Two-wire transmitters are described in which the required voltage that a control room must supply to the transmitter is lower at high current than at low current, thus freeing up more voltage for other uses, and in which a constant set of operating voltages may be maintained. A corrected pressure in a vortex flow meter may be determined that reflects the mass flow rate. Thus, the mass flow rate may be determined based on the corrected pressure reading and a measured volumetric flow rate. Density may be determined from pressure and temperature using a table containing error values based on a standard density determination and a relatively simple approximation. During operation of a flow meter, the stored error values may be linearly interpolated and the approximation may be computed to determine the density from the stored error value.