The first attempts to develop solion-based transducers using a liquid inertial mass date back to World War II and were directly related to the control systems developed for German V-I and V-II rockets. Not all of these attempts were successful, and for the next twenty years research and development in these devices was minimal.
Electrochemical transducer research resumed in the U.S. between 1950 and 1960 under the direction of the U.S. Navy. The main objective was to develop highly sensitive, low power seismometers.
Research progressed into the mid-1970s without significant progress. The seismometers that were developed were several times larger than comparable electromechanical devices, and had higher self-noise. These attempts were unable to achieve a flat transfer function over a wide frequency range or to solve the problem of long-term stability. The interest in utilizing liquid inertial mass devices was rekindled in recent years. Fundamental research in the molecular-electronic principle of conversion were conducted by Dr. V. A. Kozlov and Dr. V. Agafonof.
The resulting transducer was named “molecular-electronic transducer”, or MET. MET Tech produces a line of sensors based on Molecular Electronic Technology (MET). These sensors include linear accelerometers, angular accelerometers, rate sensors and gyroscopes. The core process underlying Molecular Electronic Technology is the convection of liquid under external movement. The liquid plays the role of the inertial mass, while hydrodynamic impedance of the sensing element acts as the damping mechanism providing a feedback for stabilization of the transfer function.
The sensing element of a MET sensor comprises a sealed housing with a channel that is filled with electrolyte as the liquid agent and electrodes that are positioned across the channel. The electrodes are separated by dielectric spacers. The electrodes and spacers are perforated to control the hydrodynamic impedance that in turn determines the accelerometer pass band, dynamic range, and sensitivity.
Key Characteristics
The unique principles behind MET sensors contribute to three key qualities:
1) Low Noise: The noise floor of MET sensors is extremely low and flat starting from values near DC. This derives from the high internal gain of MET sensors, whereby the sensing element’s intrinsic noise dominates over that of the signal conditioning electronics including the low frequency flicker noise.
2) Small Size: MET sensors can be made very small without sacrificing sensitivity. They require only a few grams of liquid agent in order to achieve a high degree of sensitivity, because the molecular electronic transformation of the input signal in these sensors is extremely efficient.
3) Low Power: MET sensors consume very little power due to the small size of the electrodes, low ion concentration in the liquid agent and small electrical voltage applied between the electrodes.
In short, the combination of high sensitivity, large dynamic range, and a wide pass band distinguishes MET sensors from conventional MEMS.
