Patent ID: 6561207
Filing Date: 2003-05-13
Classification: G05D,Y10T

Abstract:
A method for calibrating a flow meter; said flow meter comprising an inlet with a diameter and an outlet with a diameter; a flow restrictor having a restriction chamber and a pressure balancing system interposed between the inlet and outlet; the restriction chamber having a variable orifice assembly; a cylindrical restriction wall with a diameter less than the diameters of the inlet and outlet; and, a pressure sensor and a temperature sensor upstream from the flow restrictor providing input to a meter circuit having calibration data; whereby the meter circuit generates a flow output signal based on the calibration data and the input from the pressure sensor and temperature sensor; the steps of said method comprising:connecting the flow meter to a referenced flow standard; applying a negative gauge pressure to the outlet; setting a zero point on the meter circuit; applying pressure upstream of the meter; measuring a flow; entering a gas specific constant into the calibration data of the meter circuit; obtaining a maximum flow range by adjusting the variable orifice assembly for a given inlet pressure; decreasing the flow to ten percent of maximum flow; measuring the pressure and temperature and storing results in the meter circuit; increasing the flow by ten percent increments up to the maximum flow; measuring the pressure and temperature at each ten percent increment and storing the results in the meter circuit; calculating a slope of a graph of pressure versus mass flow rate from the results stored in the meter circuit; setting the meter circuit by using the slope.