Discussion on Capacitance and Digital Converter Technology in Healthcare Applications
In recent years, advances in electronic technology have created conditions for many innovations and improvements in the healthcare industry. Challenges for healthcare devices include new diagnostics and treatments, remote monitoring, development of home care equipment, improved quality and reliability, and increased flexibility and ease of use.
For more than 40 years, Analog Devices' extensive and comprehensive linear, mixed-signal, MEMS, and digital signal processing technologies have revolutionized the design of medical devices for instrumentation, imaging, and patient monitoring. This article will focus on capacitive digitizer (CDC) technology, which makes it possible to use high-performance capacitive sensing in healthcare applications.
Capacitive touch sensor controller - a new user input method
The capacitive touch sensor provides a user interface in a manner similar to the buttons, sliders, scroll wheels or other means shown in FIG.
Figure 1. Touch sensor layout example
Each blue geometric region represents a sensor electrode on a printed circuit board (PCB) that forms a plate of the virtual capacitor. The other plate is made up of the user's fingers, which are actually grounded relative to the sensor input.
The AD7147/AD7148 CapTouch controller family is designed to excite and interface with capacitive touch sensors to measure capacitance changes from single-electrode sensors. The device first outputs an excitation signal to charge the capacitor plates. When an object (such as a user's finger) is close to the sensor, the user acts as a capacitor for the capacitor, which will form a virtual capacitor (Figure 2). This capacitance can be measured using a capacitance-to-digital converter (CDC).
Figure 2. Schematic diagram of capacitance detection and typical response
The CDC is able to sense the change in capacitance of the external sensor and use this information to record sensor activation events. The AD7147 and AD7148 have 13 and 8 capacitor inputs, respectively, and are equipped with on-chip calibration logic to compensate for measurement changes caused by environmental changes to ensure that they are not generated on external sensors due to temperature changes or humidity changes. False trigger event.
The AD7147 and AD7148 offer multiple operating modes, user-programmable conversion sequences and extremely flexible control functions. These features make it ideal for high-resolution touch sensor functions such as sliders or scroll wheels, and they have low software requirements. In addition, button sensor applications can be fully implemented with on-chip digital logic without the need for any software.
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