Abstract: A measuring instrument includes a transducer for measuring the depth of water or other value and a transducer for measuring a physical parameter that causes interference error. A calibration polynomial is used to correct the output signal for interference or nonlinearity. The calibration polynomial includes the signal generated by the transducers as independent variables and the output signal as the dependent variable. The calibration polynomial is formed by a correction polynomial having at least one primary measurement signal and at least a first interference related signal as independent variables and a calibrated signal as a dependent variable. To form the calibration polynomial, a preliminary calibration polynomial including the primary independent variable and at least one interference related independent variable is developed.

Abstract: To perform density gradient separation, density gradient columns are prepared at a central location and frozen. They are then taken to other locations while frozen and heated to return the mobility of the density gradient solutions. In this manner, the density gradient solutions can be preserved during travel and for a long period of time, thus removing the need for forming the density gradient solutions at the sites they are to be used and at the time of use and avoiding the need for the purchase of specialized gradient forming equipment in some facilities that use solvent gradient density separations.