Level Crossing VI

Owning Palette: Timing VIs

Requires: Jitter Analysis Toolkit

Measures the times and locations a waveform crosses a particular voltage level. The Jitter Analysis VIs use level crossings to identify a common position in all transitions that you can use for comparison. Wire data to the transitions input and the waveform input to determine the polymorphic instance to use or manually select the instance.

This VI uses linear interpolation of the waveform points in transition regions to locate the precise crossing times. If the signal crosses the level more than once in a transition region, this VI returns only the first crossing.

Examples

Level Crossing (Transitions in, DBL)

Use this polymorphic instance to identify the level crossings in a waveform from information about its transitions.

This instance operates on the waveform data type when the Y data values are double-precision, floating-point numeric values. Use the I8 instance of this VI with integer data to reduce the size of the data and the memory usage.

	waveform is the waveform to measure. t0 specifies the start time of the waveform. dt specifies the time interval in seconds between data points in the waveform. Y specifies the data values of the waveform.
	transitions contains information about the transitions in the waveform. Use the Find Transitions VI to generate this cluster. transition is an array of clusters that describe each transition in waveform. start index specifies the sample of waveform at which the transition begins. end index specifies the sample of waveform at which the transition ends. slope identifies the direction of the first transition in the waveform. -1 Falling Edge—Specifies the transition is a falling edge, or one with a negative slope. 1 Rising Edge (default)—Specifies the transition is a rising edge, or one with a positive slope. state levels specifies the high and low state values in the waveform and the corresponding amplitude. amplitude is the difference between high state level and low state level. high state level specifies the level at which a pulse or transition waveform is defined to be in its highest state. low state level specifies the level at which a pulse or transition waveform is defined to be in its lowest state ref levels specifies the high, middle, and low reference levels of a waveform. high ref level specifies the high reference level of the waveform in absolute units. mid ref level specifies the middle reference level of the waveform in absolute units. low ref level specifies the low reference level as a percentage (default) or in absolute units. The default is 10.00.
	crossing level specifies the value at which this VI identifies level crossings in the waveform. If you do not wire a crossing level value, LabVIEW uses the mid reference level of the waveform.
	error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
	waveform dup returns waveform unchanged.
	level crossings returns information about the locations of level crossings in the waveform. t0 returns the time at which the first sample occurred in the original waveform. dt returns the time interval in seconds between the individual samples in the original waveform. indexes contains the index numbers of waveform samples that fall on the crossing level and whose transition crosses both the high and low reference levels. slope returns whether the direction of the first transition in the waveform is rising or falling -1 Falling Edge—The transition is a falling edge, or one with a negative slope. 1 Rising Edge—The transition is a rising edge, or one with a positive slope. crossing level returns the input crossing level value at which the waveform falls at each sample in indexes.
	error out contains error information. This output provides standard error out functionality.

Level Crossing (Transitions in, I8)

Use this polymorphic instance to identify the level crossings in a waveform from information about its transitions.

This instance operates on the waveform data type when the Y data values are 8-bit signed integers.

	waveform is the waveform to measure. t0 specifies the start time of the waveform. dt specifies the time interval in seconds between data points in the waveform. Y specifies the data values of the waveform.
	transitions contains information about the transitions in the waveform. Use the Find Transitions VI to generate this cluster. transition is an array of clusters that describe each transition in waveform. start index specifies the sample of waveform at which the transition begins. end index specifies the sample of waveform at which the transition ends. slope identifies the direction of the first transition in the waveform. -1 Falling Edge—Specifies the transition is a falling edge, or one with a negative slope. 1 Rising Edge (default)—Specifies the transition is a rising edge, or one with a positive slope. state levels specifies the high and low state values in the waveform and the corresponding amplitude. amplitude is the difference between high state level and low state level. high state level specifies the level at which a pulse or transition waveform is defined to be in its highest state. low state level specifies the level at which a pulse or transition waveform is defined to be in its lowest state ref levels specifies the high, middle, and low reference levels of a waveform. high ref level specifies the high reference level of the waveform in absolute units. mid ref level specifies the middle reference level of the waveform in absolute units. low ref level specifies the low reference level as a percentage (default) or in absolute units. The default is 10.00.
	crossing level specifies the value at which this VI identifies level crossings in the waveform. If you do not wire a crossing level value, LabVIEW uses the mid reference level of the waveform.
	error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
	waveform dup returns waveform unchanged.
	level crossings returns information about the locations of level crossings in the waveform. t0 returns the time at which the first sample occurred in the original waveform. dt returns the time interval in seconds between the individual samples in the original waveform. indexes contains the index numbers of waveform samples that fall on the crossing level and whose transition crosses both the high and low reference levels. slope returns whether the direction of the first transition in the waveform is rising or falling -1 Falling Edge—The transition is a falling edge, or one with a negative slope. 1 Rising Edge—The transition is a rising edge, or one with a positive slope. crossing level returns the input crossing level value at which the waveform falls at each sample in indexes.
	error out contains error information. This output provides standard error out functionality.

Level Crossing (Levels in, DBL)

Use this polymorphic instance to identify the level crossings in a waveform from its state levels and reference levels. This instance uses the mid ref level as the crossing level.

This instance operates on the waveform data type when the Y data values are double-precision, floating-point numeric values. Use the I8 instance of this VI with integer data to reduce the size of the data and the memory usage.

	waveform is the waveform to measure. t0 specifies the start time of the waveform. dt specifies the time interval in seconds between data points in the waveform. Y specifies the data values of the waveform.
	state levels specifies the high and low state values in the waveform and the corresponding amplitude. You can use the State Levels or Reference Levels VIs to generate this cluster. amplitude is the difference between high state level and low state level. high state level specifies the level at which a pulse or transition waveform is defined to be in its highest state. low state level specifies the level at which a pulse or transition waveform is defined to be in its lowest state
	reference levels specifies the high, middle, and low reference levels of a waveform. You can use the Reference Levels VI to generate this cluster. high ref level specifies the high reference level of the waveform in absolute units. mid ref level specifies the middle reference level of the waveform in absolute units. low ref level specifies the low reference level as a percentage (default) or in absolute units. The default is 10.00.
	error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
	waveform dup returns waveform unchanged.
	level crossings returns information about the locations of level crossings in the waveform. t0 returns the time at which the first sample occurred in the original waveform. dt returns the time interval in seconds between the individual samples in the original waveform. indexes contains the index numbers of waveform samples that fall on the crossing level and whose transition crosses both the high and low reference levels. slope returns whether the direction of the first transition in the waveform is rising or falling -1 Falling Edge—The transition is a falling edge, or one with a negative slope. 1 Rising Edge—The transition is a rising edge, or one with a positive slope. crossing level returns the input crossing level value at which the waveform falls at each sample in indexes.
	error out contains error information. This output provides standard error out functionality.

Level Crossing (Levels in, I8)

Use this polymorphic instance to identify the level crossings in a waveform from its state levels and reference levels. This instance uses the mid ref level as the crossing level.

This instance operates on the waveform data type when the Y data values are 8-bit signed integers.

	waveform is the waveform to measure. t0 specifies the start time of the waveform. dt specifies the time interval in seconds between data points in the waveform. Y specifies the data values of the waveform.
	transitions contains information about the transitions in the waveform. Use the Find Transitions VI to generate this cluster. transition is an array of clusters that describe each transition in waveform. start index specifies the sample of waveform at which the transition begins. end index specifies the sample of waveform at which the transition ends. slope identifies the direction of the first transition in the waveform. -1 Falling Edge—Specifies the transition is a falling edge, or one with a negative slope. 1 Rising Edge (default)—Specifies the transition is a rising edge, or one with a positive slope. state levels specifies the high and low state values in the waveform and the corresponding amplitude. amplitude is the difference between high state level and low state level. high state level specifies the level at which a pulse or transition waveform is defined to be in its highest state. low state level specifies the level at which a pulse or transition waveform is defined to be in its lowest state ref levels specifies the high, middle, and low reference levels of a waveform. high ref level specifies the high reference level of the waveform in absolute units. mid ref level specifies the middle reference level of the waveform in absolute units. low ref level specifies the low reference level as a percentage (default) or in absolute units. The default is 10.00.
	crossing level specifies the value at which this VI identifies level crossings in the waveform. If you do not wire a crossing level value, LabVIEW uses the mid reference level of the waveform.
	error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
	waveform dup returns waveform unchanged.
	level crossings returns information about the locations of level crossings in the waveform. t0 returns the time at which the first sample occurred in the original waveform. dt returns the time interval in seconds between the individual samples in the original waveform. indexes contains the index numbers of waveform samples that fall on the crossing level and whose transition crosses both the high and low reference levels. slope returns whether the direction of the first transition in the waveform is rising or falling -1 Falling Edge—The transition is a falling edge, or one with a negative slope. 1 Rising Edge—The transition is a rising edge, or one with a positive slope. crossing level returns the input crossing level value at which the waveform falls at each sample in indexes.
	error out contains error information. This output provides standard error out functionality.

Examples

Refer to the following VIs for examples of using the Level Crossing VI:

• Basic Eye Diagram VI: labview\examples\Jitter Analysis\Eye Diagram Measurements
• Rj Dj Separation VI: labview\examples\Jitter Analysis\Jitter Measurements
• Simulated Signal with Jitter VI: labview\examples\Jitter Analysis\Jitter Measurements