Analog front-end IC linearizes sensors

Analog front-end IC linearizes sensors

Susan Nordyk @ edn.com discuss about LTC2986 which is able to digitize and linearize a combination of temperature sensors in Celsius or Fahrenheit degrees.

A 10-channel temperature-measurement IC, the LTC2986 from Linear Technology directly digitizes any combination of thermocouples, RTDs, thermistors, and external diodes with 0.1°C accuracy and 0.001°C resolution. The analog front-end device combines three 24-bit delta-sigma ADCs with all the necessary excitation and control circuits for each sensor. On-chip EEPROM stores user configuration data and custom sensor coefficients, eliminating IC or sensor programming by a host processor.

The LTC2986 measures absolute microvolt-level signals from thermocouples and ratiometric resistance from RTDs and thermistors. It performs linearization and outputs the results in °C or °F. With 10 analog inputs, the LTC2986 accommodates up to 9 thermocouples, 4 RTDs, 4 thermistors, and/or 10 diodes, with support for Type B, E, J, K, N, S, R, and T thermocouples; 2-wire, 3-wire, and 4-wire RTDs; and 2.25-kΩ to 30-kΩ thermistors.

Analog front-end IC linearizes sensors – [Link]

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Mike is the founder and editor of Electronics-Lab.com, an electronics engineering community/news and project sharing platform. He studied Electronics and Physics and enjoys everything that has moving electrons and fun. His interests lying on solar cells, microcontrollers and switchmode power supplies. Feel free to reach him for feedback, random tips or just to say hello :-)

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Bob Kondner

Hi,

Just a quick note I found in this area that I used in a SunDuino product.

Digikey sells a tiny precision thermistor that is .5% trimmed and costs about $3.00 in small quantities. I believe it is used in digital thermometers and does not require any trimmers. (Not positive about that,)

The temp / resistance of a thermistor is very non-linear but adding a parallel resistance will help make it more linear. I use it with an 10 bit ADC in a PIC and I resolve it to 5 degree C measurements from -40 to +85. I used a piece wise linearization table in code. Works very well. I use this for monitoring battery temperatures during use and charging. The key to use is padding with a resistor but make sure you have sufficient sensitivity at the endpoints. (I worked with only 8 bits of the DAC, using the full 10 bits would help. (Though that 10th bit is not super useful.)

http://www.digikey.com/product-search/en?keywords=317-1305-ND

I have schematic on my site if you have interest.

Bob K.

PS: don’t trust any battery charger that does not monitor temp. Simple a must have.

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