WMS measures the electrical current flowing through the small space between two wires by applying electrical voltages over these wires. If steam exists in the small space between them, electricity will have difficulty flowing, resulting in a lower current. For example, the current is low between the red and green wires in (a); however, it is high between the green and blue wires. To enhance the measuring technology for application to two-phase flow under high-pressure and -temperature conditions, materials with high temperature endurances and electrical insulation were adopted for the setting of the wires during manufacture of the test apparatus.