Capabilities of a New Pressure Controller for Gas-Controlled Heat Pipes

Pressure control is used in many metrological applications and for the control of thermodynamic quantities. At the Italian National Research Institute of Metrology (INRiM) a new pressure controller has been designed and assembled, operating in the pressure range between 4 kPa and 400 kPa. This innovative instrument uses a commercial pressure transducer with a sensitivity of 10 4 and several electro-valves interposed among calibrated volumes with different dimensions in order to realize known ratios for very fine pressure changes. The device is provided with several circuits to drive the electro-valves actions, for the signals processing and transmission, and for both manual and automatic control. Input-output peripherals, such as a 4x20 dot matrix display and a 4x4 keyboard allow to set the parameters and data visualization, while a remote control port allows the interfacing with a computer. The operating principle of this pressure controller has been recently applied, with excellent results, to control the pressure in the Gas Controlled Heat-Pipes by using a Standard Platinum Resistance Thermometer (SPRT) as a temperature/pressure sensor, achieving in this case a relative sensitivity better than 10-6 in pressure. Several tests were made also controlling the pressure by means of a commercial sensor. The device, its main components and capabilities are here reported, together with application tests and results.