Networking Two PCs for Remote Data Acquisition

Overview

NI-DAQ for Windows version 6.0 or later, which comes free of charge with all National Instruments data acquisition (DAQ) products, includes a feature called Remote Device Access (RDA). With RDA, you can acquire data over a network using a National Instruments DAQ device installed in a remote computer. This type of acquisition is useful in situations with long assembly lines or huge test systems that require a single operator to acquire data from many different environments.

The underlying network protocol used by RDA is TCP/IP, so you can use the Internet or a dual-computer connection using TCP/IP as the communication layer to transfer data from the remote computer to the client. Moreover, RDA can be used on any existing local area network (LAN) or wide area network (WAN) that uses TCP/IP as the communications protocol. In these situations, you should consult your network administrator to properly install all computers on your network.

RDA works with LabVIEW, LabWindows/CVI Easy I/O, and VI Logger under Windows XP, Windows 2000, Windows NT, and Windows 9.x. Currently this feature is not available for third-party compilers, such as Visual C or Visual Basic, or for Mac OS. Click here for more information on remote data acquisition for Macintosh computers.

Using popular operating systems, this application note will explain how to accomplish remote data acquisition using network communication between the remote and client computers.

The following figure illustrates the typical system configuration for remote data acquisition.

General Requirements

The following are general requirements for implementing a 2-station Ethernet LAN-based RDA setup:

• PC with NI-DAQ 6.9.x (or earlier) for Windows installed, functioning as the RDA Server. This machine should also have an installed DAQ device.
• PC with NI-DAQ 6.9.x (or earlier) for Windows installed, functioning as the RDA Client. This machine should also have LabVIEW, LabWindows/CVI, or other application software.
• Properly configured network connections on both computers, both in hardware and software. Consult your network administrator to complete this point.
• Optional: signal conditioning accessory to condition the signal to be read; for further information, visit NI's Signal Conditioning Website.

You can also network both computers to perform remote data acquisition through a hub or by using a crossover Ethernet cable. However, these two methods are beyond the scope of this application note, as it focuses only on the Internet connection because it is the most widely used. Your network administrator can help you configure your computers in either of these ways.

Installing and Configuring the System

Windows XP

RDA Server Installation & Configuration

• Install NI-DAQ 6.9.x or earlier on the computer. Also install and configure the DAQ device and then the signal conditioning accessory, if you have one. For more details on installing and configuring National Instruments DAQ devices and signal conditioning accessories, visit the following link: ni.com/support/daq This Web site provides instructions to set up the device hardware and software.
• Determine the IP address of the server machine: Go to Start >> Run and type command, then press <Enter>. In the DOS window that appears, type ipconfig and press <Enter>. The IP address should appear listed in the window, along with some other network data. This DOS window is illustrated in the following figure.

[+] Enlarge Image

• Go to Start>>Program>>National Instruments>>NI-DAQ and select Remote Device Access Server to launch the server. If you want this computer to become an RDA Server every time it starts up, place a shortcut to the Remote Device Access Server in your Startup folder.

RDA Client Installation and Configuration

• Install LabVIEW 6.1 or another application development environment.
• If you chose not to install NI-DAQ in the previous step, install it now. Be sure that the same version of NI-DAQ is on both computers. If not, you might encounter the "Cannot Connect to Remote Server" error. For more information on this error, refer to the following KnowledgeBase entries: KB 1W4A4RUE and KB 1GTBAHW3.
• Check the TCP/IP connection between the two computers. To perform this check, go to Start >> Run and type ping and the IP address you obtained in Step 2 of the Server Installation and Configuration instructions. If you receive several lines of text that read "Reply from xxx.xxx.xxx.xxx bytes=..." then the network communication is working properly. Refer to the following figure for an illustration of this response.

Note: If this step fails, check with your network administrator. The remote device may be behind a firewall, so you will need to ask the network administrator how to access it.

• Launch Measurement & Automation Explorer (MAX). Right-click on Devices and Interfaces and choose Create New, then RDA/Ethernet Device, then click Finish. Next, in the dialog box that appears, type the IP address of the server computer, choose the device you want, and finally select a device number that is not currently used in this computer. The remote device should now appear listed under Devices and Interfaces in MAX. If you chose to install an SCXI system in the server, this will not appear in the client PC Devices and Interfaces list when you connect to the RDA Server.

• Test the resources of this new device to ensure it is working properly. If it passes the test, then the RDA setup is correct. To perform this operation, right-click the new device icon under Devices and Interfaces, and in the Configuration window, click the Modify Configuration... button. Refer to the following figure for an illustration of this step.

Windows 2000

RDA Server Installation and Configuration

• Install NI-DAQ on the computer. Also, install and configure the DAQ device and the signal conditioning accessory, if you have one. For more details on how to install and configure National Instruments DAQ devices and signal conditioning accessories, refer to ni.com/support/daq. There, you will find instructions to set up the device hardware and software.
• Determine the IP address of the server machine: Go to Start >> Run and type command, then press <Enter>. In the DOS window that appears, type ipconfig and press <Enter>. The IP address should appear listed in the window, along with some other network data. This DOS window is illustrated in the following figure.

[+] Enlarge Image

• Go to Start>>Program>>National Instruments>>NI-DAQ and select Remote Device Access Server to launch the server. If you want this computer to become an RDA Server every time it starts up, place a shortcut to the Remote Device Access Server in your Startup folder.

RDA Client Installation and Configuration

• Install LabVIEW 6.1 or another application development environment.
• If you chose not to install NI-DAQ in the previous step, install it now. Be sure that the same version of NI-DAQ is on both computers. If not, you might encounter the "Cannot Connect to Remote Server" error. For more information on this error, refer to the following KnowledgeBase entries: KB 1W4A4RUE and KB 1GTBAHW3.
• Check the TCP/IP connection between the two computers. To perform this check, go to Start >> Run and type ping and the IP address you obtained in Step 2 of the Server Installation and Configuration instructions. If you receive several lines of text that read "Reply from xxx.xxx.xxx.xxx bytes=..." then the network communication is working properly. Refer to the following figure for an illustration of this response.

• Note: If this step fails, check with your network administrator. The remote device may be behind a firewall, so you will need to ask the network administrator how to access it.
• Launch Measurement & Automation Explorer (MAX). Right-click on Devices and Interfaces and choose Create New, then RDA/Ethernet Device, then click Finish. Next, in the dialog box that appears, type the IP address of the server computer, choose the device you want, and finally select a device number that is not currently used in this computer. The remote device should now appear listed under Devices and Interfaces in MAX. If you chose to install an SCXI system in the server, this will not appear in the client PC Devices and Interfaces list when you connect to the RDA Server.
  
  
  
  
• Test the resources of this new device to ensure it is working properly. If it passes the test, then the RDA setup is correct. To perform this operation, right-click the new device icon under Devices and Interfaces, and in the Configuration window, click the Modify Configuration... button. Refer to the following figure for an illustration of this step.

Windows NT

RDA Server Installation and Configuration

• Install NI-DAQ 6.9.2 on the computer. Also, install and configure the DAQ device and the signal conditioning accessory, if you have one. For more information on installing and configuring National Instruments DAQ devices and signal conditioning accessories, refer to ni.com/support/daq. There you will find instructions on setting up the device hardware and software.
• Determine the IP address of the server machine: Go to Start>>Run, type ipconfig and press <Enter>. The IP address should appear listed in the window, along with some other network data. This DOS window is illustrated in the following figure.

• Go to Start>>Program>>National Instruments>>NI-DAQ and select Remote Device Access Server to launch the server. If you want this computer to become an RDA Server every time it starts up, place a shortcut to the Remote Device Access Server in your Startup folder.

RDA Client Installation and Configuration

• Install LabVIEW 6.1 or another application development environment.
• If you chose not to install NI-DAQ in the previous step, install it now. Be sure that the same version of NI-DAQ is on both computers. If not, you might encounter the "Cannot Connect to Remote Server" error. For more information on this error, refer to the following KnowledgeBase entries: KB 1W4A4RUE and KB 1GTBAHW3.
• Check the TCP/IP connection between the two computers. To perform this check, go to Start >> Run and type ping and the IP address you obtained in Step 2 of the Server Installation and Configuration instructions. If you receive several lines of text that read "Reply from xxx.xxx.xxx.xxx bytes=..." then the network communication is working properly. Refer to the following figure for an illustration of this response.

• Note: If this step fails, check with your network administrator. The remote device may be behind a firewall, so you will need to ask the network administrator how to access it.
• Launch Measurement & Automation Explorer (MAX). Right-click on Devices and Interfaces and choose Create New, then RDA/Ethernet Device, then click Finish. Next, in the dialog box that appears, type the IP address of the server computer, choose the device you want, and finally select a device number that is not currently used in this computer. The remote device should now appear listed under Devices and Interfaces in MAX. If you chose to install an SCXI system in the server, this will not appear in the client PC Devices and Interfaces list when you connect to the RDA Server.
  
  
  
  
• Test the resources of this new device to ensure it is working properly. If it passes the test, then the RDA setup is correct. To perform this operation, right-click the new device icon under Devices and Interfaces, and in the Configuration window, click the Modify Configuration... button. Refer to the following figure for an illustration of this step.

Windows 9x

RDA Server Installation and Configuration

• Install NI-DAQ 6.9.2 on the computer. Also, install and configure the DAQ device and the signal conditioning accessory, if you have one. For more information on installing and configuring National Instruments DAQ devices and signal conditioning accessories, refer to ni.com/support/daq. There you will find instructions on setting up the device hardware and software.
• Determine the IP address of the server machine: Go to Start>>Run, type winipcfg and press <Enter>. The IP address and some other network data should appear in a window. Refer to the following figure for an illustration of this window.
  
  
  
  
• Go to Start>>Programs>>National Instruments>>NI-DAQ and select Remote Device Access Server to launch the server.

RDA Client Installation and Configuration

• Install LabVIEW 6.1 or another application development environment.
• If you chose not to install NI-DAQ in the previous step, install it now. Be sure that the same version of NI-DAQ is on both computers. If not, you might encounter the "Cannot Connect to Remote Server" error. For more information on this error, refer to the following KnowledgeBase entries: KB 1W4A4RUE and KB 1GTBAHW3.
• Check the TCP/IP connection between the two computers. To perform this check, go to Start >> Run and type ping and the IP address you obtained in Step 2 of the Server Installation and Configuration instructions. If you receive several lines of text that read "Reply from xxx.xxx.xxx.xxx bytes=..." then the network communication is working properly. Refer to the following figure for an illustration of this response.

• Note: If this step fails, check with your network administrator. The remote device may be behind a firewall, so you will need to ask the network administrator how to access it.
• Launch Measurement & Automation Explorer (MAX). Right-click on Devices and Interfaces and choose Create New, then RDA/Ethernet Device, then click Finish. Next, in the dialog box that appears, type the IP address of the server computer, choose the device you want, and finally select a device number that is not currently used in this computer. The remote device should now appear listed under Devices and Interfaces in MAX. If you chose to install an SCXI system in the server, this will not appear in the client PC Devices and Interfaces list when you connect to the RDA Server.
  
  
  
  
• Test the resources of this new device to ensure it is working properly. If it passes the test, then the RDA setup is correct. To perform this operation, right-click the new device icon under Devices and Interfaces, and in the Configuration window, click the Modify Configuration... button. Refer to the following figure for an illustration of this step.

RDA Installation Considerations

1. A computer can be both a RDA Server and a RDA Client at the same time. Furthermore, servers and clients can run a mix of Windows versions – 9x, NT, 2000, or XP.
2. The NI-DAQ version for both the RDA Server and the RDA Client must match. If not, the network connection and transfer cannot occur.
3. You can power on and off the RDA Clients without affecting the state of the RDA Servers to which the client has assigned local device numbers. Also, you can load and unload the Remote Device Access Server, but you must refresh MAX and click the Test Resources button to reconnect the remote device from the RDA Client to the RDA Server.
4. If you assign a local device number to a remote device, NI-DAQ attempts to connect to the RDA Server each time it loads in the RDA Client. If the RDA Server is powered off, the RDA Client appears to stall during this process. This stalling is the timing out of the attempt to connect to the server computer. When the connection fails, any attempt to use the remote device will result in a -10340 (noConnectError) status error code, and you must repeat the configuration process.
5. RDA Client programs should perform all clean-up activities on the remote device. Failure to do so can result in lost resources on the RDA Server and can cause unpredictable behavior.
6. To access an SCXI module from a client PC through the RDA Server, you must use the device number that represents the RDA Device in MAX and use the channel given in the SCXI address form. This form is "ob0!scx!mdy!z," where x is this SCXI chassis number, y is the SCXI module number, and z is the channel number that you want to access on the SCXI module.
7. Virtual channels can be used to address remote National Instruments DAQ device channels as well as remote SCXI module channels. Moreover, these items can be installed at either the remote computer or the client computer. At the remote computer, they must be installed before the RDA configuration takes place. However, at the client computer, they must be set up after the RDA configuration. Furthermore, as already stated, the remote SCXI chassis and modules will not be listed under Devices and Interfaces in MAX on the client computer, yet when configuring virtual channels addressing remote SCXI modules, they will be listed in order to be addressed in the configuration wizard from the client computer. The following two figures show the difference between how the virtual channels are presented in MAX and LabVIEW.

The following benchmark tests were performed to demonstrate the RDA feature provided by NI-DAQ 6.9.2 under LabVIEW 6.1. For performing these tests, the following hardware was used:

• Demo server: 1 Dell GX150, 1 PCI-MIO-16E-4
• Demo client: 1 Dell GX150, 1 PCI-MIO-16E-4

The results from these benchmark tests may vary depending upon the computer and the DAQ devices used, the number of applications running during the acquisition on both the remote and client computers, and the data processing performed by each application.

Benchmark Tests

Benchmark Test 1
Use Cont Acq&Chart(buffered).vi to scan channel 1 of the RDA Server. The results were max scan rate = 220 kS/s, with a buffer of 50 kS, reading 10 kS at a time.


Benchmark Test 2
Use Cont Acq&Chart(buffered).vi to scan channels 1 and 2 of the RDA Server. The results were max scan rate = 130 kS/s, with a buffer of 50 kS, reading 10 kS at a time.



Benchmark Test 3
Use Cont Acq&Chart(buffered).vi – modified for two devices – to scan channels 1, and 2 of the RDA Server and channel 1 of RDA Client. AT the server, the results were max scan rate = 70 kS/s, with a buffer of 50 kS, reading 10 kS at a time. At the client, the results were max scan rate = 120 kS/s, with a buffer of 50 kS, reading 10 kS at a time.
The figure below shows how VI Logger can be used with RDA. The RDA feature of NI-DAQ is very useful in situations when a computer with a DAQ device is placed in a harsh environment where controlling or monitoring a process is necessary. Furthermore, this feature can be used to enable a central computer to acquire all of the data from several machines and then process or store that data. Finally, this feature adds no extra cost because it comes free of charge with NI-DAQ and because it uses the Internet – now almost a necessity for every company.

For more information on RDA, refer to the following application note: Developing Networked Data Acquisition Systems with NI-DAQ

Reader Comments | Submit a comment »

what happend if use daqmx whith pci-6250?... don't work.
- Jan 28, 2006

Great but need update
Hi I found this document very informative, however it can stand to be updated to include information on DAQmx. I still haven't found how handle remote acquistion, when my LV 7.0 code has been written using DAQmx functions. I'm off to search some more.
- Roman G. Boychew, Qualcomm Inc.. rboychew@qualcomm.com - Aug 13, 2004