Flow sensor assembly

A flow sensor assembly is disclosed comprising flow sensing channel regions with different cross-sectional areas for optimum performance with different flow ranges. The flow sensor assembly comprises a flow inlet channel 1; a flow outlet channel 2; a flow sensing channel 3a, 3b, 3c through the flow sensor assembly located between the flow inlet channel 1 and the flow outlet channel 2; one or more substrates; and one or more dielectric layers each located on a first side of a substrate. The flow sensing channel comprises at least two flow sensing channel regions 3a, 3b, 3c. A first flow sensing channel region 3a has a first cross-sectional area and a second flow sensing region 3b has a second cross-sectional area different from the first cross-sectional area. The flow sensor assembly has at least two flow sensing elements 4a, 4b, 4c each located on or embedded within a dielectric layer. A first flow sensing element 4a is configured to sense fluid flow in the first flow sensing channel region 3a and a second flow sensing element 4b is configured to sense a fluid flow property in the second flow sensing channel region 3b. The sensor assembly may be a MEMS thermal flow sensor. The sensing elements may be resistive hot wires. The flow channel regions may be in series fig. 1 or parallel fig. 3.