Nuclear Quadrupole Resonance (NQR) spectroscopy has been known for 70 years. It is suitable for the study of measured (poly)crystalline chemical compounds containing quadrupole nuclei (nuclei with spin I ≥ 1) where the characteristic NQR frequencies represent the fingerprints of these compounds. In several cases, ¹⁴N NQR can distinguish between the polymorphic crystalline phases of active pharmaceutical ingredients (APIs). In order to further stimulate ¹⁴N NQR studies, we review here several results of API polymorphism studies obtained in Ljubljana laboratories: (a) In sulfanilamide, a clear distinction between three known polymorphs (α, β, γ) was demonstrated. (b) In famotidine, the full spectra of all seven different nitrogen positions were measured; two polymorphs were distinguished. (c) In piroxicam, the ¹⁴N NQR data helped in confirming the new polymorphic form V. (d) The compaction pressure in the tablet production of paracetamol, which is connected with linewidth change, can be used to distinguish between producers of paracetamol. We established that paracetamol in the tablets of six different manufacturers can be identified by ¹⁴N NQR linewidth. (e) Finally, in order to get an extremely sensitive ¹⁴N NQR spectrometer, the optical detection of the ¹⁴N NQR signal is mentioned.

The object of the proposed paper is to design and analyze the performance of a non-contact heart rate variability (HRV) measuring device based on ultrasound transducers. The rationale behind non-contact HRV measurement is the goal of obtaining a means of long term monitoring of a patient’s heart performance. Due to its complexity as a non-contact measuring device, influential physical quantities, error source and other perturbations were thoroughly investigated. For medical purposes it is of utmost importance to define the target uncertainty of a measuring method from the side of physicians, while it is the role of scientists to realistically evaluate all uncertainty contributions. Within this paper we present a novelty method of non-contact HRV measurement based on ultrasound transducers operating at two frequencies simultaneously. We report laboratory results and clinical evaluations are given for healthy subjects as well as patients with known heart conditions. Furthermore, laboratory tests were conducted on subjects during a relaxation period, and after 1 min physical activity

The paper presents a novel measuring system for detecting air gap anomalies in direct-drive electrical motors. The air gap anomalies can be of different types of eccentricity which may in extreme cases result in a mechanical rub between the stator and rotor, potentially leading to a motor breakdown. A novel measuring method is proposed using a sensory system integrated in a motor air gap to measure its width directly either in a static or dynamic state. It uses an optical sensory system to measure reflection of the infrared radiation between the rotor and stator. The method is validated by using a parallel measuring system employing an analogue Hall sensory system that measures the change in the magnetic-flux density. The two measuring systems are calibrated by comparing them to a reference laboratory measuring system consisting of a camera and lenses. The calibration is performed in a laboratory in a motor static state within one mechanical rotation cycle of the rotor. Using different calibration techniques, the optimal system accuracy, with a maximum permissible error of 0.15 mm is obtained, in the measuring range between 0 mm and 2 mm. It covers most applications of the direct-drive electrical motors. The new measuring method is validated by using an experimental set-up consisting of the presented optical sensory system and validation system an analogue Hall integrated on a testing platform (Smart Fortwo car).

When designing a single tube practical acoustic thermometer (PAT), certain considerations should be addressed for optimal performance. This paper is concerned with the main issues involved in building a reliable PAT. It has to be emphasised that a PAT measures the ratio of the time delay between the single temperature calibration point (ice point) and any other temperature. Here, we present different models of the speed of sound in tubes, including the effects of real gases and an error analysis of the most accurate model with a Monte Carlo simulation. Additionally, we introduce the problem of acoustic signal overlap and some possible solutions, one of which is acoustic signal cancellation, which aims to eliminate the unwanted parts of an acoustic signal, and another is to optimize the tube length for the parameters of the gas used and specific temperature range.

This article presents a Johnson noise thermometer with a signal acquisition system based on a sound card. The thermometer uses a simple analogue circuit to measure the Johnson noise on a resistor. No external hardware or power supply is necessary, except for a reference multimeter. Data processing is performed in real time on a personal computer using LabView software. The results show that the developed thermometer has an expanded uncertainty (k = 2) of 0.8 ℃ over a temperature range from − 196 ℃ to 300 ℃, with a measurement time of 5 min.

There is a worldwide need to improve blood pressure (BP) measurement error in order to correctly diagnose hypertension. Cardiovascular diseases cause 17.9 million deaths annually and are a substantial monetary strain on healthcare. The current measurement uncertainty of 3 mmHg should be improved upon. Dynamic pressure measurement standards are lacking or non-existing. In this study we propose a novel method of measuring air pressure inside the sphygmomanometer tubing during BP measurement using a condenser microphone. We designed, built, and tested a system that uses a radiofrequency (RF) modulation method to convert changes in capacitance of a condenser microphone into pressure signals. We tested the RF microphone with a low-frequency (LF) sound source, BP simulator and using a piezoresistive pressure sensor as a reference. Necessary tests were conducted to assess the uncertainty budget of the system. The RF microphone prototype has a working frequency range from 0.5 Hz to 280 Hz in the pressure range from 0 to 300 mmHg. The total expanded uncertainty (k = 2, p = 95.5%) of the RF microphone was 4.32 mmHg. The proposed method could establish traceability of BP measuring devices to acoustic standards described in IEC 61094-2 and could also be used in forming dynamic BP standards.