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
excessivelyfrom the set-point due to varying external conditions. This is be-
cause 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 temperaturemay swing back and forth be-
cause the controller overreacts to temperature variations. Forbest control stabil-
ity the proportional band must be set for the optimum width.
The proportional band width is set at the factoryto about 15.0°C. The propor-
tional band width may be altered by the user if he desires to optimize the con-
trol characteristics for a particular application.
The proportional band width is easily adjusted from the frontpanel. The width
may be set to discrete values in degreesC or F depending on the selected units.
The proportional band adjustment is be accessed within the secondary menu.
Press “SET” and “EXIT” to enter the secondary menu and show theheater
power.Then press “SET” to access the proportional band.
S+EAccess heater power in secondary menu
SEC Flashes SEC for secondary menu and then displays the
heater power
12.0P Heater power in percent
SAccess proportional band
PROP Flashes Prop then displays the setting
4.1 Proportional band setting
Tochange the proportional band press “UP” or “DOWN”.
10.0 New proportional band setting
Toaccept the new setting press “SET”. Press “EXIT” to continue without stor-
ing the new value.
SAccept the new proportional band setting
9140 Dry-well Calibrator
User’s Guide
28