03/05/15 (Week 2)

Quiz 1

In class today we learned how to use nodal analysis to solve a circuit by creating a system of equations and solving for the missing variables. 

Temperature Measurement System

In this experiment we are testing how temperature changes the resistance within a resistor. In the circuit diagram we get a resistor that is a control, which will not change temperature. We then find which resistors to use to get a voltage change of at least 0.5 volts. Once we find these calculations we can test this experimentally.

Here we set up Analog Discovery to the above circuit with the two resistors we calculated.

It turned out that our measured value for resistors didn't give us the voltage change we desired. We only got a voltage change of 0.43 volts. This is real world engineering, we needed to use a 4.3 kOhm resistor but they don't exist. So we stepped up the resistance to 4.7kOhms. Since we fell short we decided to step down the voltage to 3.9kOhm. This made our change in voltage even lower. So for attempt number 3 we stepped up the voltage to 5.6kOhm. Here we got a voltage change of 0.51 volts which is what we were looking for.

Our calculated values didn't quite work out in the real world perspective. We needed to step up the resistor from 4.3kOhm to 5.6kOhm. That is quite a jump in resistance. One of the contributing factors to this is that we assumed that the room was 22 degrees Celsius and our finger tips were at average body temperature. But in reality the room was probably colder and our finger tips were also colder than average body temperature. So we calculated what change in voltage the new resistors would have given us. It turns out it was still only 5.5% off.