Transition Measurements (Not in Base Package)

LabVIEW 8.2 Help
August 2006

NI Part Number:
371361B-01

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Accepts an input signal of a single waveform or an array of waveforms and measures the transition duration (rise or fall time), slew rate, preshoot, and overshoot of a selected positive or negative transition in each waveform. The data type you wire to the signal in input determines the polymorphic instance to use. Example

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

Transition Measurements 1 chan

edge number specifies the transition to measure. An edge number of n with rising polarity selected indicates that the VI measures the n^th rising transition it detects in the input waveform.

signal in is the waveform to measure. The waveform is required to contain at least edge number transitions in the direction specified by polarity. A rising transition is the interval between adjacent rising low ref level and high ref level crossings. A falling transition is the interval between adjacent falling high ref level and low ref level crossings.

polarity specifies the direction of the transition to measure as rising (default) or falling.

reference levels specifies the high and low reference levels required to determine the transition interval. mid ref level is not used in transition measurements. Reference levels provide a means to identify the position in time of the waveform feature measured.

	high ref level specifies the high reference level of the waveform in percent (default) or absolute units. A rising high ref level crossing defines the end of a rising transition and a falling high ref level crossing defines the beginning of a falling transition.
	mid ref level specifies the middle reference level in percent (default) or absolute units. mid ref level is not used in transition measurements.
	low ref level specifies the low reference level of the waveform in percent (default) or absolute units. A rising low ref level crossing defines the beginning of a rising transition and a falling low ref level crossing defines the end of a falling transition.
	ref units specifies whether the high ref level, mid ref level, and low ref level inputs are interpreted as a percentage (default) of the full range of the waveform or as absolute levels.

error in describes error conditions that occur before this VI or function runs. The default is no error. If an error occurred before this VI or function runs, the VI or function passes the error in value to error out. This VI or function runs normally only if no error occurred before this VI or function runs. If an error occurs while this VI or function runs, it runs normally and sets its own error status in error out. Use the Simple Error Handler or General Error Handler VIs to display the description of the error code. Use error in and error out to check errors and to specify execution order by wiring error out from one node to error in of the next node.

	status is TRUE (X) if an error occurred before this VI or function ran or FALSE (checkmark) to indicate a warning or that no error occurred before this VI or function ran. The default is FALSE.
	code is the error or warning code. The default is 0. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code.
	source specifies the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning. The default is an empty string.

percent level settings specifies the method used to determine the high and low state levels of a waveform. percent level settings determines the reference levels when percent ref units is selected, otherwise this input is ignored.

method specifies how the high and low state levels of the waveform are computed.

0	Histogram—Returns the levels of the histogram bins with the maximum number of hits in the upper and lower regions of the waveform. The upper and lower regions of the waveform include the upper and lower 40%, respectively, of the waveform's peak-to-peak range.
1	Peak—Searches the entire waveform for its maximum and minimum levels.
2	Auto select—(Default) Determines if the histogram bins corresponding to the high and low state levels each have over 5% of the total hits. If so, it returns those results, otherwise, it uses the peak method. This ensures a reasonable answer for either a square wave (ignoring the overshoot and preshoot) or a triangle wave (where a histogram fails).

histogram size specifies the number of bins in the histogram used to determine the high and low state levels of the waveform. histogram size is ignored if the peak method is selected.

histogram method specifies how the high and low state levels of the waveform are computed. Currently, mode is the only histogram method available.

Mode

reserved is reserved for future use.

slew rate is a measure of the rate of change of the signal in a transition region between high ref level and low ref level. slew rate is given by the following equation.

where transition duration is the transition duration for either rising or falling transition polarity and high ref level and low ref level are in absolute units.

duration is the time span from when the waveform crosses the low ref level until it crosses the high ref level in seconds for a rising transition polarity. The measurement starts at the left edge of the waveform and finds all low ref level crossings preceding the first high ref level crossing. The final low ref level crossing is used in the calculation. A rising polarity transition duration is known as rise time, and a falling polarity transition duration is known as fall time, as shown in the following example:

preshoot measures the height of the local minimum (maximum) preceding a rising (falling) transition as a percentage of the histogram-based amplitude of the signal. If polarity is falling, preshoot is calculated by the following equation.

If polarity is rising, preshoot is calculated by the following equation.

The state levels and amplitude are computed using the histogram method, regardless of the method specified by percent level settings.

The algorithm searches for a local minimum or maximum in a time interval immediately preceding the beginning of the transition specified by edge number and polarity. The interval starts at the middle time between the beginning of the transition specified by edge number and polarity and the end of the preceding transition. If the transition to measure is the first in the waveform, the search interval starts at the beginning of the waveform.

overshoot measures the height of the local maximum (minimum) following a rising (falling) transition as a percentage of the histogram-based amplitude of the signal. If polarity is rising, overshoot is computed by the following equation.

If polarity is falling, overshoot is computed by the following equation.

The state levels and amplitude are computed using the histogram method, regardless of the method specified by percent level settings.

The algorithm searches for a local minimum or maximum in a time interval immediately following the end of the transition specified by edge number and polarity. The interval ends at the middle time between the end of the transition specified by edge number and polarity and the beginning of the following transition. If the transition to measure is the last in the waveform, the search interval ends at the end of the waveform.

error out contains error information. If error in indicates that an error occurred before this VI or function ran, error out contains the same error information. Otherwise, it describes the error status that this VI or function produces. Right-click the error out front panel indicator and select Explain Error from the shortcut menu for more information about the error.

	status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred.
	code is the error or warning code. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code.
	source describes the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning.

measurement info returns the transition interval endpoints and the absolute reference levels used to define the transition.

start time specifies the time of the rising (falling) low (high) ref level crossing that defines the start of the transition to be measured.

end time specifies the time of the rising (falling) high (low) ref level crossing that defines the end of the transition to be measured.

ref levels returns the three user-defined reference levels of the waveform in absolute units. The reference levels are used to define the one cycle measurement interval.

	high ref level returns the high reference level.
	mid ref level returns the middle reference level.
	low ref level returns the low reference level.
	ref units is always absolute in measurement info.

Transition Measurements N chan

signal(s) in is the array of waveforms to measure. The waveform is required to contain at least edge number transitions in the direction specified by polarity. A rising transition is the interval between adjacent rising low ref level and high ref level crossings. A falling transition is the interval between adjacent falling high ref level and low ref level crossings.

polarity specifies the direction of the transition to measure as rising (default) or falling.

	high ref level specifies the high reference level of the waveform in percent (default) or absolute units. A rising high ref level crossing defines the end of a rising transition and a falling high ref level crossing defines the beginning of a falling transition.
	mid ref level specifies the middle reference level in percent (default) or absolute units. mid ref level is not used in transition measurements.
	low ref level specifies the low reference level of the waveform in percent (default) or absolute units. A rising low ref level crossing defines the beginning of a rising transition and a falling low ref level crossing defines the end of a falling transition.
	ref units specifies whether the high ref level, mid ref level, and low ref level inputs are interpreted as a percentage (default) of the full range of the waveform or as absolute levels.

	status is TRUE (X) if an error occurred before this VI or function ran or FALSE (checkmark) to indicate a warning or that no error occurred before this VI or function ran. The default is FALSE.
	code is the error or warning code. The default is 0. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code.
	source specifies the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning. The default is an empty string.

method specifies how the high and low state levels of the waveform are computed.

0	Histogram—Returns the levels of the histogram bins with the maximum number of hits in the upper and lower regions of the waveform. The upper and lower regions of the waveform include the upper and lower 40%, respectively, of the waveform's peak-to-peak range.
1	Peak—Searches the entire waveform for its maximum and minimum levels.
2	Auto select—(Default) Determines if the histogram bins corresponding to the high and low state levels each have over 5% of the total hits. If so, it returns those results, otherwise, it uses the peak method. This ensures a reasonable answer for either a square wave (ignoring the overshoot and preshoot) or a triangle wave (where a histogram fails).

histogram size specifies the number of bins in the histogram used to determine the high and low state levels of the waveform. histogram size is ignored if the peak method is selected.

histogram method specifies how the high and low state levels of the waveform are computed. Currently, mode is the only histogram method available.

Mode

reserved is reserved for future use.

slew rate is an array containing the slew rate for each waveform in signal(s) in. slew rate is a measure of the rate of change of the signal in a transition region between high ref level and low ref level. slew rate is given by the following equation.

where transition duration is the transition duration for either rising or falling transition polarity and high ref level and low ref level are in absolute units.

duration is an array of the time spans from when each waveform crosses the low ref level until it crosses the high ref level in seconds for a rising transition polarity. The measurement starts at the left edge of the waveform and finds all low ref level crossings preceding the first high ref level crossing. The final low ref level crossing is used in the calculation. A rising polarity transition duration is known as rise time, and a falling polarity transition duration is known as fall time, as shown in the following example:

preshoot is an array containing the preshoot for each waveform in signal(s) in. preshoot measures the height of the local minimum (maximum) preceding a rising (falling) transition as a percentage of the histogram-based amplitude of the signal. If polarity is falling, preshoot is calculated by the following equation.

If polarity is rising, preshoot is calculated by the following equation.

The state levels and amplitude are computed using the histogram method, regardless of the method specified by percent level settings.

overshoot is an array containing the overshoot for each waveform in signal(s) in. overshoot measures the height of the local maximum (minimum) following a rising (falling) transition as a percentage of the histogram-based amplitude of the signal. If polarity is rising, overshoot is computed by the following equation.

If polarity is falling, overshoot is computed by the following equation.

The state levels and amplitude are computed using the histogram method, regardless of the method specified by percent level settings.

	status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred.
	code is the error or warning code. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code.
	source describes the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning.

measurement info is an array of clusters containing measurement information for each input waveform.

start time specifies the time of the rising (falling) low (high) ref level crossing that defines the start of the transition to be measured.

end time specifies the time of the rising (falling) high (low) ref level crossing that defines the end of the transition to be measured.

ref levels returns the three user-defined reference levels of the waveform in absolute units. The reference levels are used to define the one cycle measurement interval.

	high ref level returns the high reference level.
	mid ref level returns the middle reference level.
	low ref level returns the low reference level.
	ref units is always absolute in measurement info.

Example

Refer to the Pulse and Transition Measurements VI in the labview\examples\measure\maxmpl.llb for an example of using the Transition Measurements VI.

Transition Measurements (Not in Base Package)

Transition Measurements 1 chan

Transition Measurements N chan

Example

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