At the Italian National Research Institute of Metrology the activities and studies on the Gas Controlled Heat Pipes are constantly increasing in terms of involved personnel, instrumentations and devices available. In last two years, among the other activities, a totally new Gas-Controlled Heat Pipe operating with mercury as working fluid has been designed, manufactured and completely characterised. \ud \ud This Heat Pipe is made in stainless steel and provided with three thermometers wells. A dedicated furnace has been constructed too and specific software algorithms have been implemented for the temperature and pressure control. This device will be used as low temperature reference for the new “Temperature Amplifier” and, at the same time, as calibration facility for thermometers calibrations by comparison in the field between 220 °C and 450 °C. All details regarding this Heat Pipe, including assembly, filling and testing procedures, and the complete characterisation campaign are here summarised. \ud \ud Results in terms of temperature stability, uniformity, time response are reported, and demonstrate the capabilities of this Gas Controlled Heat Pipe to be a useful device for researches and applications in contact thermometry. \ud \ud A further Gas Controlled Heat Pipe operating with mercury has been manufactured, provided with six thermometer wells and will be characterised for the contact thermometry calibration laboratory on INRiM and for other calibration groups; this device is presented too
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. \ud 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. \ud 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
A temperature reference system for calibrating fluorescence-based sensors was developed. The system is based on a special thermostatic chamber and on an electro-optic system equipped with a fiber-optic scanner. A thin layer of the sensing material to be calibrated can be coated onto a temperature-controlled reference surface, which is housed inside the thermostatic chamber. It was designed in such a way as to operate under different conditions (from vacuum to atmospheric pressure) in order to evaluate the effect of the surrounding fluid on the surface temperature measurements. The reference surface can be heated both radially, by a wire-wound heater, and axially, by a thermoelectric cooler. Experimental investigations were carried out in the temperature range -50 °C to about 200 °C. The results showed a temperature stability of better than 0.03 °C and a surface temperature uniformity within 0.02 °C. The system was used to characterize a sensitive phosphor. The phosphor calibration curve was thus obtained, with a single-point repeatability of better than 0.1 °C. The spatial temperature uniformity of the phosphor-coated surface was also investigated by using the built-in fiber-optic scanner in both environments. The results showed a temperature uniformity within 0.1 °C.
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