Table Of Contents

Internal Channels for DSA Devices

Last Modified: November 16, 2017

On a DSA device, you can either acquire a signal present on the I/O connector, or you can acquire a signal that is generated from the internal calibration multiplexer. The channels available on this multiplexer are typically used for calibration purposes, but you can also sample them as you would a physical signal present on the I/O connector. To read from one of these internal channels, you must use one of the device's AI physical channels (for instance, Dev1/ai0) when creating the channel to select which ADC to use, then set the appropriate string value on the Input Source channel attribute/property.

The following table lists internal channels for DSA devices.

Internal Channel Name Supported Devices Description
_external_channel All DSA devices The source of the AI channel is the device input connector, or an accessory connected to the device connector.
_5Vref_vs_aignd 4461/4462/4464, 447x The source of the AI channel is the onboard reference signal (for example, +5V).
_pos10V_vs_aignd 4464 The source of the AI channel is the onboard reference signal (for example, +10V).
_neg10V_vs_aignd 4464 The source of the AI channel is the onboard reference signal (for example, -10V).
_pos1V_vs_aignd 4464 The source of the AI channel is the onboard reference signal (for example, +1V).
_pos316mV_vs_aignd 4464 The source of the AI channel is the onboard reference signal (for example, +316mV).
_aignd_vs_pos10V 4464 The source of the AI channel is the onboard reference signal (for example, +10V). The negative terminal is connected to the ground reference for analog input.
_aignd_vs_neg10V 4464 The source of the AI channel is the onboard reference signal (for example, -10V). The negative terminal is connected to the ground reference for analog input.
_ao0_vs_ao0neg[1] 4461 only The source of the AI channel is the onboard analog output channel 0.
_ao1_vs_ao1neg[1] 4461 only The source of the AI channel is the onboard analog output channel 1.
_aignd_vs_aignd 4461/4462/4464, 447x, 449x The source of the AI channel is the onboard ground signal.
_ref_sqwv_vs_aignd 449x The source of the AI channel is the onboard reference square wave signal.

For all DSA devices, only one internal channel can be read at a time, although the same internal channel can be read on multiple physical channels (with additional restrictions for NI 447x devices). For example, you cannot simultaneously read the internal 5 V reference on one physical channel and the analog ground on another physical channel.

The NI 447x AI physical channels are grouped into pairs, for instance {ai0, ai1}, {ai2, ai3}, and so on. NI 447x devices cannot read an internal channel on more than one physical channel group, and when reading an internal channel, both physical channels in the group are connected to the internal channel source. For example, if the Input Source for channel ai0 is set to 5Vref_vs_aignd and the Input Source for channel ai1 is left at the default value of _external_channel, ai1 still reads the internal channel 5Vref_vs_aignd since ai0 and ai1 are in the same physical channel group.

  • 1 The AO internal channels are valid only for devices with AO physical channels.

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