Abstract: A method of making an electrophoresis medium having a predetermined gradient in concentrations of an acrylamide compound and a cross-linking agent comprises the steps of mixing two kinds of aqueous solutions containing the acrylamide compound and the cross-linking agent in different concentrations such that a mixing ratio of the aqueous solutions to each other is changed gradually, thereby to form a predetermined gradual change (gradient) in concentrations of the acrylamide compound and the cross-linking agent in the mixture, and carrying out cross-linking polymerization of the mixture in the presence of a polymerization initiator. Viscosity values of the two kinds of the aqueous solutions containing the acrylamide compound and the cross-linking agent in different concentrations prior to the mixing are adjusted to be substantially equal to each other.

Abstract: The pressure response of a pressure control valve is adjusted by a solenoid valve of which the solenoid is connected to an electrical three point control device. A programmed signal and an actual signal derived from a transformer of the control pressure valve are fed to the input of the three point control device.