Fluke 9140 User Manual page 33

9140 Dry-well Calibrator
User's Guide
28
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 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 temperature may swing back and forth be-
cause the controller overreacts to temperature variations. For best control stabil-
ity the proportional band must be set for the optimum width.
The proportional band width is set at the factory to 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 front panel. The width
may be set to discrete values in degrees C 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 the heater
power. Then press "SET" to access the proportional band.
S E
+
Access heater power in secondary menu
Flashes SEC for secondary menu and then displays the
SEC
heater power
Heater power in percent
12.0P
S
Access proportional band
PROP Flashes Prop then displays the setting
Proportional band setting
4.1
To change the proportional band press "UP" or "DOWN".
New proportional band setting
10.0
To accept the new setting press "SET". Press "EXIT" to continue without stor-
ing the new value.
S
Accept the new proportional band setting