Analog front-end IC linearizes sensors

Analog front-end IC linearizes sensors


Susan Nordyk @ 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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Bob Kondner


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.)

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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