Yaskawa GPD506/P5 with Apogee FLN Option - Manual (Page 21)

20
4.5 Defining a New Slope & Intercept
Each analog point is defined with a default slope and intercept which scales data to its default units.
Often, a user may want to change these units to be consistent with the control variables of a system. A
common conversion for this drive is to convert frequency data points to a new reference unit.
Unit conversion is accomplished by “unbundling” a point and defining a new slope and intercept. The
following example illustrates how this is done:
1. A drive is installed in a pumping application and must maintain water pressure to a control point
defined in inches of water. The differential pressure sensor has a range of ± 2.5 inches of
water.
2. Frequency command (#60) controls the drive setpoint in hertz, with a default slope of 0.1 and
intercept of 0. The default range of this point is 0 – 60 hertz. An unbundled point can be
added with a slope and intercept defined to convert this range to
± 2.5 inches of water:
• The intercept of the unbundled point is the low end of the new range, or –2.5.
• The slope of the unbundled point is calculated as follows:
Using these values, the unbundled point can be commanded over the range of
±2.5, and the control
system will convert the values into the 0 – 60 hertz range for the drive.
Range) (Current
Slope) (Current Range) (New
Slope New
×
=
0.008333
(60.0)
(0.1) (5.0)
Slope New =
×
=