Velocity Threshold (100,000) is the velocity threshold in counts/s (servo axes) or steps/s (stepper axes). For servo axes, the threshold range is 1 to 16,000,000 counts/s. For stepper axes, it is 1 to 1,500,000 steps/s. The factory default value for threshold is the maximum, so the feature is effectively disabled until a threshold is loaded.
	Board ID is a unique number assigned by Measurement & Automation Explorer (MAX) used to send and receive commands and data to or from a specific NI motion controller.
	Axis is the axis to control.
	Inp Vect indicates the source of the data for this VI. Available input vectors include immediate (0xFF), variable (0x01 through 0x78), or indirect variable (0x81 through 0xF8). Refer to Input and Return Vectors for more detailed information.
	error in (no error) describes error conditions that occur before this VI runs. The default input of this cluster is no error. If an error already occurred, this VI returns the value of error in in error out. The VI runs normally only if no incoming error exists. Otherwise, the VI passes the error in value to error out. The error in cluster contains the following parameters: status is TRUE if an error occurred before this VI was called, or FALSE if not. If status is TRUE, code is a nonzero error code. If status is FALSE, code is zero or a warning code. code is a number identifying an error or warning. If status is TRUE, code is a nonzero error code. If status is FALSE, code is zero or a warning code. Use the error handler VIs to look up the meaning of this code and display the corresponding error message. source is a string that indicates the origin of the error, if any. Typically, source is the name of the VI in which the error occurred.
	Bd ID Out is provided for flow control. You can string together NI-Motion VIs by wiring the Bd ID Out terminal of one VI to the Board ID terminal of the next VI.
	Resource Output is the Axis, Vector Space, ADC, or Encoder you wired into the VI. Use Resource Output to pass the resource to another VI and/or to display information about the device.
	error out contains error information. If error in indicates an error, error out contains the same error information. Otherwise, it describes the error status that this VI produces. status is TRUE if an error occurred, or FALSE if not. If status is TRUE, code is a nonzero error code. If status is FALSE, code is zero or a warning code. code is a number identifying an error or warning. If status is TRUE, code is a nonzero error code. If status is FALSE, code is zero or a warning code. Use the error handler VIs to look up the meaning of this code and display the corresponding error message. source is a string that indicates the origin of the error, if any. Typically, source is the name of the VI in which the error occurred.

Using This VI

The Load Velocity Threshold VI establishes a velocity threshold for the specified axis, which can then be monitored with the Read Trajectory Status VI. The velocity threshold status is True when the absolute value of filtered axis velocity is above the threshold and False when the velocity drops below the threshold.

Velocity threshold is a status and does not have to be enabled or disabled. Loading a maximum value effectively disables the feature because the status will always be off. Increasing the velocity filter time constant with the Configure Velocity Filter VI reduces quantization noise in the threshold status but at the expense of increasing threshold status latency.

Velocity threshold is typically used to monitor the acceleration and deceleration trajectory periods to see when or if an axis is up to speed. You can then change PID tuning or other parameters as a function of velocity.

Remarks

This section includes information about how the behavior of this VI differs among the controllers that support it.

NI SoftMotion Controller Considerations

The following list includes considerations you must make when you are using this VI with the NI SoftMotion Controller:

• Use Load Counts/Steps per Revolution to set Counts(Steps)/Rev value to 1. Otherwise, NI-Motion returns an error.