Rockwell Automation 8720MC Drives Integration Manual - Manual (Page 43)

Publication 8720MC-IN002A-EN-P — December 2002
Commissioning Your 8720MC Analog Drive 2-11
Analog Inputs and Outputs
The 8720MC has two ±10V dc analog outputs and two ±10V dc analog
inputs. The analog inputs are only available in the analog input
spindle or power servo software configurations (parameter 501). In
the SERCOS configuration the analog inputs are used to interface to
the auxiliary, spindle, or axis mounted feedback device that is
connected to the auxiliary feedback connector. In the analog input
spindle or power servo software configurations (as determined by
parameter 501) analog input 1 provides the torque or velocity
command reference to the drive. Analog input 2 provides a manual
velocity reference for manual operator stations. Figure 2.1 illustrates
the recommended connections for the analog inputs and outputs.
Refer to Appendix C for a description of the analog input parameters
(analog inputs 1 and 2) under parameters 691 to 692. Each analog
input has a scaling factor associated with it, parameters 695 and 696.
Refer to Appendix C for details on how to use the scaling parameters
with the analog inputs. The default velocity scaling is 100 rpm/volt for
both analog input 1 and 2. As an example, assume the motion
controller is scaled such that 8 volts produces a maximum speed of
6,000 rpm. The drive should also be scaled such that 8 volts equals
6,000 rpm. This is accomplished by using a scaling factor value of 750
rpm/volt or a value of 7500 in parameter 695. The A/D resolution is
±8192 bits or 1.2 mv/bit, based on a ±10 volt input command. It is
always best to use the full ±10 Volt range so that maximum velocity
resolution is achieved. When in torque mode the scaling factor for
analog input 1 is fixed at 2.5 volts = 100% continuous rated torque.