Marathon Computer UNIPRO V3.5 - Manual (Page 8)

Marathon Monitors Inc
.
Unipro 3.5 Process Control 1 Aug. 1997
Three types of Proportional control are:
1. Time-Proportioning: Referring to the
modulation of the duty cycle. That is,
changing the ratio of On Time versus Off
Time in systems that use such devices as
heating elements, electronically
operated/assisted valves, or servo drives that
use analog command signals for control.
2. Position-Proportioning: Referring to the
adjustment of a variable positioning device
such as a positioning motor with slidewire
feedback.
3. Voltage or Current Output Proportioning:
An Analog output's (voltage or current)
amplitude is varied based on input from
rheostats, thermocouples, ammeters, etc. to
control heat applications.
The UNIPRO provides many ways to use the above control
methods. Setup has details for setting the Control Modes to
determine the method to be used. Some typical applications for the
Proportioning method are:
1. HIGH/LOW or HEAT COOL heat application system: Set
Control Modes for Time-Proportioning. This provides that
CONTROL OUTPUT #1 (TBA-7, TBB-7) and CONTROL
OUTPUT #2 (TBA-8, TBB-8) are in opposite conditions at either
extreme of the control range and are both OFF at the midpoint of
the control range.
2. ANALOG OUTPUT control: Set Control Modes for
Time-Proportioning. This provides a 0 to 5 VDC or 4 to 20 mA
output which is selectable on the ANALOG OUTPUT BOARD
(TBD-13 through TBD-16, see Section 2.14 and Section 8.0 for