Day 4

Today we did a lab on thermistors and learned how to use nodal analysis to solve circuits.

Here was our first class fiesta where we attempted to use KCL and KVL to find currents and resistances.

The objective of this lab is to design a temperature measurement system using a thermistor. Using the resistance curve for our thermistor, see that at room temperature the resistance is 11k ohms and at body temperature it's 7k ohms. We are to pick a resistance value that will give is a minimum delta voltage of 0.5V. 

In order to get a change of .5V, we calculated that we would need the resistance values that are boxed. Since those exact resistance values are not available to us, we are to pick resistance values that are close.

Here  we are measuring the thermistor's resistance as it reaches body temperature. We measured a resistance at 37°C to be 11.54k ohms and 25°C to be 8.0k ohms. This results in a 5% and 14% error respectively.

As shown above, we used resistance values that were close to our calculated resistances in order to get the 0.5 delta voltage. We found the 12k ohm resistor to give us the change in voltage that we were looking for. We believe the calculated resistances to have a large uncertainty since we are not sure of the actual temperatures that the thermistor sees, as well as the efficiency of the thermistor (which can be apparent when we measured the resistance of the resistor at body and room temperatures respectively. 

Here we learned and practiced nodal analysis using V1 and V2 as our nodes and the bottom branch as the reference.