Table Of Contents
Pulse Time and Transition Measurements (Transition) (G Dataflow)
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.
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
edge number
The transition to measure. An edge number of n with rising polarity selected indicates that the node measures the n th rising transition it detects in the input waveform.
reference levels settings
High and low reference levels required to determine the transition interval.
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
mid ref level
Middle reference level of the waveform.
mid ref level is not used in transition measurements.
Default: 50
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
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
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.
Default: No error
state levels settings
Settings that determine the high and low state levels of a waveform.
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
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
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. |
reserved
Value reserved for future use.
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:
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:
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.
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.
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.
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.
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.
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.
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.
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.
ref levels
Three user-defined reference levels of the waveform in absolute units.
high ref level
The high reference level.
mid ref level
The middle reference level.
low ref level
The low reference level.
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 | ||
| Falling |
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 | ||
| Falling |
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