EE445L : Lab 7 Temperature Data Acquisition System

I am taking a class called EE445L which is microcontroller applications. It is a mainly lab based class where we design and prototype a new embedded system every week. We are using the Texas Instruments LM3S1968 Evaluation Board. The microcontroller is a ARM Cortex M3. It has an on board OLED display and a USB debugger. It is a fairly impressive piece of kit.

This is Lab 7 which is a Digital Thermometer. I can not post the code or schematics due to this being a Lab and it would be looked upon as academic dishonesty.

Lab 7 Problem Statement.

The Thermistor is a non linear device. That is as temperature increases linearly the resistance across does not scale linearly. Part of the circuit involves a resistor “bridge” this is a non linear setup. If you combine two non linear systems you can roughly get a linear system. It is not perfect but it is close enough.

After the bridge part the voltage level goes into an amplifier which boosts the signal to a level that the LM3S1968 can read via its ADC (Analog to Digital Convertor) ports. This signal is the passed through a Low Pass filter. The filter is set to cut off at 10Hz. The LM3S1968 is configured to sample at 100Hz. The signal is low passed to prevent aliasing from high frequencies which would cause interesting glitches on the ADC.

I will be recording all the major EE445L labs in the next coming days.

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