IVI Scope Acquire Express VI

LabView Acquire Signals Express VIs

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IVI Scope Acquire Express VI

Owning Palette: Acquire Signals Express VIs

Installed With: LabVIEW SignalExpress

Acquires an analog waveform from an instrument in the Oscilloscope IVI Class.

Default values are specific to the hardware and driver specified. The default settings might not be applicable to the measurement you are trying to perform.

The IVI Scope Acquire toolbar includes two buttons you can use to set parameter values. Click the Initialize button to set IVI Scope Acquire to the default settings. Click the Autosetup button to set parameters to values that IVI Scope Acquire determines best fit the signal you are acquiring.

Note Clicking the Autosetup button executes IVI Scope Acquire.

To communicate with an instrument, you need to install the instrument-specific driver and create a session name for the instrument.

Dialog Box Options

Place on the block diagram

Find on the Functions palette

Dialog Box Options

Parameter

Description

Autoscale amplitude

Scales the amplitude axis of the Acquired signals graph. The default is to autoscale the amplitude.

Acquired Signals

Displays the waveform from the device. Range (V) and Offset (V) set the hardware limits.

Configuration

Contains the following configuration options:

Device—Contains the following device options:
- IVI session name—Specifies the session name to use for this step. This step retrieves possible session names from National Instruments Measurement & Automation Explorer (MAX). You also can create a new session or edit/delete an existing session.
- Resource descriptor—Specifies the interface and the address of the hardware to associate with the step.
- Instrument driver—Displays the name of the driver in use.
Vertical—Contains channel configuration options that affect the data along the Voltage (V) axis. The settings you configure with these options are specific to the channel you select in the Channels field. Vertical contains the following options:
- Channels—Specifies the physical channels from which to generate data.
- Enable channel—Specifies whether to enable data acquisition on the selected channel.
- Range (V)—Specifies the value of the input range the oscilloscope uses for the channel. For example, to acquire a sine wave that spans -5 to 5 volts, enter 10 as the value of this parameter.
- Input impedance (Ohms)—Specifies the input impedance you want to use for the channel.
- Probe attenuation—Specifies the scaling factor by which the probe you attach to the channel attenuates the input. Pass -1 to auto detect.
- Offset (V)—Specifies the location of the center of the range that you specify with Range (V). Enter the value with respect to ground. For example, to acquire a sine wave that spans 0 to 10 volts, enter 5 as the value of this parameter.
- Coupling—Specifies how you want the oscilloscope to couple the input signal for the channel. Options include AC, DC, and GND.
- Bandwidth (Hz)—Specifies the maximum frequency for the input signal you want the instrument to accommodate without attenuating the signal by more than 3 dB.
Horizontal—Contains the following device-specific options for configuring the Time (s) axis:
- Start time (s)—Specifies the length of time from the trigger event to the first point in the waveform record. If this value is positive, the first point in the waveform record occurs after the trigger event. If this value is negative, the first point in the waveform record occurs before the trigger event.
- Time per record (s)—Specifies the time in seconds that corresponds to the record length.
- Min record length (S)—Specifies the minimum number of points you require in the waveform record for each channel.

Trigger

Contains the following trigger options:

Type—Specifies the type of trigger you want the oscilloscope to use. Contains the following options:
- Immediate— Configures the oscilloscope for immediate triggering. The oscilloscope does not wait for a trigger of any kind upon initialization.
- Edge—Configures the oscilloscope for edge triggering. An edge trigger occurs when the trigger signal crosses the trigger level you specify with the slope you specify.
- TV—Configures the oscilloscope for TV triggering.
- Runt—Configures the oscilloscope for runt triggering. A runt trigger occurs when the trigger signal crosses one of the runt thresholds twice without crossing the other runt threshold.
- Glitch—Configures the oscilloscope for glitch triggering. A glitch trigger occurs when the trigger signal has a pulse with a width that is less than the glitch width. The trigger does not actually occur until the edge of the pulse that corresponds to the glitch width and polarity you specify crosses the trigger level.
- Width—Configures the oscilloscope for width triggering. A width trigger occurs when the oscilloscope detects a positive or negative pulse with a width between, or optionally outside, the width thresholds. The trigger does not actually occur until the edge of a pulse that corresponds to the width thresholds and polarity you specify crosses the trigger level.
- AC Line—Configures the oscilloscope for AC line triggering.
Source—Specifies the source for the oscilloscope to monitor for a trigger.
Holdoff (s)—Specifies the length of time you want the oscilloscope to wait after it detects a trigger until the oscilloscope enables the trigger subsystem to detect another trigger.
Timeout (s)—Specifies the maximum amount of time to wait for the oscilloscope to acquire data. When a timeout occurs during an acquisition, it is normally due to a failure to trigger. The default is 10.

Level (V)—[Type: Edge] Specifies the voltage you want the oscilloscope to use for edge triggering. The oscilloscope triggers when the trigger signal passes through the threshold you specify with this parameter and has the slope you specify with the Slope parameter.

Note This parameter affects instrument behavior only when you select a channel or the external trigger input as the trigger source. You may not configure the trigger level that the oscilloscope uses for other trigger sources, such as VXI TTL trigger lines.

Slope—[Type: Edge] Specifies whether you want a rising edge or a falling edge passing through the trigger level to trigger the oscilloscope. Options include Positive and Negative.
Coupling—[Type: Edge] Specifies the trigger coupling. Options include AC, DC, HF Reject, LF Reject, and Noise Reject.
Polarity—[Type: TV] Specifies the polarity of the TV signal. Options include Positive and Negative.
Signal format—[Type: TV] Specifies the type of TV signal on which the oscilloscope triggers. Options include NTSC, PAL, and SECAM.
Event—[Type: TV] Specifies the TV event on which you want the oscilloscope to trigger. Options include Field 1, Field 2, Any Field, Any Line, and Line Number.
Line number—[Type: TV] Specifies the line in the field on which you want the oscilloscope to trigger. The specified line number is independent of any field. This means that to trigger on the first line of Field 2, you must specify a line number of 263 (if we assume that Field 1 has 262 lines).
Polarity—[Type: Runt] Specifies the polarity of the runt that you want to trigger the oscilloscope. Contains the following options:
- Positive—Triggers on a positive runt. A positive runt occurs when a rising edge crosses the Low threshold (V) and does not cross the High threshold (V) before recrossing the Low threshold (V).
- Negative—Triggers on a negative runt. A negative runt occurs when a falling edge crosses the High threshold (V) and does not cross the Low threshold (V) before recrossing the High threshold (V).
- Either—Triggers on either a positive or negative runt.
Low threshold (V)—[Type: Runt] Specifies the low threshold you want the oscilloscope to use for runt triggering.
High threshold (V)—[Type: Runt] Specifies the high threshold you want the oscilloscope to use for runt triggering.
Level (V)—[Type: Glitch] Specifies the voltage threshold you want the oscilloscope to use for glitch triggering. The oscilloscope triggers when a glitch crosses the trigger threshold you specify with this parameter.
Polarity—[Type: Glitch] Specifies the polarity of the glitch that you want to trigger the oscilloscope. Options include Positive, Negative, and Either.
Condition—[Type: Glitch] Specifies the glitch condition. The oscilloscope triggers when it detects a pulse with a width less than or greater than the Width (s) value. Options include Less Than and Greater Than.
Width (s)—[Type: Glitch] Specifies the length of time you want the oscilloscope to use for the glitch width. The oscilloscope triggers when it detects a pulse with a width less than or greater than this value, depending on the Condition parameter.
Level (V)—[Type: Width] Specifies the voltage threshold you want the oscilloscope to use for width triggering. The oscilloscope triggers when the edge of a pulse that corresponds to the Low threshold (V), High threshold (V), Condition, and Polarity crosses the threshold you specify in this parameter.
Polarity—[Type: Width] Specifies the polarity of the pulse that you want to trigger the oscilloscope. Options include Positive and Negative.
High threshold (V)—[Type: Width] Specifies the high width threshold.
Low threshold (V)—[Type: Width] Specifies the low width threshold.
Condition—[Type: Width] Specifies whether you want a pulse that is within or outside the High threshold (V) and Low threshold (V) to trigger the oscilloscope. Contains the following options:
- Within—Triggers on pulses that have a width that is less than the High threshold (V) and greater than the Low Threshold (V).
- Outside—Triggers on pulses that have a width that is either greater than the High threshold (V) or less than the Low threshold (V).
Slope—[Type: AC Line] Specifies whether you want the oscilloscope to trigger on a zero crossing with a positive, negative, or either slope of the network supply voltage. Options include Positive, Negative, and Either.

Advanced

Contains the following option:

Acquisition Settings—Contains the following option:
- Acquisition type—Specifies the manner in which you want the oscilloscope to acquire data and fill the waveform record. Contains the following options:
  - Normal—Sets the oscilloscope to normal acquisition mode. The oscilloscope acquires one sample for each point in the waveform record. The oscilloscope can use real-time or equivalent-time sampling.
  - Peak Detect—Sets the oscilloscope to the peak-detect acquisition mode. The oscilloscope oversamples the input signal and keeps the minimum and maximum values that correspond to each position in the waveform record. The oscilloscope uses only real-time sampling.
  - High Resolution—Sets the oscilloscope to the high-resolution acquisition mode. The oscilloscope oversamples the input signal and calculates an average value for each position in the waveform record. The oscilloscope uses only real-time sampling.
  - Envelope—Sets the oscilloscope to the envelope acquisition mode. The oscilloscope acquires multiple waveforms and keeps the minimum and maximum voltages it acquires for each point in the waveform record. The oscilloscope can use real-time or equivalent-time sampling.
  - Average—Sets the oscilloscope to the average acquisition mode. The oscilloscope acquires multiple waveforms and calculates an average value for each point in the waveform record. The oscilloscope can use real-time or equivalent-time sampling.
  Note When you set this parameter to Envelope or Peak Detect, the oscilloscope acquires minimum and maximum waveforms.

Execution Control

Contains the following execution control options:

Start this step after—Makes the step wait until another step has started before executing. You can make the step wait on any other hardware step in the project by selecting the step to wait on from the pull-down menu.

You can use this option to force an acquisition device to start after a generation device starts. You also can use this option to ensure that a device generating a trigger signal starts after the device receiving the signal, which avoids sending the signal before the receiver is ready.
Step to wait for—Lists the possible steps for which this step can wait.
Pre-execution delay (ms)—Specifies the amount of time to wait before the step executes. If you configure the step to start after another step, the delay represents the amount of time to wait after the specified step starts.
Post-execution delay (ms)—Specifies the amount of time to wait after the step executes.

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