The AD has one capacitance input channel, while the AD has two channels. Each channel can be configured as single-ended or differential. For capacitive sensors with one plate connected to ground, the AD is recommended. The parts have an on-chip temperature sensor with a resolution of 0. The on-chip voltage reference and the on-chip clock generator eliminate the need for any external components in capacitive sensor applications.
The parts have a standard voltage input, which together with the differential reference input allows easy interface to an external temperature sensor, such as an RTD, thermistor, or diode.
Both parts can operate with a single power supply from 5. Automotive, industrial, and medical systems for Pressure measurement Position sensing Level sensing Flowmeters Humidity sensing Impurity detection. Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use.
Specifications subject to change without notice. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. One Technology Way, P. Box , Norwood, MA , U. Tel: A monolithic precision capacitive sensor interface based on a Sigma-Delta core is presented.
All necessary functions such as sensor excitation, temperature sensor, voltage reference, etc. View 1 excerpt, references methods. A sensitive differential capacitance to voltage converter for sensor applications. Materials Science, Computer Science. IEEE Trans. An interface circuit for high-accuracy signal processing of differential-capacitance transducers. An interface for a capacitive pressure sensor which accommodates digital encoding and linearization functions has been developed.
The front-end is a switched-capacitor bridge which converts the … Expand. A miniature pressure system with a capacitive sensor and a passive telemetry link for use in implantable applications.
Journal of Microelectromechanical Systems. A miniature telemetric pressure-measuring system is presented in this paper. The system uses passive telemetry to transfer power to the transponder and pressure data to the remote base unit. Such … Expand. View 1 excerpt, references background. A wireless batch sealed absolute capacitive pressure sensor.
The bit AD , with its two capacitance measurement channels, could be useful for this kind of application. The range of end uses could include a medical probe that needs to rest flush on the skin, a biopotential electrode sensor, or the housing holding a catheter tube in place. Once the electrode information is available, a simple algorithm running on the host controller could be applied to determine if all sensor electrodes were making proper contact with the skin.
The examples shown in Figure 6 use capacitive sensors in an unconventional way: a user positions a device containing the capacitive sensing electrodes on the human body, in contrast with the traditional capacitive sensing human interface applications, where a person typically initiates contact with the sensor electrodes by finger touch.
In some medical and fitness-testing equipment, there is a need to measure perspiration from a human body. However, if the measurement needs to be performed without galvanic contact, this function can be implemented by detecting the humidity near the human body using a capacitance sensor. When people sweat, the humidity dielectric constant close to the human skin increases; a noncontacting electrode in this vicinity could be used to measure the resulting change in capacitance.
It may be useful to add a second capacitance sensor to measure the ambient humidity and use it for common-mode compensation. In one approach, shown in Figure 7, an excitation plate is put on the back of the patient while the sensor electrode belt is fastened on the right side of the chest of the patient. As the lungs fill and empty, the resulting chest movements change the distance between two plates.
The dielectric constant will also change because of the complex physiological activities during breathing. These capacitance changes can be measured by CDC devices. This may be an interesting topic for further research.
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