Arbitrary Waveform Overview

The IviFgenArbWfm Extension Group supports function generators capable of producing user-defined arbitrary waveforms. You can modify parameters of the arbitrary waveform such as sample rate, waveform gain, and waveform offset. The IviFgenArbWfm extension group includes VIs for creating, configuring, and generating arbitrary waveforms, and for returning information about arbitrary waveform creation.

This extension affects instrument behavior when the IviFgen Output Mode property is set to IVIFGEN_VAL_OUTPUT_ARB or IVIFGEN_VAL_OUTPUT_SEQ .

Before a function generator can produce an arbitrary waveform, you must configure some signal generation properties. This specification provides definitions for arbitrary waveform properties that must be followed when developing instrument drivers. The definition of an arbitrary waveform and its properties are given in the following list:

• Arbitrary Waveform—A user-defined series of sequential data points, between -1.0 and 1.0 inclusive, that describe an output waveform.
• Gain—The factor by which the function generator scales the arbitrary waveform data. For example, a gain value of 2.0 causes the waveform data to range from -2.0 V to +2.0 V.
• Offset—The value the function generator adds to the scaled arbitrary waveform data. For example, scaled arbitrary waveform data that ranges from -1.0 V to +1.0 V is generated from 0.0 V to 2.0 V when the end user specifies a waveform offset of 1.0 V.

Note  The offset is added to any inherent offset in the arbitrary waveform data.

The following figures illustrate the definitions for arbitrary waveform properties.

Examples of Normalized, Scaled, and Offset Data

Size, Sample Rate, and Time Elements of a Waveform

The sample rate is the reciprocal of the amount of time for which points in the arbitrary waveform is generated. The frequency at which the function generator produces one cycle of an arbitrary waveform can be expressed by the equation: