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High-sensitivity capacitive sensing: tune for speed, resolution or power

High-sensitivity capacitive sensing: tune for speed, resolution or power

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By eeNews Europe



When optimized for speed, the PCap04 can capture and digitize up to 50,000 sensor measurements per second. When sampling at a slower rate to optimize for precision, the PCap04 can achieve a measurement resolution of 8 aF [atto-Farads, 1 aF = 10-18F: 1 pF = 106 aF].

 

The configurability of the device also enables sensor manufacturers to trade measurement speed off against power consumption. In low-power mode, the PCap04 draws a current as low as 4.0 µA. ams has developed a demonstration board with no external power supply, in which the PCap04 operates on the energy harvested from the RF field generated by an NFC reader such as a smartphone.

 

The PCap04 IC is intended for use with any sensing element that generates a change in capacitance. Featuring six capacitance measurement channels, it is suited to use with sensing elements which measure parameters such as pressure, force, position, tilt, humidity, weight, level and many others.

 

The PCap04’s output may be supplied as a PWM or PDM representation of the raw measured capacitance value. The device also features a DSP to process the sensor measurements and convert them into digital values transmitted via an I2C or SPI interface. It can handle input capacitance values over a range from 1 pF to 100 nF.

 

The PCap04 provides various built-in configuration options, including support for grounded, floating, differential and differential grounded sensor connections. The DSP can run ams open-source code as well as user-generated code for functions such as measurement linearization and conversion. ams provides an evaluation kit and a user-friendly software development tool which make it easy for the design engineer to develop, test and debug code to run on the PCap04.

“The PCap04 gives sensor manufacturers a flexible alternative to other sensor front ends on the market today that have have fixed operating characteristics. It offers the unique advantage of enabling sensor manufacturers to fine-tune the operation of the sensor front end to meet the requirements of their specific application,” said Jose Vinau, Marketing Director for Medical and Specialty Sensors at ams.

 

The PCap04 is supplied as a bare die, or housed in a QFN-24 plastic package for $2.95 (1,000). An evaluation board, the EVAL-PCAP04, is available at the ams ICdirect online store.

 

ams; www.ams.com/PICOCAP-Capacitive-Sensing/Pcap04

 

 

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