PURPOSE: To increase an electric resistance value, improve oxidation resistance and mechanical strength, and use metal such as copper and iron by using a glass-coated extremely thin conductor as an electric resistor.

CONSTITUTION: An end part of an extremely thin copper wire 31 with an about 2μm wire diameter is soldered by removing the glass coating 32, and the external diameter of the glass coating 32 is about 22μm. The electric resistance value of the extremely thin copper wire 31 is 5,380Ω/m at room temperature of 20°C, and its electric resistance temperature coefficient is +3,900PPM/°C. No pinhole in the glass coating 32 is found by a test based upon C3203 of JIS and its breakdown voltage is 2.5kV. The mechanical characteristics of this glass-coated extremely thin copper wire 3, i.e. tensile strength, cutting load, and safety radius of flection are 45kg/mm2, 24g, and 1.5mm respectively. Two posts 2 use nickel wires with a 1mm diameter and are at a 4mm center-to-center interval, and a DC power source, variable resistance, etc., are connected to both posts 2.