delivery of air to the conduit from the source. A control connected to the sensor and to the first and second valves sequentially closes the second valve and opens the first valve to cause flow of liquid from the container to the conduit until the sensor determines that the measuring section contains liquid, and then closes the first valve and opens the second valve to admit air to the conduit, thereby expelling a measured quantity of liquid from the outlet end.