Vadim M. Agafonov

Molecular electric transducers as motion sensors: A review

This article reviews the development of a new category of motion sensors including linear and angular accelerometers and seismometers based on molecular electronic transducer (MET) technology. This technology utilizes a liquid not only as an inertial mass, but also as one of the main elements in the conversion of mechanical motion into electric current. The amplification process is similar to that in a vacuum triode. Therefore, it is possible to achieve signal amplification close to 108. Motion sensors demonstrating wide frequency and dynamic range and sensitivity that are one to two orders of magnitude better than MEMS devices of the same size have been developed.

A micro seismometer based on molecular electronic transducer technology for planetary exploration

This letter describes an implementation of micromachined seismometer based on molecular electronic transducer (MET) technology. As opposed to a solid inertial mass, MET seismometer senses the movement of liquid electrolyte relative to fixed electrodes. The employment of micro-electro-mechanical systems techniques reduces the internal size of the sensing cell to 1μm and improves the reproducibility of the device. For operating bias of 600 mV, a sensitivity of 809 V/(m/s2) was measured under acceleration of 400μg(g≡9.81m/s2) at 0.32 Hz. A −115 dB (relative to (m/s2)/Hz) noise level at 1 Hz was achieved. This work develops an alternative paradigm of seismic sensing device with small size, high sensitivity, low noise floor, high shock tolerance, and independence of installation angle, which is promising for next generation seismometers for planetary exploration.This letter describes an implementation of micromachined seismometer based on molecular electronic transducer (MET) technology. As opposed to a solid inertial mass, MET seismometer senses the movement of liquid electrolyte relative to fixed electrodes. The employment of micro-electro-mechanical systems techniques reduces the internal size of the sensing cell to 1μm and improves the reproducibility of the device. For operating bias of 600 mV, a sensitivity of 809 V/(m/s2) was measured under acceleration of 400μg(g≡9.81m/s2) at 0.32 Hz. A −115 dB (relative to (m/s2)/Hz) noise level at 1 Hz was achieved. This work develops an alternative paradigm of seismic sensing device with small size, high sensitivity, low noise floor, high shock tolerance, and independence of installation angle, which is promising for next generation seismometers for planetary exploration.

Molecular Electronic Linear Accelerometers. Preliminary Test Results

The paper focuses on the accuracy characteristics of linear motion meters based on molecular electronic technology. Zero bias stability in terms of Allan variance and power spectral density is experimentally determined for the linear accelerometers. Harmonic distortions depending on the input amplitude are measured.

Molecular Electronic Angular Motion Transducer Broad Band Self-Noise

Modern molecular electronic transfer (MET) angular motion sensors combine high technical characteristics with low cost. Self-noise is one of the key characteristics which determine applications for MET sensors. However, until the present there has not been a model describing the sensor noise in the complete operating frequency range. The present work reports the results of an experimental study of the self-noise level of such sensors in the frequency range of 0.01–200 Hz. Based on the experimental data, a theoretical model is developed. According to the model, self-noise is conditioned by thermal hydrodynamic fluctuations of the operating fluid flow in the frequency range of 0.01–2 Hz. At the frequency range of 2–100 Hz, the noise power spectral density has a specific inversely proportional dependence of the power spectral density on the frequency that could be attributed to convective processes. In the high frequency range of 100–200 Hz, the noise is conditioned by the voltage noise of the electronics module input stage operational amplifiers and is heavily reliant to the sensor electrical impedance. The presented results allow a deeper understanding of the molecular electronic sensor noise nature to suggest the ways to reduce it.

Self-Noise of the MET Angular Motion Seismic Sensors

Interest to angular motion seismic sensors is generated by an expectation that direct measurement of the rotations, associated with seismic signals, would allow obtaining more detailed and accurate information from them. Due to the seismic signals low intensity a self-noise of the sensors is one of the most crucial parameters, characterizing their performance. In seismic applications the molecular-electronic transfer (MET) technology is considered as one of the most promising technologies for the rotations measurements. In this research we have developed a noise model for the MET angular sensors. The experimental part of the research which fully agrees with theoretical data includes the instrument self-noise measurement in quite locations. Based on the modelling we have revealed the directions of further research to improve the MET angular sensors performance.

Operating principles and technical characteristics of a small-sized molecular-electronic seismic sensor with negative feedback

The results of analysis of the output parameters of small-sized seismic motion sensors based on molecular electronics are presented. These devices feature a molecular-electronic transducer with negative feedback the introduction of which makes it possible to improve the sensor performance (specifically, to broaden the frequency range, reduce the amplitude-frequency characteristic (AFC) unevenness, and reduce the nonlinear distortion factor (NDF) value). The operating principle of these devices is outlined. The basic characteristics such as AFC, NDF, and the inherent noise level are determined experimentally, and the methods of their determination are described. The obtained data are analyzed and compared to the data on similar foreign devices. Principal lines of further research aimed not only at improving the technical characteristics but also at establishing a serial production process are specified.

Precession Azimuth Sensing with Low-Noise Molecular Electronics Angular Sensors

This paper describes the use of MET-based low-noise angular motion sensors to precisely determine azimuth direction in a dynamic-scheme method of measuring the Earth’s rotational velocity vector. The scheme includes sensor installation on a rotating platform so that it could scan the space and seek for the position of the highest Earth’s rotation vector projection on its axis. This method is very efficient provided a low-noise sensor is used. A low-cost angular sensor based on MET (molecular electronic transduction) technology has been used. The sensors of this kind were originally developed for seismic activity monitoring and are well known for very good noise performance and high sensitivity. This approach, combined with the use of special signal processing algorithms, allowed reaching the accuracy of 0.2°, while the measurement time was less than 100 seconds.

Design and Self-Noise of MET Closed-Loop Seismic Accelerometers

Molecular electronic transfer (MET) technology offers an alternative approach for the development of accelerometers with high dynamic range and low self-noise. The best performance is achieved by using a force-balancing feedback. However, the operating principles of the feedback sensors has not been reporting yet, also, there is not any comprehensive theoretical model describing sensor noise in the complete operating frequency range. This paper reports on the development of the feedback system for an MET seismic accelerometer, a feedback stability analysis, and an optimization of the signal conditioning feedback electronics to get the highest dynamic range. Also, both the theoretical model and experimental results of such sensors self-noise are presented in the range of 0.1–120 Hz. According to the model and the experimental observation, there are two major contributors into self-noise: convective processes in the electrolyte and electronic noise of the signal operational amplifiers. The research results give better understanding of the molecular electronic accelerometers noise nature and suggest ways to reduce it.

Molecular electronic transducer based planetary seismometer with new fabrication process

This paper describes a novel design and implementation of a short period seismometer based on molecular electronic transducer (MET) for the purpose of planetary exploration. A silicon on insulator (SOI)-based micro-fabrication is employed to reduce the hydraulic impedance of microfluidic channels in a MET device, resulting in improved noise floor and sensitivity. The resolution reached 1.78×10-7 (m/s2)/√Hz at 1.2 Hz with the sensitivity of 2500V/(m/s2).

Angular Molecular–Electronic Sensor with Negative Magnetohydrodynamic Feedback

A high-precision angular accelerometer based on molecular–electronic transfer (MET) technology with a high dynamic range and a low level of self-noise has been developed. Its difference from the analogues is in the use of liquid (electrolyte) as the inertial mass and the use of negative feedback based on the magnetohydrodynamic effect. This article reports on the development of the angular molecular–electronic accelerometer with a magnetohydrodynamic cell for the creation of negative feedback, and the optimization of electronics for the creation of a feedback signal. The main characteristics of the angular accelerometer, such as amplitude–frequency characteristics, self-noise and Allan variance were experimentally measured. The obtained output parameters were compared to its analogues and it showed perspectives for further development in this field.