Time of Flight Sensor with a Flow Parallel Wire
A time of flight sensor has been equipped with a sensing wire parallel to the flow direction (flow parallel wire, FPW). A heat pulse is generated with a coil in the flow channel. The FPW has a center tap allowing its upstream and downstream parts to join in a half bridge. When a heat pulse passes the FPW, a large output peak is generated. The time between heat pulse generation and recording the peak maximum is only marginally affected by the properties of the fluid. With a combination of two FPWs, a measuring range of approximately 0.01–0.5 m/s can be achieved.
Thermal flow sensor for liquids and gases
A new type of a flow sensor is presented which is based on a thermal principle. The combination of two detecting methods results both in a considerable increase in measuring range (0.1 to 150 mm/s) and in a shorter reaction time of less than 2 ms. Furthermore, the sensor is furthermore relatively insensitive to pollution. Devices were manufactured and successfully tested for liquids and gases.
Miniaturized flow sensor with planar integrated sensor structures on semicircular surface channels
A calorimetric miniaturized flow sensor was realized with a linear sensor response measured for DI water flow from 40 nlmin-1 up to 300 nlmin-1. A versatile technological concept is used to realize a sensor with thermally-isolated freely-suspended silicon-nitride microchannels directly below the substrate surface. The microchannel concept allows for the planar integration of sensor structures in close proximity to the fluid. Chemical-resistant fluidic connections can be made directly on top of the microchannels, without introducing large dead-volumes. The realized flow sensor consists of a microchannel with low hydraulic resistance and small total fluid volume.