Day 4 3/3 Nodal Analysis.

Today, at the beginning of the class, we  did a quiz about finding the voltage in the circle. we first use KCl ways to solve and then professor gave us a nother way to solve it.

 And we find it is hard to do.

Experiment: Temperature Measurement System

Purpose: In this lab, we need to design a circle which has an output voltage depending on temperature and analyze is as a function of Rth and R. There is a key equipment called thermistor, whose resistance will decrease according to the increase of temperature so that the output voltage can increase.

In this photo, we first find the voltage resolution is 5/256=0.0198 and between the temperature 25C to 37C the change of temperature is 12 and the change of voltage is 5 then we find the temperature resolution is 0.48C.

 Pre- lab question:

In this photo, we did the pre-lab question. From the graph of lab manual, we find that at room temperature, the resistance of thermistor is 11000 ohm. At body temperature, the resistant is 7000 ohm. we know that the change of voltage is 0.5V, then we find the range of resistor is from 4376 to 17633 ohms.

In this photo, we take a 5.6Kohm resistor, but we measure the actual resistance of it is 4.67 ohms.

In this photo, we use the 5V power supply.

In this photo, we set up the circle and  At room temperature, We measured the voltage across the resistor is 1.51 V.Then, we used our hand as body temperature to heat up the Rth. The voltage we measured is 2.04V.

In this photo, we record the data we measure. and find the change of voltage is 0.53 and calculated the error is 6%. 

 Post-lab Question:

We are then asked to design a new circuit that the output sensitivity of the device must be at least 0.1 V/degree. After our calculation, we find that it is impossible to get it. The maximum we can get a difference of 0.563 V in 12 degree’s difference. Our lab data is bigger than the maximum probably the difference in our temperature is higher than 12 degrees. 

Here we chose the ground to be the lower node. Applied node voltage to essential nodes, we were able to find the V1, V2 respectively

Summary:

Today, we talk more about nodal analysis. We find that using nodal analysis make us have less algebra to do.We do the experiment about Temperature Measurement System by using a thermistor that can change its resistance when temperature changes.