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Capacitive sensors are constructed from many different media, such as copper, indium tin oxide (ITO) and printed ink. Copper capacitive sensors can be implemented on standard FR4 PCBs as well as on flexible material. ITO allows the capacitive sensor to be up to 90% transparent (for one layer solutions, such as touch phone screens).
Each capacitor sensor consists of two metal rings mounted on the circuit board at some distance from the top of the access tube. These rings are a pair of electrodes, which form the plates of the capacitor with the soil acting as the dielectric in between. The plates are connected to an oscillator, consisting of an inductor and a capacitor. The ...
Capacitive displacement sensors can be used to measure the position of objects down to the nanometer level. This type of precise positioning is used in the semiconductor industry where silicon wafers need to be positioned for exposure. Capacitive sensors are also used to pre-focus the electron microscopes used in testing and examining the wafers.
These long wavelengths allow the technology to operate under the quasi-electrostatic regime. As long as the diameter of the sensor is much smaller than the length of the wave, these assumptions hold valid. For instance, when exciting with 2 MHz AC signal, the wavelength is 149.9 meters. Sensor diameters are typically designed well below this limit.
An electronic speed control follows a speed reference signal (derived from a throttle lever, joystick, or other manual input) and varies the switching rate of a network of field effect transistors (FETs). [1] By adjusting the duty cycle or switching frequency of the transistors, the speed of the motor is changed. The rapid switching of the ...
Figure 3. In the flat region, the sensor can be modeled as a voltage source in series with the sensor's capacitance or a charge source in parallel with the capacitance. Piezo sensors typically use the flat region of the frequency response (the "usable region" in Figure 1) between the high-pass cutoff and the resonant peak.
The closely related split stator variable capacitor does not have the limitation of 90° angle since it uses two separate packs of rotor electrodes arranged axially behind one another. Unlike in a capacitor with several sections, the rotor plates in a split stator capacitor are mounted on opposite sides of the rotor axis.
The start capacitor is typically mounted to the side of the motor housing. These are called capacitor-start motors, and have relatively high starting torque. There are also capacitor-run induction motors which have a permanently connected phase-shifting capacitor in series with a second winding. The motor is much like a two-phase induction motor.