GE CTR 80 - Manual (Page 43)

down. In this way the temperature is maintained at a fairly constant
temperature.
The temperature stability of the bath and response time depend on the width of
the proportional band. If the band is too wide the temperature will deviate ex-
cessively 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 propor-
tional 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. This value is usually two
to three times the largest value at which the bath temperature oscillates.
The proportional band width is set at the factory to a value between 0.5 and
1.0°C. The proportional band width may be altered by the user if he desires to
optimize the control 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
12.0 P
Heater power in percent
S
Access proportional band
ProP Flashes “ProP” and the setting
15.0 Proportional band setting
To change the proportional band press “UP” or “DOWN”.
1.5
New proportional band setting
To store the new setting press “SET”. Press “EXIT” to continue without storing
the new value.
S
Accept the new proportional band setting
40
9 Controller Operation