Patent ID: 7971480

Claim:
A mass flow controller thermal sensor comprising: a capillary tube having an upstream tube portion, a tube bend portion, and a downstream tube portion, wherein, the upstream tube portion comprises an upstream portion length, the downstream tube portion comprises a downstream portion length, the downstream portion length is substantially equal to the upstream portion length and the downstream tube portion is substantially parallel to the upstream tube portion, a first pair of thermal sensing elements coupled to the upstream tube portion, the first pair of thermal sensing elements including a first upstream element and a first downstream element; a second pair of thermal sensing elements coupled to the downstream tube portion, the second pair of thermal sensing elements including a second upstream element and a second downstream element the second pair of sensing elements generally opposing the first pair of sensing elements; a thermally conductive element coupled to the capillary tube at a location between the first downstream element and the second upstream element, and the thermally conductive component is disposed to thermally couple the capillary tube to an ambient temperature; and the first and second pairs of thermal sensing elements being coupled to form a bridge that includes a top node, a right node, a bottom node, and a left node, and the first upstream element is coupled between the left and bottom nodes, the first downstream element is coupled between the left and top nodes, the second upstream element is coupled between the top and right nodes, and the second downstream element is coupled between the right and bottom nodes.