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Signal conditioner ups capacitive sensor accuracy

Posted: 02 Mar 2011 ?? ?Print Version ?Bookmark and Share

Keywords:capacitive? sensor? signal? conditioners?

ZMD AG expands its family of capacitive sensor signal conditioners (SSCs) with the introduction of the ZSSC3122 cLite device. The chip delivers 14-bit resolution and 0.25 percent full-scale-output accuracy. It features a built-in sleep mode lowers current consumption to battery applications, as well as industrial and rugged environments. It also works with MEMS sensing elements such as pressure sensors for hydraulic control systems, humidity sensors and liquid level gauges also benefit from these features.

Capacitive sensors are a preferred option for industrial linear and angular position sensors and contactless potentiometers where harsh or explosive environments make other sensor technologies impractical because they do not touch or make direct contact with the system being sensed.

Their small size and lower power consumption also make them preferable over resistive bridge sensors. The ZSSC3122 supports this with as low as 60?A operating current over the entire voltage range of 1.8V to 5.5V.

The SSC can be configured to interface with capacitive sensors from 2pF to 10pF with sensitivity as low as 125aF per digital bit. The part accommodates single and differential input sensor configurations. All calibration is digital and completed in one pass, eliminating the cost of laser trimming and speeding production of fully calibrated sensor modules.

It connects to MCUs but can also be used in standalone designs for transducer and switch applications. The mixed-signal design of cLite offers 14-bit capacitive-to-digital conversion and full 14-bit compensation of sensor offset, sensitivity and temperature via an internal digital signal processor running a correction algorithm. Calibration coefficients are stored in an on-board non-volatile EEPROM. The system interface offers I2C, SPI, PDM or alarm outputs.

The standard supply voltage is 1.8 to 5.5 V with accuracy up to 0.25 percent over a -40C to +125C range. Programming and single-pass calibration of the capacitive sensor and the ZSSC3122 is available through a standard PC environment using the ZSSC3122KIT development tools. The package includes TSSOP 14, a development board, USB cable and calibration software.

ZSSC3122 samples are available. Unit prices start at $4.54, in volumes of 1k devices.

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