29.3 DESIGN CASES
29.3.1 Oven Temperature Control
Design an analog controller that will read an oven temperature, and when it passes 1200 degrees the oven will be turned off. The voltage from the thermocouple is passed through a signal conditioner that gives 1V at 500F and 3V at 1500F. The controller should have a start button and E-stop.
29.3.2 Statistical Process Control (SPC)
We can do SPC checking using analog inputs, and built in statistics functions.
Recall the basic equations for a control chart.
The general flow would be,
2. Randomly select values and calculate the average and store in memory. Calculate the standard deviation of the stored values.
3. Compare the inputs to the standard deviation. If it is larger than 3 deviations from the mean, halt the process.
4. If it is larger than 2 then increase a counter A, or if it is larger than 1 increase a second counter B. If it is less than 1 reset the counters.
5. If counter A is =3 or B is =5 then shut down.
