Connecting Analog Voltage Signals to a DAQ Device

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NI Home > Support > Getting Started with NI Products > Connect and Set Up Hardware > Sensors for Data Acquisition > Connect Analog Voltage Signals
Getting Started with NI Products
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Install Software
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Connect Hardware
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Learn LabVIEW
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Begin Your Application
Install Software and Drivers
Connect and Set Up Hardware
Data Acquisition Devices
Sensors for Data Acquisition
Connecting Analog Voltage Signals to a DAQ Device
Included in the Section
Locating Your DAQ Device Pinout
Configuring an Analog Voltage Measurement
Connect Analog Voltage Signals
Connecting an Analog Voltage Signal to Your Device
Connect Analog Output Signals
Testing the Signal
Connect Current Signals
Connect Thermocouples
Connect Strain Gages
Connect Accelerometers
Connect Digital Input Signals
Connect Digital Output Signals
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Before You Begin
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This document provides step-by-step instructions for wiring and configuring your DAQ device for analog voltage measurements. Before
you begin using your DAQ hardware, you must install your application development environment and NI-DAQmx driver software. Refer to
the Installing LabVIEW and NI-DAQmx document for more information.
View an in-depth description
Locating Your DAQ Device Pinout
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Before connecting any signals, locate your device pinout.
1. Open Measurement & Automation Explorer (MAX) and expand Devices and Interfaces.
Connect Quadrature Encoders
2. Right-click on your device name, and then select "Device Pinouts."
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Figure 6. Device Terminals Help
The following terminal types correspond with analog voltage measurements:
1. AI X(+/-): Analog Input — This is usually followed by a number corresponding to a channel number. For instance, if your DAQ card
has 16 analog input channels, your pinout diagram probably shows positive and negative terminals for AI 0 through AI 15 located
throughout the connector. The + and – symbols refer to differential input channel pairs.
2. AI GND: Analog Ground — This terminal is electrically connected to the ground of the instrumentation amplifier on your DAQ
device.
3. AI SENSE — The AI SENSE terminal is a common reference point for certain single-ended input terminal configurations (NRSE and
RSE).
Configuring an Analog Voltage Measurement
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You can use MAX to quickly verify the accuracy of your measurement system Set Up. Using an NI-DAQmx Global Virtual Channel you
can configure a voltage measurement without any programming. A virtual channel is a concept of the NI-DAQmx driver architecture used
to represent a collection of device property settings that can include a name, a physical channel, input terminal connections, the type of
measurement or generation, and scaling information. Follow these steps to begin:
3. With MAX open, select Data Neighborhood and click Create New.
4. Select NI-DAQmx Global Virtual Channel and click Next.
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Connecting Analog Voltage Signals to a DAQ Device - National Instruments
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5. Select Acquire Signals » Analog Input » Voltage
Figure 7. Creating an NI-DAQmx Virtual Channel
6. Select the physical channel that you will connect your voltage measurement to. A physical channel is a terminal or pin at which you
can measure or generate an analog or digital signal. A single physical channel can include more than one terminal or pin, as in the
case of a differential input channel.
Figure 8. Device Physical Channels
7. Click Next and enter a name for the global virtual channel or leave the default.
8. Click Finish and you should see the following screen in MAX:
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Connecting Analog Voltage Signals to a DAQ Device - National Instruments
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Figure 9. Setting Up a Voltage Channel in MAX
9. On the settings tab, type in the minimum and maximum voltage values you expect to read from your measurement (-10 V to 10 V by
default). Doing this allows you to achieve more resolution in your measurement because the digital codes of the analog-to-digital
converter are spread evenly across the analog input range. So, if you expect and input a smaller range, the voltage input difference
between two consecutive codes is smaller.
10. Select your Terminal Configuration (Differential, RSE, NRSE, or Pseudodifferential) according to your wiring and the information
above.
Connecting an Analog Voltage Signal to Your Device
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The next step is to physically connect the voltage signal to your DAQ device.
11. Click the Connection Diagram tab in MAX to continue.
Figure 10. Analog Voltage Connection Diagram
The connection diagram above indicates which pins on your DAQ device should be wired according to the physical channel you selected.
In this example, a differential input connection uses pins 68 and 34, corresponding to ai0 (AI+) and ai8 (AI-). The diagram shows an SCC68 terminal block accessory. You can change this by right-clicking on the device name under Devices and Interfaces and selecting
Properties.
Testing the Signal
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With NI-DAQmx global virtual channels, you can preview your measurements.
12. With MAX still open, click back on the NI-DAQmx Global Channel tab and click on the Run button. The voltage value of your
measurement displayed at the top of the screen.
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Connecting Analog Voltage Signals to a DAQ Device - National Instruments
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Figure 11. Previewing a Voltage Measurement in MAX
You can choose to view the signal in tabular form or as a graph by selecting Graph from the Display Type pull-down menu. You also have
the option of saving your NI-DAQmx Global Virtual Channel should you want to refer to this configuration screen again in the future.
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