122-28176 Parallax Inc, 122-28176 Datasheet - Page 242

• 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

limit, full appropriate action is taken to drive the temperature to the opposite limit. Full
opposite action is then taken to drive the process back again. Figure 7-7 graphically
diagrams the action taken by differential-gap control. When the system is started and its
temperature is below the lower limit, the heater will come on and the temperature rise.
When the temperature passes the upper limit, the heater is turned OFF, heat will begin to
leave the process, and the temperature will begin to drop to below the lower limit. The
heat then is turned back on and the cycle begins again.
Notice how the diagram in Figure 7-8 differs from the earlier one depicting noisy data in
a simple on-off control mode.
Because the differential gap is wider than the effect of the noise, rapid cycling is
eliminated. These advantages come at the compromise of allowing the measured variable
to drift further from the desired “average” value. The thermal inertia of our system will
Figure 7-7
Differential Gap
(Hysteresis) Control
Graph
Figure 7-8
Effects of Noise on
Control Using
Differential-Gap