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Find Transitions VI

LabVIEW 2012 Jitter Analysis Toolkit Help

Edition Date: June 2012

Part Number: 373270B-01

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Owning Palette: Level VIs

Requires: Jitter Analysis Toolkit

Measures the boundaries and directions of each transition in a waveform given the reference levels you specify. Wire data to the waveform input to determine the polymorphic instance to use or manually select the instance.

Refer to the Details section of this topic for more information about how this VI identifies transitions.

You can use the transition information this VI generates to perform measurements such as the overshoot, rise time, and fall time of waveform transitions.

Details  Examples

Use the pull-down menu to select an instance of this VI.

Find Transitions (DBL)

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.
transitions returns information about the transitions in the waveform.
transition is an array of clusters that describe the boundaries and direction of each transition in waveform.
start index is the index of the sample at which the signal crosses the high ref level or low ref level and the transition begins.

If the slope of the transition is Rising Edge, the start index is where the signal crosses the low ref level. If the slope is Falling Edge, the start index is where the signal crosses the high ref level.
end index is the index of the sample at which the signal crosses the high ref level or low ref level and the transition ends.

If the slope of the transition is Rising Edge, the end index is where the signal crosses the high ref level. If the slope is Falling Edge, the end index is where the signal crosses the low ref level.
slope returns whether the direction of the transition is rising or falling.

-1Falling Edge—The transition is a falling edge, or one with a negative slope.
1Rising Edge (default)—The transition is a rising edge, or one with a positive slope.
state levels returns the state level information from the waveform.
amplitude is the difference between high state level and low state level.
high state level returns the level at which a pulse or transition waveform is defined to be in its highest state.
low state level returns the level at which a pulse or transition waveform is defined to be in its lowest state
ref levels returns the three reference levels of the waveform in absolute units. LabVIEW uses the reference levels to define the interval of one cycle measurement.
high ref level returns the high reference level.
mid ref level returns the middle reference level.
low ref level returns the low reference level.
error out contains error information. This output provides standard error out functionality.

Find Transitions (I8)

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.
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.
transitions returns information about the transitions in the waveform.
transition is an array of clusters that describe the boundaries and direction of each transition in waveform.
start index is the index of the sample at which the signal crosses the high ref level or low ref level and the transition begins.

If the slope of the transition is Rising Edge, the start index is where the signal crosses the low ref level. If the slope is Falling Edge, the start index is where the signal crosses the high ref level.
end index is the index of the sample at which the signal crosses the high ref level or low ref level and the transition ends.

If the slope of the transition is Rising Edge, the end index is where the signal crosses the high ref level. If the slope is Falling Edge, the end index is where the signal crosses the low ref level.
slope returns whether the direction of the transition is rising or falling.

-1Falling Edge—The transition is a falling edge, or one with a negative slope.
1Rising Edge (default)—The transition is a rising edge, or one with a positive slope.
state levels returns the state level information from the waveform.
amplitude is the difference between high state level and low state level.
high state level returns the level at which a pulse or transition waveform is defined to be in its highest state.
low state level returns the level at which a pulse or transition waveform is defined to be in its lowest state
ref levels returns the three reference levels of the waveform in absolute units. LabVIEW uses the reference levels to define the interval of one cycle measurement.
high ref level returns the high reference level.
mid ref level returns the middle reference level.
low ref level returns the low reference level.
error out contains error information. This output provides standard error out functionality.

Find Transitions Details

This VI identifies transition boundaries by locating a level crossing in the waveform, and then finding the nearest reference level crossing on each side of the crossing. In other words, this VI identifies transitions as in the following descriptions:

  • This VI identifies falling transitions by finding all portions of the waveform that cross the high reference level and then cross the low reference level from above with no other high or low reference crossings in between.
  • This VI identifies rising transitions by finding all portions of the waveform that cross the low reference level and then cross the high reference level from below with no other high or low reference crossings in between.

Examples

Refer to the following VIs for examples of using the Find Transitions VI:

  • Mask and Limit Test VI: labview\examples\Jitter Analysis\Eye Diagram Measurements
  • Overshoot Demo VI: labview\examples\Jitter Analysis\Level Measurements

 

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