DC Offset

Part number 9620


DC Offset Control allows the COLA output to be used as a secondary control loop to control the DC offset of a select input channel.


The Control Channel specifies the channel to use for closed loop control. This input must be configured as a DC input and also have the same unit category as the DC signal.

The Proportional and Integral parameters are used to tune the PI control loop. The Motor Controls dialog is part of the optional motor simulator package. Note that if the DC Reference unit is not configured as a rotational velocity or a frequency unit, this dialog will be titled “DC Offset.”

DC Offset Reference allows the COLA to output an open loop DC voltage proportional to a configured engineering unit, with the desired output level configured on a per-schedule-level basis within the test settings ‘Schedule’ tab.

The DC Offset parameters control the functionality of the DC Offset Reference and DC Offset Control options. The units and volts entry boxes allow the scaling factor for the DC output to be entered.

The Slew Rate (On) and Slew Rate (Off) parameters specify how fast the DC signal is allowed to change.

The Superimpose Drive Signal option will superimpose the drive signal over top of the DC signal. This allows you to have a DC signal and an AC signal on the same output. This can be useful for driving a shaker and giving it a DC offset. Note that this happens after the DC limits have been tested. If you have this option set, it is possible that the COLA will output a voltage level greater than the limits specified for Max Output or Min Output.

The Max Output and Min Output limits the DC voltage level the COLA will output. Note that this limit is performed before the drive signal is superimposed. If the drive signal is superimposed, it is possible that the specified voltage level will be exceeded. If the Abort when limits reached check box is checked, the test will abort when the DC limit is reached. If it is not checked, the test will continue to run but the DC signal will be held to the specified limits.

How Can We Help You?

Contact Us