Shape the variation in a value over time (ratio or ramp function). The resulting ramp can have a maximum of two curves.
RAMP translates an input into a proportional output based on a set of user-defined curves.
Fig. 232. Wire-sheet Icon
Fig. 233. Property Sheet
Fig. 234. Slot Sheet
Table 145. Inputs
Inputs |
Type |
Functional description |
In Ramp |
numeric |
Input value |
In Enabled |
boolean |
If the input “In Enabled” is set to false disabled in the slot sheet, the output “Out” will be disabled and is set to the value “0”. |
Table 146. Outputs
Outputs |
Type |
Functional description |
Out Ramp |
numeric |
Analog output signal |
Table 147. Parameter List
Description |
Value Range |
Default Value |
Unit |
P1 Ymin minimum output value |
-∞...∞ |
0 |
- |
P2 Ymax maximum output value |
-∞...∞ |
100 |
- |
P3 Xmin minimum input value |
-∞...∞ |
0 |
- |
P4 Xmax maximum input value |
-∞...∞ |
100 |
- |
P5 Xa minimum input value of the first ramp |
-∞...∞ |
0 |
- |
P6 Ya minimum output value of the first ramp |
-∞...∞ |
0 |
- |
P7 Xb maximum input value of the first ramp |
-∞...∞ |
50 |
- |
P8 Xc second minimum input value of the second ramp |
-∞...∞ |
50 |
- |
P9 Ybc maximum output value of the first ramp minimum output value of the second ramp |
-∞...∞ |
50 |
- |
P10 Xd maximum input value of the second ramp |
-∞...∞ |
100 |
- |
P11 Yd maximum output value of the second ramp |
-∞...∞ |
100 |
- |
The parameters dialog box allows you to define the two curves graphically. In the following example, the first curve is selected, that is, there is an empty area within the two axes outlined by a box. This box is where the first curve appears as you define the ranges for the Ya, Yb, Xa, and Xb variables.
Fig. 235. Ramp dialog box
Use the following procedure to create two curves for the desired “Out Ramp” output.
Relative humidity like compensated setpoint
The following diagram shows how the software interprets the graph.
Fig. 236. Ramp dialog box example 2
Scale Changes
When you change the minimum and maximum X and Y scale values, the Ramp statement adjusts the minimum and maximum values for the curves so that they are not outside the overall X and Y ranges.
For example, assume an application has the following values:
Y scale ranges from 0 through 100 (Ymin through Ymax)
X scale ranges from 0 through 100 (Xmin through Xmax)
Curve 1 X scale ranges from 20 through 40 (Xa through Xb)
Y scale ranges from 25 through 80 (Ya through Ybc)
Curve 2 X scale ranges from 65 through 85 (Xc through Xd
Y scale ranges from 80 through 55 (Ybc through Yd)
Fig. 237. Ramp dialog box example 2
If you increase the minimum on the Y scale from 0 to 30, Ramp changes the Y scale minimum for Curve 1 from 25 to 30 so that the curve stays within the minimum and maximum Y scale range.
Fig. 238. Ramp dialog box example 2 rescaling the Ymin value
If you decrease the maximum on the Y scale from 100 to 60, RAMP changes the Y scale maximum for Curve 1 from 80 to 60 (within the overall Y-scale range). Ramp also changes the Y scale minimum for Curve 2 from 80 to 60 for the same reason.
Fig. 239. Ramp dialog box example 2 rescaling the Ymax value
Ramp Example
This example shows a room temperature setpoint with winter and summer compensation:
Fig. 240. Compensated setpoint with Ramp connected to a PID controller
Set Ymin, Ymax, Xmin, and Xmax to determine the scale limits.
Fig. 241. Compensated setpoint with winter and summer compensation
Winter compensation:
OAT room temp. setpoint
Xa -5 Ya 22
Xb 20 Ybc 20
Summer compensation:
OAT room temp. setpoint
Xc 20 Ybc 20
Xd 25 Yd 22