Differential pressure type flowmeter and differential pressure type flowmeter controller

A cost reduction can be achieved by making a differential pressure type flowmeter simple in structure, and highly accurate flow rate measurements can be attained over the wide flow rate range of 100%-1 % with errors E of less than 1 (%SP) both in real time and in a state of inline. To achieve the ends, a differential pressure type flowmeter comprises an orifice, a detector to detect a fluid pressure P 1 on the upstream side of an orifice, a detector to detect a fluid pressure P 2 on the downstream side of an orifice, a detector to detect a fluid temperature T on the upstream side of an orifice, and a control computation circuit to compute a fluid's flow rate Q passing through an orifice by using the pressure P 1 , pressure P 2 and temperature T detected with the aforementioned detectors, and the aforementioned fluid's flow rate Q is computed with the equation Q=C1 · P1/ˆšT· ((P 2 /P 1 ) m - (P 2 /P 1 ) n ) ½ (where C 1 is a proportional constant, and m and n are constants).