User Manual Instruction Manual

Application Notes 13-45
13.19.3 Analog Scaling
Analog In x Hi
Analog In x Lo
A scaling operation is performed on the value read from an analog input in order to
convert it to units usable for some particular purpose. The user controls the scaling by
setting parameters that associate a low and high point in the input range (i.e. in volts
or mA) with a low and high point in the target range (e.g. reference frequency).
Two sets of numbers may be used to specify the analog input scaling. One set (called
the “input scaling points”) defines low and high points in terms of the units read by the
input hardware, i.e. volts or mA.
The second set of numbers (called the “output scaling points”) used in the analog
input scaling defines the same low and high points in units appropriate for the desired
use of the input. For instance, if the input is to be used as a frequency reference, this
second set of numbers would be entered in terms of Hz. For many features the
second set of numbers is fixed. The user sets the second set for speed and reference
trim.
An analog input or output signal can represent a number of different commands.
Typically an analog input is used to control output frequency, but it could control
frequency trim, current limit or act as a PI loop input. An analog output typically is a
frequency indication, but it could represent output current, voltage, or power. For this
reason this document defines an analog signal level as providing a “command” value
rather than a “frequency.” However when viewing a command value it is presented as
a frequency based on the [Minimum Speed] and [Maximum Freq] settings.
The 0-10 volt input scaling can be adjusted using the following parameters:
• Analog In x Lo
• Analog In x Hi
13.19.3.1 Configuration #1:
• Anlg In Config (320), bit 0 = “0” (Voltage)
• Speed Ref A Sel (90) = “Analog In 1”
• Speed Ref A Hi (91) = 60 Hz
• Speed Ref A Lo (92) = 0 Hz
• Analog In 1 Hi (322) = 10V
• Analog In 1 Lo (323) = 0V