A three-piece pressure sensor assembly includes a one-piece pressure port formed of cold rolled steel, a stainless steel sensor element having an elongated annular side-wall, and an O-ring. The present invention includes starting the operation of a motor including windings and a rotor; placing the motor in a first operational state; driving the motor from the first operational state to a second operational state; and sensing a variation in an electrical waveform induced by driving of the motor to determine a cycle period from which the speed of the motor can be determined. The oscillator, configured in the form of an H, includes a support, two first arms and two second arms. An elasticity modulus of the core is larger than an elasticity modulus of the under cladding layer and the over cladding layer. At least one of the cam followers remains engaged in a corresponding cam groove while at least one of the other of the cam followers comes out of the end opening and is disengaged therefrom when the linearly movable frame moves to movement limit in the optical-axis direction. When the method is used, evaporation of sodium is suppressed and thus a beta alumina solid electrolyte having a high density, a low porosity, and a composition that is near a desired composition is produced.