A method of making a spark plug having a noble metal chip joined to an electrode main body of a ground electrode by interposing therebetween an intermediate member. The polarization nulling can be performed using a heuristic multipoint extrema search method, such as Nelder-Mead method. A gantry positioned on the frame permits easy movement of individual modules into position. A method of separating nanoparticles of a desired size employs an array of bowl-shaped structures. The coolant flows into the flow passage through the inflow nozzles. A second compensation value is derived from a plurality of difference values.