Control DC Offset of an Input Channel
DC Offset Control allows the COLA output on the VR9500/VR10500 to function as a secondary control loop. In doing so, the user can control the DC offset of a selected input channel.
The user can specify which channel to use for closed-loop control. The input must be configured as a DC input and have the same unit category as the DC signal.
The COLA output provides a voltage sync signal to external equipment. Aside from DC Offset Control, the COLA output can be differential, sine, or square, or can function as a DC frequency reference, a phase-controlled second output for multi-axis testing, or control only.
VR Controller Hardware
VR9500 I/O Unit
Vibration Research’s best-selling control hardware for vibration and shock testing. Scalable to 128 channels and compatible with all electrodynamic and servo-hydraulic shakers. Features include up to 200kHz sample rate and 2 outputs.
VR10500 I/O Unit
Vibration Research’s high channel count control hardware for vibration and shock testing. Scalable to 512 channels and compatible with all electrodynamic and servo-hydraulic shakers. Features include up to 256kHz sample rate and 4 outputs for multiple shakers.
DC Offset Parameters
The DC Offset parameters control the functionality of DC Offset Control. The user can define the scaling factor for the DC output using the units and Volts parameters. The parameters also control the DC Offset Reference option.
DC Offset Reference
The DC Offset parameters also control the DC Offset Reference option. DC Offset Reference uses the COLA to output an open loop DC voltage proportional to a user-configured engineering unit. The desired output level is configured on a per schedule level basis within the test settings.
What is a Closed Loop?
The COLA output is not active until the system detects a closed-loop response between the drive output and the control input channel. In a closed-loop system, the vibration controller sends an input through an amplifier to the shaker. A transducer then sends the output of the device under test (DUT) back to the controller. The system monitors and adjusts the actual output based on the desired parameters.
DC Offset Control for Amature Centering
Define Motor Operation
With the optional motor simulator package, the user can define motor operation in Sine. The user can enable, disable, or phase lock the angular velocity and set the phase value (degrees).
Enabling the angular velocity brings the motor to the user-specified level. If the COLA is configured as DC Offset Reference or DC Offset Control, it will output a DC signal proportional to the user-specified value. The user can also configure a sine sweep by defining differing Start and End levels and a sweep rate.
The Phase Lock option enables the output and locks the phase between the drive signal and the external motor to the user-specified phase value. The Disable option will disable the motor and prevent the COLA from sending a DC signal.