Proportional Band - Fluke 9133 User Manual

9133
User's Guide
7.9
24
12.0P Heater power in percent
To exit out of the secondary menu press and hold the "EXIT" button. To con-
tinue on to the proportional band setting function, press the "SET" button.

Proportional Band

In a proportional controller such as this, the heater output power is propor-
tional to the target temperature over a limited range of temperatures around
the set-point. This range of temperature is called 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. In this way the temperature is maintained at a
fairly constant level.
The temperature stability of the instrument depends on the width of the
proportional band. If the band is too wide, the target temperature deviates
excessively from the set-point due to varying external conditions. This devi-
ation is caused by the power output changing very little with temperature
and the controller not responding 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 vari-
ations. For best stability control, the proportional band must be set for the
optimum width by the user in any given application.
The optimum proportional band width is set at the factory to about 25.0°C.
The user may alter the proportional band width to optimize the control
characteristics for a particular application. However, we recommend the
proportional band be changed only by knowledgeable personnel.
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 se-
lected units. The proportional band adjustment can be accessed within the
secondary menu. Press the "SET" and "EXIT" buttons to enter the secondary
menu and show the heater power. Then press the "SET" button to access
the proportional band.
S+E
Access heater power in secondary menu
SEC Flashes
heater power
12.0P Heater power in percent
S
Access proportional band
Prob Flashes
the proportional band setting
for secondary menu and then displays the
for proportional band and then displays