Five Things to Know about Ethernet/LAN Instrument Control
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A Local Area Network (LAN), or Ethernet, platform is the ubiquitous standard for networking PCs and connecting to the Internet. With the ability to span long distances, it also has become a popular instrument control bus for taking measurements from distributed or remote locations. When using Ethernet in your next instrument control system, remember these five tips to help ensure system performance, security, and longevity.
System Throughput Is Dependent on All Connected Devices
Ethernet is a shared communications bus; therefore, all connected devices must share the available bandwidth. This means that while an instrument may be capable of transferring data at 100 MB/s, it will often transfer information at only a fraction of that speed if it must compete with other computers or instruments. To ensure the highest system performance, you can create a secondary dedicated network for your instrumentation that does not have to compete for bandwidth.
It Is Important to Consider Possible Instrument Security Issues
Many of today’s instruments are full PCs running Microsoft Windows. While this OS offers greater instrument flexibility and onboard analysis capabilities, it also makes your instrumentation susceptible to the same viruses and malware that plague PCs. For ultimate system security, it is best to develop a separate network for your instrumentation that is sheltered from outside networks. If you must connect to a public network, keep your instruments up-to-date with the latest antivirus software and contact your IT department to determine if you should take any other security precautions.
VXI-11 Simplifies Instrument Communication
There are many different protocols for communicating over Ethernet, such as TCP, UDP, and RPC. To help simplify instrument control, the VXIbus Consortium developed the VXI-11 standard, which provides a GPIB-like interface for programming instruments over Ethernet.
You Can Communicate over LAN from Your Current GPIB Instrumentation
Instrumentation can be expensive, and it is difficult to justify buying new instrumentation just for Ethernet communication. With GPIB converters, such as the NI GPIB-ENET/100, you can get the benefits of distributed measurements from your current GPIB instrumentation.
Industry-Standard Software Interfaces Help Ensure Test System Longevity
The computer industry is constantly evolving, and in five years, a better bus may exist for distributed instrument control. To help ensure the longevity of your test system, it is important to make decisions that facilitate your system’s ability to adapt to new communications buses.One way you can do this is by using National Instruments LabVIEW Plug and Play instrument drivers and the Virtual Instrument Software Architecture (VISA). These technologies abstract the communications bus and provide a standard programming interface, regardless of whether you are using GPIB, USB, or Ethernet. As long as the programming commands for an instrument do not change, you can switch between communications buses with little or no code modifications.
Learn more about controlling your instruments over Ethernet and other communications buses.
This article first appeared in the Q3 2007 issue of Instrumentation Newsletter.
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