122-28176 Parallax Inc, 122-28176 Datasheet - Page 222

• Manufacturer Part Number: 122-28176
• Description: GUIDE STUDENT PROCESS CONTROL
• Manufacturer: Parallax Inc

Specifications of 122-28176

• Accessory Type: Manual
• Product: Microcontroller Accessories
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• For Use With/related Products: Propeller Education (PE) Kit
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Contains lead / RoHS non-compliant

For a moment, consider the factors that would affect the output temperature. Obviously,
ambient temperature is one. Can you list at least three others? How about:
These are all factors that represent BTUs of heat energy taken away from the process.
Therefore, they also represent BTUs that must be delivered to the process if the desired
output is to be achieved. If the drive on the heating element was adjusted to deliver the
exact BTUs being lost, the output would be stable.
In theory, the drive level could be set and the desired output would be maintained
continuously, as long as the disturbances remained constant. Let’s now assume that it is
your objective to keep the interior of your system at a constant temperature. A good real-
world example is that of an incubator used to hatch eggs. To hatch chicken eggs, it is
important to maintain a 101.5 °F environment.
Turning on the heater will warm up the interior of the test tube. In our earlier test, you
turned on the heater’s drive transistor, and the temperature rose above 101 °F. Obviously,
to maintain the desired temperature, you will not need to have full power applied to the
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The rate at which material is flowing through the tank.
The temperature of the material coming into the tank.
The magnitude of air currents around the tank.
Figure 6-22
Liquid Heating
System