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Pulse Time and Transition Measurements (Transition) (G Dataflow)

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Last Modified: August 6, 2018

Accepts an input signal of a single waveform or an array of waveforms and measures the transition duration, undershoot, and overshoot of a selected positive or negative transition in each waveform.

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signal

The input signal.

This input can be a waveform or an array of waveforms.

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polarity

A value specifying whether to measure a rising or falling transition.

Name Value Description
Rising 0 The node measures a rising transition.
Falling 1 The node measures a falling transition.

Default: Rising

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edge number

The transition to measure. An edge number of n with rising polarity selected indicates that the node measures the nth rising transition it detects in the input waveform.

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reference levels settings

High and low reference levels required to determine the transition interval.

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high ref level

High reference level of the waveform.

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.

Default: 90

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mid ref level

Middle reference level of the waveform.

mid ref level is not used in transition measurements.

Default: 50

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low ref level

Low reference level of the waveform.

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.

Default: 10

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ref units

Units of the high, middle, and low reference levels.

Name Value Description
absolute 0 Interprets the reference levels as absolute levels.
percent 1 Interprets the reference levels as a percentage of the full range of the waveform.

Default: percent

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error in

Error conditions that occur before this node runs.

The node responds to this input according to standard error behavior.

Standard Error Behavior

Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

error in does not contain an error error in contains an error
If no error occurred before the node runs, the node begins execution normally.

If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.

Default: No error

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state levels settings

Settings that determine the high and low state levels of a waveform.

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method

Method this node uses to compute the high and low state levels of the waveform.

Name Description
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 peak-to-peak range of the waveform.
peak Searches the entire waveform for its maximum and minimum levels.
auto select Determines whether the histogram bins that correspond to the high and low state levels each have over 5% of the total hits. If so, this node returns those results. Otherwise, this node uses the peak method. This ensures a reasonable answer for either a square wave (ignoring the overshoot and undershoot) or a triangle wave (where a histogram fails).

Default: auto select

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histogram size

Number of bins in the histogram this node uses to determine the high and low state levels of the waveform.

If you select the peak method, this node ignores this input.

Default: 256

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histogram method

Method this node uses to compute the histogram. Currently, mode is the only available histogram method.

Name Description
mode Uses the mode method.
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reserved

Value reserved for future use.

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slope

The rate of change of the signal in a transition region between high reference level and low reference level.

This output can return a double-precision, floating-point number or a 1D array of double-precision, floating-point numbers.

The following equation defines slope:

slope = high reference level − low reference level transition duration
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transition duration

Time span, in seconds, of the transition.

This output can return a double-precision, floating-point number or a 1D array of double-precision, floating-point numbers.

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 figure:

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pre-transition: undershoot

Height of the local minimum preceding a rising or falling transition, which depends on the polarity you specify. Undershoot measures the height as a percentage of the histogram-based amplitude of the signal.

This output can return a double-precision, floating-point number or a 1D array of double-precision, floating-point numbers.

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pre-transition: overshoot

Height of the local maximum preceding a rising or falling transition, which depends on the polarity you specify. Overshoot measures the height as a percentage of the histogram-based amplitude of the signal.

This output can return a double-precision, floating-point number or a 1D array of double-precision, floating-point numbers.

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post-transition: undershoot

Height of the local minimum following a rising or falling transition, which depends on the polarity you specify. Undershoot measures the height as a percentage of the histogram-based amplitude of the signal.

This output can return a double-precision, floating-point number or a 1D array of double-precision, floating-point numbers.

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post-transition: overshoot

Height of the local maximum following a rising or falling transition, which depends on the polarity you specify. Overshoot measures the height as a percentage of the histogram-based amplitude of the signal.

This output can return a double-precision, floating-point number or a 1D array of double-precision, floating-point numbers.

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error out

Error information.

The node produces this output according to standard error behavior.

Standard Error Behavior

Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

error in does not contain an error error in contains an error
If no error occurred before the node runs, the node begins execution normally.

If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.
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measurement info

Transition interval end points and the absolute reference levels used to define the transition.

This output can return a cluster or a 1D array of clusters.

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start time

Time of the rising low reference level crossing or falling high reference level crossing that defines the start of the transition to be measured.

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end time

Time of the rising high reference level crossing or falling low reference level crossing that defines the end of the transition to be measured.

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ref levels

Three user-defined reference levels of the waveform in absolute units.

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high ref level

The high reference level.

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mid ref level

The middle reference level.

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low ref level

The low reference level.

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ref units

Units of the reference levels.

ref units is always absolute in measurement info.

How polarity Affects Undershoot and Overshoot

The following illustration shows the undershoot and overshoot when polarity is Rising.

The following illustration shows the undershoot and overshoot when polarity is Falling.

Algorithm for Calculating Pre-transition Outputs

This node calculates pre-transition: undershoot and pre-transition: overshoot according to the following table.

polarity pre-transition: undershoot pre-transition: overshoot
Rising 100 * ( low ⁢     state ⁢     ⁢ level ⁢ −   local ⁢     ⁢ minimum amplitude ) 100 * (   local ⁢     ⁢ maximum − low ⁢   state ⁢     level amplitude )
Falling 100 * ( high ⁢   state ⁢   level − local ⁢   minimum amplitude ) 100 * (   local ⁢     ⁢ maximum − high ⁢   state ⁢     level amplitude )

To calculate pre-transition: undershoot and pre-transition: overshoot, this node searches for a local minimum and local maximum in the pre-transition aberration region immediately preceding the beginning of the transition specified by edge number and polarity. 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). This node calculates the high state level, low state level, and amplitude from the input signal.

Algorithm for Calculating Post-transition Outputs

This node calculates post-transition: undershoot and post-transition: overshoot according to the following table.

polarity post-transition: undershoot post-transition: overshoot
Rising 100 * ( high ⁢     state ⁢     ⁢ level ⁢ −   local ⁢     ⁢ minimum amplitude ) 100 * (   local ⁢     ⁢ maximum − high ⁢   state ⁢     level amplitude )
Falling 100 * ( low ⁢     state ⁢     ⁢ level ⁢ −   local ⁢     ⁢ minimum amplitude ) 100 * (   local ⁢     ⁢ maximum − low ⁢   state ⁢     level amplitude )

To calculate post-transition: undershoot and post-transition: overshoot, this node searches for a local minimum and local maximum in the post-transition aberration region immediately following the end of the transition specified by edge number and polarity. 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). This node calculates the high state level, low state level, and amplitude from the input signal.

Where This Node Can Run:

Desktop OS: Windows

FPGA: DAQExpress does not support FPGA devices

Web Server: Not supported in VIs that run in a web application

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