System 450™ Series Modular Control Systems with Standard Control Modules Technical Bulletin
59
Note:
The direction of the voltage changes (rise or drop) depends on whether
the analog output is set up as a direct acting or reverse acting output
signal. These instructions refer to the room heating application example
shown in Figure 27.
4. Observe the system response and record the time it takes for the measured
voltage to drive to and stabilize at the shifted control point in the shifted
proportional band. (Typically the shifted control point voltage is slightly higher
[or lower] than the original control point voltage.)
5. With the controlled system stabilized at the shifted control point, return
(second step change) the Setpoint and End Point values back to the original
proportional band. The signal VDC drops (or rises) immediately and
significantly in response to the proportional band shift back to original. Begin
timing the response (to the second step change) at this voltage drop (or rise).
6. Observe the system response and record the time it takes for the measured
voltage to drive back to and stabilize at original control point (voltage) in the
original proportional band.
Figure 27: Graph Showing Temporary Proportional Band and Control
Point Shifts Used to Measure Response Time in a Heating Application
66°F
SP
EP
70°F
Proportional
Band
67°F
Sh
ifte
d
EP
71°F
Sh
ifte
d
SP
0%
100%
Shifted
Control Point
Measure the (first response) time that it takes for the controlled system to drive from the original control point
to the shifted control point and then measure the (
) time for the system to drive from
the shifted control point back to the original control point. Use the slower response to determine the proper I-C.
second response
10 VDC
0 VDC
An
al
og
O
utpu
t V
olta
ge
Sy
st
em
O
ut
put
Original
Control Point
Condition Value
(and Time)
VDC
Rise
F
ig:
sys
4
50
_c
n
tr
l_
po
nt
_s
h
ft
