The authors present a model of the respiratory system in forced expiration as an answer to the unknown pressure pulse excitation. The model has the form of a voltage divider circuit, where gas flow volume velocity is the current reaction (or the volume is the voltage reaction). The analysis is presented in time domain. The model’s finding is realized in two main stages. In the first stage an RCL net is built. On the basis of this structure the exciting signal is found in the form that the answer to the model is V(t) (or Q(t)), very similar to the real object’s answer, in the minimum mean-square-criterion.

A mini TPW system was introduced as an excellent way to measure the errors in the calibration system of a secondary level temperature laboratory. In this paper, the structure and operation of this system is briefly introduced. Also, its performance is discussed. The mini TPW system was directly compared to a traditional TPW cell. The difference between the mini TPW system and the traditional TPW cell was found to be less than 0.3 mK using an SPRT. The expanded (k = 2) uncertainty of the mini TPW system is better than 0.5 mK. Several thermometers with different structures were tested in the system. Errors seen with the different thermometers between the mini TPW system and the traditional TPW system are reported.

This work deals with the dynamic thermal conductivity (λ) measurements by hot wire method. This measurements are performed at unstationary state conditions (short time). Very thin (0.05 mm) manganin wire is supplied by DC electrical power and produces a thermal impulses which pass through the testing sample. Dynamics of this process depends on the type of the sample material. Temperature, electric power and time elapsed during the process are measured parameters from which thermal conductivity could be calculated. Measurement results are compared with those gained by the standard guarded hot plate (stationary) method. Testing samples are made from isotropic and homogenous materials.

A comparison of some defining temperature fixed-points on the ITS-90 was carried out at the National Institute of Standards using four calibrated SPRTs. The comparison was performed using large and small sealed cells from two different sources. The large cells, namely set1 cells and taken as reference cells were realized using the same technique used with the small cells (set2). The main task is to study the set2 cells and the possibility of using them instead of the large size (reference) cells. Measurements showed good results and some agreement between the two sets. The differences between the set2 cells and reference cells set1 were well within 2 mK.

The main purpose of this work is to present the manufacturing, calibration and validation of a system for wet and dry bulb temperature measurements obtained on a new psychrometer.
The calibration has lead to the adjustment of the appropriate psychrometer coefficient for the developed psychrometer, as a function of the wet bulb temperature, which fits best with experimental data, obtained on the range from 34% to 87% RH and 15°C to 30°C. Another set of experimental points on this range was used for evaluation of the psychrometer uncertainty.
An electronic hygrometer was calibrated simultaneously, and its calibration was also evaluated. The uncertainty of the Relative Humidity obtained in the calibration of the psychrometer was found to be only slightly higher than the uncertainty for the electronic hygrometer. For the wet-bulb temperature determination, the hygrometer presents itself as more precise, while the psychrometer was more accurate. Either could be used for technological development of the humidifier, but the psychrometer delivers a direct measurement of the wet-bulb temperature, independent of the local pressure and dry-bulb temperature, which affects the calculation obtained from the hygrometer data.