Abstract: The real flow calibration cost of large diameter electromagnetic flowmeter is very high, in order to solve the problem, a new low cost calibration method is presented, which take small tube as unit element. It divides the flowmeter measurement zone into several axial subspace based on element theory, the induction electromagnetic force of each subspace was measured with a small measure tube, and the effective information of characteristic is extracted , then the characteristics distribution of flow meter is reconstructed with them, it effectively solves the high cost of real flow calibration, which provides an effective method for the low cost calibration of large diameter electromagnetic flowmeter. The induced electromotive force under zero drift, and the relationship between device coefficient and instrument coefficient of small measurement tube are focus discussed, and the final expression of calibration coefficient was given. A large diameter electromagnetic flowmeter was calibrated with actual flow calibration and unit element calibration, respectively. Experimental results indicate that the new calibrating method is available, and the accuracy grade is 0.5.

Key words: Electromagnetic flowmeter, Large diameter, Low cost calibration, Unit element