An electrostatic sensor device including a first sensor element and a second sensor element; a dielectric substrate material formed in two layers, and a sensing hole which penetrates the dielectric substrate material from its upper surface to its lower surface. The first sensor element is receivable in the sensing hole; and second sensor element includes a first conducting ring disposed on an upper surface of said dielectric substrate and surrounding said sensing hole. The second conducting ring is disposed on a lower surface of the dielectric substrate and surrounds the sensing hole. The first sensor element and the second sensor are capable of producing a variable response when the first sensor element is disposed in the sensing hole.