Virtual channel


Course contents


Labview basics

– virtual instruments, data flow, palettes



– for, while, case, ...

– editing techniques



– arrays, clusters, charts, graphs


Additional lecture

– State machines, SubVIs, MainCluster


Modular programming + recording

– SubVIs

– File I/O

– Analysis

– Signal processing

– Communication between loops


Instrument control

– DAQ , Data collection, GPIB, Serial


Additional lecture

– Data Acquisition, Instrument control

Measurement & Automation Explorer


• View and control your devices and software

Create simulated device

• You can test your code without the hardware

Create simulated device

• Real devices are green

• Simulated devices are yellow

– simulated devices work just like real devices

Test panel

• Check pinouts


• Self Test


DAQ Assistant

• Create new task

– put express VI to block diagram

DAQ Assistant

DAQ Assistant

DAQ Assistant

• Define Task

– 1 sample

Acquire 1 sample with DAQ assistant

Acquire multiple samples from multiple channels

Acquire multiple samples from multiple channels

• N Samples

Acquire multiple samples from multiple channels

• You can sample within a loop

Acquire continuosly

Acquire continuosly

Create NI-DAQmx tasks from MAX

Define Task

Define Task

• Tasks are visible in all LabVIEW applications

• Input range

• Timing

• Terminal configuration

• Add channels

Task settings

Run task

• Simulated device will produce sine wave

• Press Save to save the task settings

Test simulated device on LabVIEW

• Hardware Input and Output»DAQmx»Analog

Measurements»Voltage»Cont Acq&Graph Voltage-Int Clk.VI

Test simulated device on LabVIEW

Create task from express VI

Generate code from express VI

• Express VI set to Continuos mode

Generate code from Task name constant

Generate code from Task name constant

Output voltages

• N samples

• Generate >> Example

Output Voltages

• 1 Sample

Digital input

• 1 Sample

• Generate >> Example

Digital input

• 1 Sample

Digital output

Triggered acquisition


NI DAQmx Help

• Start»Programs»National Instruments»NI-DAQ


Physical channel - A terminal or pin at which you can measure or generate an analog or digital signal.

Virtual channel - A collection of settings that can include a name, a physical channel, input terminal connections, the type of measurement or generation, and scaling information. In NI-DAQmx, virtual channels are integral to every measurement. You can configure virtual channels with the DAQ Assistant, which you can open from

Measurement & Automation Explorer (MAX) or your application software. You also can configure virtual channels with the NI-DAQmx API in your application program.

Task - A collection of one or more virtual channels with timing, triggering, and other properties. Conceptually, a task represents a measurement or generation you want to perform. You can set up and save all of the configuration information in a task and use the task in an application. In NI-DAQmx, you can configure virtual channels as part of a task or separate from a task.

Local channels - Virtual channels created inside a task.

Global channels - Virtual channels defined outside a task. You can create global channels in MAX or in your application software. You can use global channels in any application or add them to a number of different tasks. If you modify a global channel, the change affects all tasks in which you reference that global channel. In most cases, it is simpler to use local channels.


• DAQmx Simulated Devices


• DAQ Assistant and automatic code generation


• Useful DAQmx functions


• Continuous vs. Finite Sampling



• Read multiple channels sequentially (advanced)