04/07/2016

04/08/2016: Cascaded Op ams and Temperature Measurement System Design

I. Introduction:

Today we spent most of our time studying op ams, which indicated the connection between many op ams in one circuit. The system in return would be more complex but not impossible to analyze using nodal analysis. For today lesson, we would have to use many combinations of summing amplifier op ams, inverting and so on

Here is a picture of inverting cascard op ams.

Professor Mason asked us to determine the type of op ams circuit  he put on the screen. We chose inverting for a and b due to their terminal, c is summing because has more than one op am

Here is a picture of cascaded op ams. We found the V1 using the formula we nodal analysis, and using the same approach to find V_2, notice that they were all determined by Vs and those resistors

We plugged the numbers into the formulas we had derive previously solving for V_2 and i_0

II. Temperature Measurement System Design
1. Introduction:
For this lab, we used the wheatstone bridge circuit to convert resistance to a voltage change. The change in resistance was determined by the thermistor. The change in voltage was the change Voutput on the side of the op am

For this picture, my lab partner Carlos derived the expression for Vab, 

Here is the drawing for our circuit, it took us 15 mins to decide our values for the resistors, we also went around to check with other groups

The last equation is the most important equation for this lab, for this part, we used Maple to solve for Vo symbolically

Here is my setup for the wheatstone. 

Here is the direct view of my wheatstone design

d

Last but not least, here Professor Mason introduced use to use bit representation for the resistors, except that the power would be negative instead of positive, made them a fraction

IV. Summary:

After many experiments, we believe nodal analysis worked best compared to other techniques that we have learned so far. For today lab, we spent most of our time understanding the cascaded circuit. We derived many formulas for summing amplifiers, difference op ams, and so on. For the lab, we only did the wheatstone lab, but it took us a lot of time to figure out the right design, the good thing about the wheatstone is that we could use it to convert the change in resistance to the change in voltage