The paper deals with a method of THD factor measurement with using watch filtration of the fundamental frequency. The proposed application enables to identify main frequency changes of evaluated signal what improves the effectiveness of filtration. Results of the simulation studies and laboratory experiments proved usefulness of suggested solutions for measurement of THD factor. It let design a prototype of measuring device based on the proposed method.

Modulation quality in most of digitally encoded cellular systems is examined by measuring the phase error and the frequency error of the transmitted signal. Phase error is an indication of how accurately the individual bits modulate the radio-frequency carrier; frequency error is the difference between the specified carrier frequency and the actual carrier frequency.
The paper proposes a new technique for phase and frequency error measurement. The technique is based on a suitable digital signal-processing algorithm, capable also of gaining burst synchronisation on TDMA signals; downconversion and digitisation of the incoming signal are preliminary executed. Exploiting the instantaneous frequency trace related to the analysed burst and performing a nice interpolation of sampled data, the technique assures reliable demodulation along with low uncertainty.
Paying attention to GSM cellular system, the fundamental stages of the digital signal-processing algorithm are first described in detail. Then, the metrological characterisation of the proposed technique is carried out by means of experiments on GSM signals with known characteristics; the obtained results are finally compared to those obtainable by similar techniques already available in literature.

The result of a measurement has uncertain value-band depending on dynamic behaviour of the measured object and measurement instrumentation. Numerical value is attained with successive approximation of the difference between the reference and measured quantity. Estimation of the difference between two levels is possible with at least two sampling pulses. The dynamic error is proportional to that difference with addition of some constant. For effectiveness of differential tracking, the non-uniform quantization must fulfill three conditions: partitions into halves, increasing quantization uncertainty with difference, and low overlapping of the quantization intervals. The best trade between the number of decision levels and the settling time is with pure exponential quantization rule. The fastest response is achievable with base 2. The conversion time can be shortened to one third in comparison with the best parallel-serial A/D conversions.

This paper describes the measurement services, the instrumentation and procedures available for force metrology at the National Institute of Standards and Technology, USA. The uncertainty in the forces realized over a range of 44 N to 53 MN is reviewed. The maintenance and the uncertainty of the voltage ratio indicating system for strain gage load cells are discussed.

The NRLM has therefore developed a force standard machine employing an electromagnetic force compensation sensor to extend the established 10 N to 20 MN force standards to forces of mN order. We are currently conducting research on achieving force standard measurement precision in this range of ± 0.02 % or less. In order to make comparative verification of force standard values established by deadweight-type force standard machines, the rated capacity of the electromagnetic force compensation sensor incorporated in this machine is 50 N at 0.1 mN resolution. However, by reducing the capacity of the electromagnetic force compensation sensor as necessary, the measurement range can be switched to suit the capacity of the force transducer. In this case, however, external vibrations have a major impact on the measurement result.
This report describes the structure of a force standard machine employing an electromagnetic force compensation sensor developed by the NRLM, test force control methods, and performance evaluation results obtained through comparison with a deadweight force standard machine.