38 research outputs found
Vapor pressure measurements over supercooled water in the temperature range from −10 1 °C to +10 −2 °C
An accurate measurement of saturation vapor pressure of supercooled water is a strong challenge in
metrology, mainly due to difficulties concerning keeping water at a liquid state at temperatures well
below the melting point; thus few experimental data covering limited temperature ranges (down to
about 253 K) are reported in literature. For this reason, an investigation of the water vapor – supercooled
water equilibrium along the saturation line is carried out at Istituto Nazionale di Ricerca Metrologica
(INRIM).
Measurements cover the temperature range from 261.26 K to 273.25 K, corresponding to a saturation
vapor pressure from about 244 Pa to 611 Pa. The experimental apparatus includes a borosilicate glass
sample cell, kept in a liquid bath at a constant temperature with millikelvin stability and connected to
a manifold where the pressure is measured using a capacitive diaphragm pressure gauge.
In this work, the water sample preparation, the measuring method and measurement corrections are
reported; moreover, a comparison between experimental and literature data is conducted along with
the most used vapor pressure formulations. Measurement results are discussed and uncertainty sources
estimated. The resulting expanded relative uncertainty (k = 2) varies from 0.085% at 261.26 K to 0.039% at
273.25 K
Whispering Gallery Mode Resonators for Precision Temperature Metrology Applications
In this work, the authors exploited the whispering gallery mode (WGM) resonator properties as a thermometer. The sensor is made of a cylindrical sapphire microwave resonator in the center of a gold-plated copper cavity. Two coaxial cables act as antennas and excite the WGM standing waves in the cylindrical sapphire at selected resonance frequencies in the microwave range. The system affords a high quality factor that enables temperature measurements with a resolution better than 15 mu K and a measurement standard uncertainty of 1.2 mK, a value approximately three times better than that achieved in previous works. The developed sensor could be a promising alternative to platinum resistance thermometers, both as a transfer standard in industrial applications and as an interpolating instrument for the dissemination of the kelvin
Application of plate heat exchangers to the development of portable high-pressure humid gas generators
Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.The preliminary design and testing of a portable, high-pressure humidity generator based on a corrugated-plate heat exchanger (PHE) is described. It resulted in a very simple system, consisting of a bubbling pre-saturator followed by the PHE used as a condenser. The PHE does not need to be hosted in a liquid bath, resulting in a very compact design whose operation is largely independent from a specific bath - which may be available on site – used to condition the temperature of a circulating counter-flow fluid. Experimental tests were performed on a prototype in order to demonstrate the principle and validate at an early stage the system operation. The efficiency of the PHE as condenser was assessed over a temperature range from 0 °C to 65 °C by varying input and influence parameters, such as the dew point temperature, the gas flow rate and its pressure up to 0.5 MPa. The saturation temperature of the humid gas flow compared favourably with the dew-point temperature as measured by a chilled-mirror hygrometer calibrated against a primary humidity standard. The temperature deviations were below 0.02 °C, with a maximum deviation of 0.04 °C, over the whole range of investigated temperatures and pressures.cf201
Development and preliminary investigation of a modular chamber for calibration of relative humidity instruments
In the scope of the project HUMEA – Expansion of European research capabilities
in humidity measurement within the EURAMET EMPIR program, the modular chamber for
calibration of relative humidity instruments was designed, manufactured and characterized.
The modular chamber consists of arbitrary numbers of aluminum blocks each of which
provides accommodation for the one relative humidity probe and also has the fittings for
pressure and temperature probes as well as ports for gas sampling and/or supplying. The gas
can be supplied from the dew/frost point generator or the larger climatic chamber. In the latter
case, the airflow through the chamber can be enhanced by using an additional fan. The
preliminary study was carried out to investigate the improvement in temperature uniformity
using a new chamber in combination with two climatic chambers. The investigation results
show significant improvement in temperature uniformity thus lowering the uncertainties of the
calibration of relative humidity instruments
Improving emerging European NMIs’ capabilities in humidity measurement
The control and measurement of humidity is important for many industrial
applications and to ensure the appropriate storage of materials and products. Humidity
measurement techniques are diverse and each presents different challenges for use and
calibration for a range of pressures and gases. Over the past few years, the development of
humidity sensors and apparatus has matured to a level where traceable calibration is beneficial
to all industries in which humidity and moisture measurement and control are important. This
paper deals with a European project in which the overall objective is to develop or extend the
measurement and research capabilities of the participating emerging NMI/DIs’ countries in the
field of humidity measurements, where access to these types of facilities is currently limited
Progetto e realizzazione di un termometro di riferimento smart per applicazioni farmaceutiche e industriali
Providing measurement traceability to wireless sensor networks in museum applications
The paper presents a preliminary study performed at the Museum of the Cinema in
Torino in order to provide in situ traceability to temperature and humidity wireless sensors.
The experimental activities concerned the development of a suitable on site calibration
procedure and, subsequently, the calibrations of selected wireless sensors which
were belonging to the monitoring and AC control loop network. The work proved to be useful for a validation of the measurement probes as well as for an analysis of different approaches to provide traceability to temperature and humidity sensor networks
Studio e caratterizzazione di sensori polimerici capacitivi per la misura di umidità relativa.
Low-cost Ratiometric Front-end for Industrial PRT Applications
Cost, size, speed, and measurement range limitations make the resistance bridge not always suitable for temperature measurements with platinum resistance thermometers (PRTs) in industrial applications. However, high-accuracy resistance thermometer systems are often needed in many industrial applications, where measurement performances comparable to resistance bridges are often needed at a lower cost and size. A tiny, portable, ratiometric front-end exploiting a 24-bit analog-to-digital converter (ADC) with Σ Δ modulator is described. It was designed to measure the resistance ratio between a 100 Ω industrial PRT (IPRT) and a reference resistor with repeatability to within a few parts in 106. Its small size makes it ideal for integration in the stem-handle assembly of a thermometric probe, enabling an early transmission of measurement data in digital form. The ADC-based system design, development, and performance testing are discussed. The system was investigated in the resistance ratio range from about 4 × 10-3 to 5 × 10-2. Furthermore, a comparison between the system performance and a commercial AC resistance bridge was carried out and the results reported in this paper. An accurate thermometer for industrial applications resulted from the above developments. The compactness of the devices enabled an implementation of the `smart sensor' concept in the measurement chain, where the front-end electronics was placed inside the IPRT handle together with an integrated memory to hold device identification, calibration coefficients, and the associated uncertainty. All data are transmitted to the readout module and are available to the user at a 5 Hz update rate for further analysis