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A brief analysis of modern methods for measuring impedance parameters and error sources that limit their accuracy in a wide range of frequencies is given. An effective way is substantiated to solve the main problem-a significant increase in the errors of the separation of the information signal into quadrature components with increasing frequency. The schemes of construction of the broadband single-phase and multi-phase digital generators of test and reference signals using Johnson's ring counter, which have very small phase errors, as well as the control scheme of the phase ratio of the testing and reference signals are detail considered in the article. The considered structures and principles of operation of the impedance meters with the use of impedance-voltage transformation, of the bridge method with balancing by module and phase of the imbalance signal and their combinations have been developed on their basis.

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Аннотация. Рассматриваются источники, даются теоретическая и экспериментальная оценка погрешностей, возникающих из-за неполного подавления синфазной помехи на дифференциальном сенсоре. Предложена усовершенствованная схема измерительного канала, исследована ее функция преобразования, показана возможность диагностики датчиков. На векторных моделях оценено подавление синфазных помех при разных параметрах пар преобразователей. Получено экспериментальное подтверждение теоретических оценок возможных уровней погрешностей от синфазных помех в исследованных измерительных каналах. Ключевые слова: кондуктометрический биосенсор, дифференциальный датчик, подавление помех

The structure and construction of the unified basic measuring module for creation of the broadband means for impedance measurement are described, which was used by us to study the important metrological characteristics of the test and reference signals digital generators for such devices. The sources and the magnitudes of the modular and phase errors are determined for the measuring channels with direct conversion of the impedance parameters and with compensation of the phase shift of the signal in the measurement object, as well as for the channels with balancing the measuring circuit modulo and phase. The researches shown attainability of measurement errors of an object impedance on absolute value and on its phase angle tangent less than 0.1% at frequencies up to 1 MHz. At the frequency of 1 kHz, the measurement error on the quadrature parameter did not exceed 0.001%. The study of the two-phase generators with precise adjustment of phase difference of reference and test signals showed the ability to achieve the time errors of their formation no more than a few nanoseconds.