Flowmeters get small and fast

Engineers at Yamatakes Sensing Control Ltd., Santa Clara, Calif., have downsized the traditional thermal flow meter to give it quicker response and more accurate readings. It uses the same principles as traditional sensors -- upstream and downstream temperature probes on a capillary with a heater in between -- micromachined on a chip. The heater warms the fluid or gas and creates a temperature difference. This difference, as measured by the sensor, is used to calculate density and flow rate of the material. The thermal sensor has relatively little mass, giving it quick response times and more resolution. Engineers currently do not have a version that handles corrosive liquids and gases, but they can measure flow in air, nitrogen, argon, oxygen, carbon dioxide, methane, propane, helium, and a host of other gases.