Abstract. Comparators capable of comparing two alternating signals of the similar frequency within a wide dynamic range of frequencies and voltages are lock-in amplifiers with a differential input. The paper presents the methods and means are suggested for reducing the measurements uncertainty conditioned by the finite value of the common-mode rejection ratio in lock-in amplifier with a differential input.
The paper presents the instrument for measurement of transfer ratio voltage transformers in the frequency range. The instrument distinctive feature is measuring of small differential signal of the voltages with sensitivity 2 nV against the background of large common-mode signal. The instrument features, its technical and metrological parameters are also considered.
The mode of primary oscillations of a micromechanical gyroscope (MMG) sensor is provided by an electrostatic comb-drive actuator in which the interaction between the micromechanical structures and electronics occurs by means of a single or differential capacitive sensor. Two pairs of capacitive sensors are traditionally used for frequency stabilization of MMG primary oscillations. The first pair of capacitive sensors excites primary oscillations, while the second measures the amplitude of primary oscillations. The stabilization system provides a continuous frequency tuning of primary oscillations that increases the duration of transition processes, the time of operational readiness, and the instability of the output signal from the secondary oscillation channel of the MMGs. This paper presents a new approach to the primary oscillation control system of the two-component MMG. The method of calculating the natural resonant frequency is based on measurements of the total current passing through the comb-driver actuator capacitances, and a lock-in detection is suggested. This paper consists of the results of the numerical analysis, the description of the proposed approach to the frequency control of the primary MMG oscillations, and the Simulink model of the behaviour of the MMG stabilization system, depending on its mechanical-and-physical properties with regard to a 2% shift of the natural resonant frequency. The frequency control of the primary oscillations at 2% frequency detuning is performed within 0.11 s.
Transducers of current to voltage, such as current shunts are widely used in control systems for the mechanical engineering. The shunt is required to determine the value of its resistance on DC and AC currents to determine the transfer ratio error in the wide frequency band in process of verification or calibration. Well-known methods for resistance measuring (by Thompson' double bridge; magnetic comparator, compensation technique, etc.) require a commerce resistance and difficult to implement for shunts with resistance less than 0.1 Ohms. The paper describes a procedure for measuring the complex impedance of transfer ratio of current shunts in the frequency band using the lock-in amplifier with the differential input. The experimental results of the proposed procedure for coaxial shunt with nominal resistance at DC 750 uOhm and 160 uOhm are described.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.