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Controller Operation
9.7 Proportional Band 9
9-7
The heater power display is accessed in the secondary menu. Press “SET” and
“EXIT” simultaneously and release. The heater power will be displayed as a
percentage of full power.
100.00C Well temperature
+ Access heater power in secondary menu
SEC Flashes
12.0 P Heater power in percent
To exit out of the secondary menu hold “EXIT”. To continue on to the proportional
band setting function press “EXIT” momentarily or “SET”.
9.7 Proportional Band
In a proportional controller such as this the heater output power is proportional to
the well temperature over a limited range of temperatures around the set-point.
This range of temperature is called the proportional band. At the bottom of the
proportional band the heater output is 100 %. At the top of the proportional band
the heater output is 0. Thus as the temperature rises the heater power is
reduced, which consequently tends to lower the temperature back down. In this
way the temperature is maintained at a fairly constant temperature.
The temperature stability of the well and response time depend on the width of
the proportional band. If the band is too wide the well temperature will deviate
excessively from the set-point due to varying external conditions. This is because
the power output changes very little with temperature and the controller cannot
respond very well to changing conditions or noise in the system. If the
proportional band is too narrow the temperature may swing back and forth
because the controller overreacts to temperature variations. For best control
stability the proportional band must be set for the optimum width.
The proportional band width is set at the factory to about 5.0 °C. The proportional
band width may be altered by the user if he desires to optimize the control
characteristics for a particular application.
1.888.610.7664 sales@GlobalTestSupply.com
Fluke-Direct.com
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