Analog Devices Conductivity Sensor

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David Bengtson

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Nov 10, 2016, 9:16:02 PM11/10/16
to plots-waterquality


Analog Devices has just published a nice design for an pretty accurate conductivity sensor

http://www.analog.com/en/design-center/reference-designs/hardware-reference-design/circuits-from-the-lab/CN0359.html#rd-overview

from the blurb

"

A carefully selected combination of precision signal conditioning components yields an accuracy of better than 0.3% over a conductivity range of 0.1 μS to 10 S (10 MΩ to 0.1 Ω) with no calibration requirements.


Automatic detection is provided for either 100 Ω or 1000 Ω platinum (Pt) resistance temperature devices (RTDs), allowing the conductivity measurement to be referenced to room temperature.


The system accommodates 2- or 4-wire conductivity cells, and 2-, 3-, or 4-wire RTDs for added accuracy and flexibility.

"


While it's a pretty complicated schematic, the design documentation has some good explanations of the requirements for good accuracy.


Dave

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