The paper presents a bilateral comparison for measurement of accelerometer sensitivity in frequency range from 0.1 Hz to 20 kHz between NPL, India and The Modal Shop, USA. Two artefacts were utilized for bilateral comparison, one PCB 353B04 sensor and another for the low frequency, PCB Q353B51 along with ICP sensor signal conditioner. The measurements were conducted in the low frequency range from 0.1 Hz to 100 Hz for the PCB Q353B51, while the PCB 353B04 sensor was used in frequency range 5 Hz to 20 kHz. The results of the bilateral comparison show an E _n value less than 0.5 for both the accelerometers. The comparison of results with PCB calibrated values shows a maximum deviation of 0.7 % at 0.1 Hz, which lies well within the measurement uncertainty stated at low frequencies.

The application of heterodyne interferometry with direct access to the frequency modulated signal was deemed unfeasible for low frequency vibration measurement, because of the trade-off between a carrier frequency and modulation bandwidth in the MHz range calling for high sampling rates on the one hand, and the low vibration frequency calling for long measuring times on the other hand. Data acquisition systems with the necessary amount of sample memory are expensive and the CPU time needed for the appropriate data processing becomes prohibitive at very low vibration frequencies.
PTB recently developed a new method related to the classic homodyne fringe counting, which reduces the sampling rates for the interferometer signal to ranges related to the spectral contents of the vibration motion.
The new method of heterodyne fringe counting is capable of magnitude and phase response measurements. The contribution describes the methodology and discusses some of its distinctive features and possible pitfalls.

The study of posture and movement control in humans requires technological supports able to provide accurate, reproducible and repeatable information on displacement and/or position in real-time.
A methodology used in rehabilitation and in sports medicine involves the use of rocking boards on which the subjects must keep their balance, in different operating conditions. The use of rocking boards combined with displacement and position sensors allocated at specific points of the human body, can provide information on the single stance stability and contribute to reprogramming the postural and proprioceptive control of healthy and pathological subjects (orthopaedic and neurological patients), mitigating the risk of falling in older subjects and decreasing the risk of injuries in sport athletes.
This paper describes the procedure used for the characterization of rocking boards (uniaxial and triaxial) and wearable sensors as postural readers, in terms of angular position. In the first step both measuring systems are characterized by a reference accelerometer, in order to accurately determine the angular positions.
A metrological approach in biomechanical measurements is necessary since it provides more accurate and reproducible data on which evaluations related to human health and wellbeing can be achieved.

Hardness uniformity is the most important property of hardness block and depends on the quality of the starting material, process of obtaining, heat and surface treatment. All parameters must be selected very carefully to achieve homogenous microstructure with no defects. Vickers hardness blocks for the high hardness range were produced by two different processes of powder metallurgy; conventional liquid phase sintering in hydrogen and sinter HIP. Nano powder of WC with a grain size of 150 nm with specific surface area of 2,5 m²/g and addition of grain grow inhibitors was used as staring powder. Hardness uniformity of the produced blocks was investigated in this paper. Surface of the blocks was divided into radial and circumferential divisions forming different sections on the block surface. Hardness measurements were performed in each section with one level of the test force. Applied force was 9.807 N what corresponds to measuring method HV1. For reliable hardness measurement five indentations were measured in each section. Overall 40 indentations were performed based on which conclusions about the hardness uniformity of the Vickers hardness blocks were brought. Hardness uniformity was tested by analysis of variance, ANOVA, for single factor in to order to determine if significant hardness variations across the block surface are present. From carried research was concluded that hardness distribution on test surfaces of Vickers hardness blocks has a trend according to a process of obtaining.

Each recording of measurement values postulates the consistency of the realization and mapping of the measurement scale by the measuring device. The transfer of a measurement scale to a measuring or testing device at two or more data points is done in a linear space. A functional relationship between measurement scale and measured value realization is derived from regression analysis. A differentiation can be made between systematic, random and symmetric deviations between measurement realization and measurement scale. The systematic and symmetric deviations are compensated by using a correction function. All remaining deviations become part of the measurementuncertainty. The functional description of the uncertainty of measurement can be modelled using different models with symmetric and asymmetric limits of the interval.