Rockwell Automation 20B PowerFlex 70, PowerFlex 700 Reference Manual - Manual (Page 22)

Analog Inputs
22 Rockwell Automation Publication PFLEX-RM001H-EN-P - June 2013
Analog Scaling
[Analog In Hi]
[Analog In 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]
Configuration #1:
•
[Anlg In Config], bit 0 = “0” (Voltage)
•
[Speed Ref A Sel] = “Analog In 1”
•
[Speed Ref A Hi] = 60 Hz
•
[Speed Ref A Lo] = 0 Hz
•
[Analog In 1 Hi] = 10V
•
[Analog In 1 Lo] = 0V
This is the default setting, where minimum input (0 volts) represents 0 Hz and
maximum input (10 volts) represents 60 Hz (it provides 6 Hz change per input
volt).