Answer: variometer

AnswerCrossword Clue
variometerAn inductor whose total inductance can be varied by altering the relative position of two coaxial coils connected in series, or by permeability tuning, and so can be used to tune an electric circuit
variometerAn instrument for measuring variations in the intensity of the earth's magnetic field
variometeran instrument for measuring variations in magnetic force
variometerA device for indicating an aircraft's rate of climb or descent