Practical signal conditioning

Objectives: Build a circuit that is able to show conversion of temperature from degrees Fahrenheit to degrees Celsius, and also get more familiar with the use of op amps.

Procedure:

Step 1. Testing: We will connect everything to check that our semiconductor LM35(Temperature sensor) is working properly assuming 1C equals 10mV.

We observe that it is working properly and now we can move ahead to the actual experiment.

The function that lets us convert from degrees f to degrees c and vice-versa is the following and we will use it to proceed with our calculations.

    Tf=1.8 Tc+32

This is the function transformed in therms of resistance and voltages where vf is the temperature in fahrenheit and vc is the temperature in Celsius. We calculate our resistances from a ratio of 4/5 so that means than R2 has to be 0.8 times smaller than R1.

Step 2: Determine R1 and R2

We decided to use 8.2k ohms for R2 and 10K ohms for R1 since we were not able to find exactly the ratio mentioned before. 

Now we have to set up the following circuit and also we found Vref to be -0.4V 

Step 3: Set up the circuit

And this is how we did it. We later had to do a voltage divider because Vref is too small for us to provide to the system and we ended up getting Vc =24mV and Vc=76.2mV

Step 4: Calculations

After that we find the percent to see how far is our circuit from being very accurate and efficient

Observations: Our circuit shows a 1.33% error which is pretty good. We consider it to have successfully achieved the main objective. We surely became more familiar with op amps and also with the semiconductor LM35 and surely understand how useful are these two for applications in real life.