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Overshoot and Undershoot 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 times, locations, and amounts by which a waveform rises above and falls below a state level before or after a transition. The rise above a state level is known as overshoot, and the drop below a state level is known as undershoot. Wire data to the waveform input to determine the polymorphic instance to use or manually select the instance.

Note  The terminology and measurement definitions for this VI comply with IEEE Standard 181-2003, IEEE Standard on Transitions, Pulses, and Related Waveforms.

Details  Example

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

Overshoot and Undershoot (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.
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.

-1Falling Edge—Specifies the transition is a falling edge, or one with a negative slope.
1Rising 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.
transition select sets whether to identify overshoot and undershoot in the regions before or after each transition.

0pre-transition—Specifies to return measurements from the regions that precede transitions.
1post-transition (default)—Specifies to return measurements from the regions that follow transitions.
error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
slope specifies the direction of the transitions for which you want to return measurements.

-1Falling Edge—Returns information about falling edges, or those with negative slopes.
0Both—Returns information about both rising and falling edges.
1Rising Edge (default)—Returns information about rising edges, or those with positive slopes.
overshoot sequence returns an array of the overshoot values for local maximums associated with the types of transitions you specify using slope and transition select. Overshoot measures the height as a fraction of the amplitude of the signal. Refer to the Details section of this topic for more information about how this VI calculates overshoot.
overshoot timestamps returns timing information about the waveform that allows you to identify the times at which measurements in the corresponding sequence occur.
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 the samples in the waveform measured as overshoot. Each element of indexes corresponds to an element of overshoot sequence.
undershoot sequence returns an array of the undershoot values for local minimums associated with the types of transitions you specify using slope and transition select. Undershoot measures the height as a fraction of the amplitude of the signal. Refer to the Details section of this topic for more information about how this VI calculates undershoot.
undershoot timestamps returns timing information about the waveform that allows you to identify the times at which measurements in the corresponding sequence occur.
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 the samples in the waveform measured as undershoot. Each element of indexes corresponds to an element of undershoot sequence.
error out contains error information. This output provides standard error out functionality.

Overshoot and Undershoot (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.
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.

-1Falling Edge—Specifies the transition is a falling edge, or one with a negative slope.
1Rising 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.
transition select sets whether to identify overshoot and undershoot in the regions before or after each transition.

0pre-transition—Specifies to return measurements from the regions that precede transitions.
1post-transition (default)—Specifies to return measurements from the regions that follow transitions.
error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
slope specifies the direction of the transitions for which you want to return measurements.

-1Falling Edge—Returns information about falling edges, or those with negative slopes.
0Both—Returns information about both rising and falling edges.
1Rising Edge (default)—Returns information about rising edges, or those with positive slopes.
overshoot sequence returns an array of the overshoot values for local maximums associated with the types of transitions you specify using slope and transition select. Overshoot measures the height as a fraction of the amplitude of the signal. Refer to the Details section of this topic for more information about how this VI calculates overshoot.
overshoot timestamps returns timing information about the waveform that allows you to identify the times at which measurements in the corresponding sequence occur.
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 the samples in the waveform measured as overshoot. Each element of indexes corresponds to an element of overshoot sequence.
undershoot sequence returns an array of the undershoot values for local minimums associated with the types of transitions you specify using slope and transition select. Undershoot measures the height as a fraction of the amplitude of the signal. Refer to the Details section of this topic for more information about how this VI calculates undershoot.
undershoot timestamps returns timing information about the waveform that allows you to identify the times at which measurements in the corresponding sequence occur.
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 the samples in the waveform measured as undershoot. Each element of indexes corresponds to an element of undershoot sequence.
error out contains error information. This output provides standard error out functionality.

Overshoot and Undershoot Details

The following illustration shows the overshoot and undershoot in a single negative transition.

The following illustration shows the overshoot and undershoot in a single positive transition.

Pre-transition Measurements

To calculate pre-transition overshoot and undershoot for each transition, LabVIEW searches for a local minimum and maximum in the pre-transition aberration region immediately preceding the beginning of the transition. The pre-transition aberration region is defined as the minimum of 3*(end time – start time) and (current transition start time – previous transition end time) / 2. If the transition to measure is the first in the waveform, the interval is defined as the minimum of 3*(end time – start time) and (start time – beginning of the waveform).

If slope is falling, LabVIEW calculates the pre-transition undershoot using the following equation:

If slope is rising, LabVIEW calculates the pre-transition undershoot using the following equation:

If slope is falling, LabVIEW calculates the pre-transition overshoot using the following equation:

If slope is rising, LabVIEW calculates the pre-transition overshoot using the following equation:

where the state levels and amplitude are defined in the transitions input.

Post-transition Measurements

To calculate post-transition undershoot and overshoot for each transition, LabVIEW searches for a local minimum and maximum in the post-transition aberration region immediately following the end of the transition. The post-transition aberration region is defined as the minimum of 3*(end time – start time) and (next transition start time – current transition end time) / 2. If the transition to measure is the last in the waveform, the interval is defined as the minimum of 3*(end time – start time) and (end of the waveform – end time).

If slope is falling, LabVIEW calculates the post-transition undershoot using the following equation:

If slope is rising, LabVIEW calculates the post-transition undershoot using the following equation:

If slope is falling, LabVIEW calculates the post-transition overshoot using the following equation:

If slope is rising, LabVIEW calculates the post-transition overshoot using the following equation:

where the state levels and amplitude are defined in the transitions input.

Example

Refer to the Overshoot Demo VI in the labview\examples\Jitter Analysis\Level Measurements directory for an example of using the Overshoot and Undershoot VI.


 

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