Plates made of aluminum and tungsten alloy are used to cover a temperature range of up to 250°C and 600°C, respectively. Each plate, the guard ring and the furnace are connected to a separate control system and stabilized power supply, ensuring fast attainment of programmed plate temperatures and perfect stability. In equilibrium, differences between the programmed and actual plate temperatures are ≤ 0.01 K for the hot plate and the guard ring.