NI SCOPE Horizontal Attributes

Horizontal Attributes

• NISCOPE_ATTRIBUTE_MIN_SAMPLE_RATE
• NISCOPE_ATTRIBUTE_HORZ_MIN_NUM_PTS
• NISCOPE_ATTRIBUTE_HORZ_NUM_RECORDS
• NISCOPE_ATTRIBUTE_HORZ_RECORD_REF_POSITION
• NISCOPE_ATTRIBUTE_HORZ_SAMPLE_RATE
• NISCOPE_ATTRIBUTE_HORZ_RECORD_LENGTH
• NISCOPE_ATTRIBUTE_ENABLE_TIME_INTERLEAVED_SAMPLING
• NISCOPE_ATTRIBUTE_HORZ_ENFORCE_REALTIME
• NISCOPE_ATTRIBUTE_ALLOW_MORE_RECORDS_THAN_MEMORY
• NISCOPE_ATTRIBUTE_RIS_NUM_AVERAGES
• NISCOPE_ATTRIBUTE_RIS_METHOD
• NISCOPE_ATTRIBUTE_POLL_INTERVAL
• NISCOPE_ATTRIBUTE_REF_TRIG_TDC_ENABLE
• NISCOPE_ATTRIBUTE_HORZ_TIME_PER_RECORD
• NISCOPE_ATTRIBUTE_ACQUISITION_START_TIME

NISCOPE_ATTRIBUTE_MIN_SAMPLE_RATE

Specific Attribute

Data type	Access	Applies to	Coercion	High Level Functions
ViReal64	R/W	N/A	None	niScope_ConfigureHorizontalTiming

Description

Specifies the sampling rate (in Samples/second) for the acquisition. This attribute is invalid when the device is configured to use an external sample clock timebase. When a DDC is enabled, this attribute specifices the IQ rate. When both the NISCOPE_ATTRIBUTE_HORZ_TIME_PER_RECORD and NISCOPE_ATTRIBUTE_MIN_SAMPLE_RATE are set, the attribute that was set first is ignored.

Valid Values: The combination of sampling rate and minimum record length must allow the digitizer to sample at a valid sampling rate for the acquisition type specified in niScope_ConfigureAcquisition and not require more memory than the onboard memory module allows.

Related topics:

• Sample Rate
• Coercions of Horizontal Parameters

NISCOPE_ATTRIBUTE_HORZ_MIN_NUM_PTS

Specific Attribute

Data type	Access	Applies to	Coercion	High Level Functions
ViInt32	R/W	N/A	None	None

Description

Specifies the minimum number of points you require in the waveform record for each channel. NI-SCOPE uses the value you specify to configure the record length that the digitizer uses for waveform acquisition. NISCOPE_ATTRIBUTE_HORZ_RECORD_LENGTH returns the actual record length.

Valid Values: 1 – available onboard memory

Related topics:

• Coercions of Horizontal Parameters

NISCOPE_ATTRIBUTE_HORZ_NUM_RECORDS

Specific Attribute

Data type	Access	Applies to	Coercion	High Level Functions
ViInt32	R/W	N/A	None	None

Description

Specifies the number of records to acquire. Can be used for multirecord acquisitions and single record acquisitions. Setting this attribute to 1 indicates a single record acquisition.

Related topics:

• Making Multiple-Record Acquisitions

NISCOPE_ATTRIBUTE_HORZ_RECORD_REF_POSITION

Specific Attribute

Data type	Access	Applies to	Coercion	High Level Functions
ViReal64	R/W	N/A	None	None

Description

Specifies the position of the Reference Event in the waveform record. When the digitizer detects a trigger, it waits the length of time the NISCOPE_ATTRIBUTE_TRIGGER_DELAY_TIME attribute specifies. The event that occurs when the delay time elapses is the Reference Event. The Reference Event is relative to the start of the record and is a percentage of the record length. For example, the value 50.0 corresponds to the center of the waveform record and 0.0 corresponds to the first element in the waveform record.

Valid Values: 0.0 – 100.0

NISCOPE_ATTRIBUTE_HORZ_SAMPLE_RATE

Specific Attribute

Data type	Access	Applies to	Coercion	High Level Functions
ViReal64	RO	N/A	None	niScope_SampleRate

Description

Returns the effective sample rate using the current configuration. This attribute is only valid after a call to the one of the Configure Horizontal functions.

Units: hertz (Samples / Second)

Related topics:

• Sample Clock

NISCOPE_ATTRIBUTE_HORZ_RECORD_LENGTH

Specific Attribute

Data type	Access	Applies to	Coercion	High Level Functions
ViInt32	RO	N/A	None	niScope_ActualRecordLength

Description

Returns the actual number of points the digitizer acquires for each channel. The value is equal to or greater than the minimum number of points you specify with NISCOPE_ATTRIBUTE_HORZ_MIN_NUM_PTS.

Allocate a ViReal64 array of this size or greater to pass as the WaveformArray parameter of the Read and Fetch functions. This attribute is only valid after a call to the one of the Configure Horizontal functions. The value is equal to or greater than the minimum number of points you specify in niScope_ConfigureHorizontalTiming functions.

Related topics:

• Coercions of Horizontal Parameters

NISCOPE_ATTRIBUTE_ENABLE_TIME_INTERLEAVED_SAMPLING

Specific Attribute

Data type	Access	Applies to	Coercion	High Level Functions
ViBoolean	R/W	Channel	None	None

Description

Extends the maximum sample rate on the specified channel for devices that support Time Interleaved Sampling (TIS). TIS enables the device to use multiple ADCs to sample the same waveform at a higher effective real-time rate.

Default Value: VI_FALSE (0)

Defined Values

VI_TRUE (1)—Use multiple interleaved ADCs to acquire data for this channel.

VI_FALSE (0)—Use only this channel's ADC to acquire data for this channel.

Related topics:

• Time Interleaved Sampling
• Configuring the Horizontal Settings

NISCOPE_ATTRIBUTE_HORZ_ENFORCE_REALTIME

Specific Attribute

Data type	Access	Applies to	Coercion	High Level Functions
ViBoolean	R/W	N/A	None	None

Description

Indicates whether the digitizer enforces real-time measurements or allows equivalent-time measurements.

Defined Values

VI_TRUE

VI_FALSE

Related topics:

• Sampling Methods
• Real-Time Sampling
• Time Interleaved Sampling

NISCOPE_ATTRIBUTE_ALLOW_MORE_RECORDS_THAN_MEMORY

Specific Attribute

Data type	Access	Applies to	Coercion	High Level Functions
ViBoolean	R/W	N/A	None	niScope_ConfigureHorizontalTiming

Description

Indicates whether more records can be configured with niScope_ConfigureHorizontalTiming than fit in the onboard memory. If this attribute is set to VI_TRUE, it is necessary to fetch records while the acquisition is in progress. Eventually, some of the records are overwritten. An error is returned from the fetch function if you attempt to fetch a record that has been overwritten.

Defined Values

VI_TRUE (1)

VI_FALSE (0)

Related topics:

• Continuously Acquiring Data

NISCOPE_ATTRIBUTE_RIS_NUM_AVERAGES

Specific Attribute

Data type	Access	Applies to	Coercion	High Level Functions
ViInt32	R/W	N/A	None	None

Description

The number of averages for each bin in an RIS acquisition. The number of averages times the oversampling factor is the minimum number of real-time acquisitions necessary to reconstruct the RIS waveform. Averaging is useful in RIS because the trigger times are not evenly spaced, so adjacent points in the reconstructed waveform cannot be accurately spaced. By averaging, the errors in both time and voltage are smoothed.

Related topics:

• Equivalent-Time Sampling and Random Interleaved Sampling

NISCOPE_ATTRIBUTE_RIS_METHOD

Specific Attribute

Data type	Access	Applies to	Coercion	High Level Functions
ViInt32	R/W	N/A	None	None

Description

Specifies the algorithm for random-interleaved sampling, which is used if the sample rate exceeds the value of NISCOPE_ATTRIBUTE_MAX_REAL_TIME_SAMPLING_RATE.

Defined Values

NISCOPE_VAL_RIS_EXACT_NUM_AVERAGES	(1)	Acquires exactly the specified number of records for each bin in the RIS acquisition. An error is returned from the fetch function if the RIS acquisition does not successfully acquire the specified number of waveforms within the timeout period. You may call the fetch function again to allow more time for the acquisition to finish.
NISCOPE_VAL_RIS_MIN_NUM_AVERAGES	(2)	Each RIS sample is the average of at least Min Num Avg randomly distributed points. Any extra points taken are also averaged in.
NISCOPE_VAL_RIS_INCOMPLETE	(3)	Returns the RIS waveform after the specified timeout even if it is incomplete. If no waveforms have been acquired in certain bins, these bins have an NaN (when fetching scaled data) or a zero (when fetching binary data). A warning (positive error code) is returned from the fetch function if the RIS acquisition did not finish. The acquisition aborts when data is returned.
NISCOPE_VAL_RIS_LIMITED_BIN_WIDTH	(5)	Limits the waveforms in the various bins to be within 200 ps of the center of the bin.

Related topics:

• Equivalent-Time Sampling and Random Interleaved Sampling
• Configuring the Horizontal Settings

NISCOPE_ATTRIBUTE_POLL_INTERVAL

Specific Attribute

Data type	Access	Applies to	Coercion	High Level Functions
ViInt32	R/W	N/A	None	None

Description

Specifies the poll interval in milliseconds to use during RIS acquisitions to check whether the acquisition is complete.

NISCOPE_ATTRIBUTE_REF_TRIG_TDC_ENABLE

Specific Attribute

Data type	Access	Applies to	Coercion	High Level Functions
ViBoolean	R/W	N/A	None	None

Description

This attribute controls whether the TDC is used to compute an accurate trigger.

Defined Values

VI_TRUE

VI_FALSE

Related topics:

• TDC

NISCOPE_ATTRIBUTE_HORZ_TIME_PER_RECORD

Specific Attribute

Data type	Access	Applies to	Coercion	High Level Functions
ViReal64	R/W	N/A	None	None

Description

Specifies the length of time (in seconds) that corresponds to the record length. This attribute is invalid when the device is configured to use an external sample clock timebase. This attribute is also invalid when a DDC is enabled. When both NISCOPE_ATTRIBUTE_HORZ_TIME_PER_RECORD and NISCOPE_ATTRIBUTE_MIN_SAMPLE_RATE are set, the attribute that was set first is ignored.

Units: Seconds

Related topics:

• Coercions of Horizontal Parameters

NISCOPE_ATTRIBUTE_ACQUISITION_START_TIME

Specific Attribute

Data type	Access	Applies to	Coercion	High Level Functions
ViReal64	R/W	N/A	None	None

Description

Specifies the length of time from the trigger event to the first point in the waveform record in seconds. If the value is positive, the first point in the waveform record occurs after the trigger event (same as specifying NISCOPE_ATTRIBUTE_TRIGGER_DELAY_TIME. If the value is negative, the first point in the waveform record occurs before the trigger event (same as specifying NISCOPE_ATTRIBUTE_HORZ_RECORD_REF_POSITION.