The
need for higher data communications speed is the driving force behind the
evolution of Ethernet from 10MB/s up to 10GB/s bit rates. Currently, GB
Ethernet has four types of physical layer signaling: 1000Base-SX (short
wavelength optical fiber), 1000Base-LX (long wavelength fiber), 1000Base-CX
(short run copper) and 1000Base-T (100m, four pair category 5 UTP).
Some
applications that need the kind of speed delivered by GB Ethernet include:
-
Remote video monitoring of critical assets and operating equipment;
-
Machine vision systems for industrial production;
-
Real-time monitoring and control in processing and manufacturing industries;
and
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Remote data acquisition, test, measurement and data logging.
Industrial
Automation Applications
On the industrial side, high-resolution video
applications have been a leading force in seeking higher bit rates. This is due
to dense data content in high frame rate video, especially applications
involving full color. This applies to both visible light and infrared (IR)
cameras. In fact, full-color cameras with both visible light and IR imaging
capabilities are widely available, and can transmit images at full frame rates
of 400Hz and higher. These frames include not only images, but also temperature
measurements with 14-bit or higher resolution.
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Most
industrial video cameras used for machine vision automation and real-time
remote monitoring of critical equipment come with GB Ethernet Vision
capabilities. This includes the GB Ethernet Vision Control and Streaming
Protocols (GVCP and GVSP, respectively). These capabilities allow an automated
application to detect and enumerate the cameras and define how they obtain a
valid IP address. In addition, the application can configure cameras and
receive streaming data from them (bootstrap registers describe the cameras,
including current IP address, serial number, manufacturer, etc.). Some of these
applications take advantage of Power-over-Ethernet (PoE) to power the cameras.
Besides
machine vision and other production automation systems, these capabilities are
important in a variety of remote security, surveillance and monitoring
applications, which include: asset monitoring and protection (warehouses, bulk
material yards, etc.); process monitoring and control; machine condition
monitoring; high-speed sorting; assembly verification and package inspection;
and remote control of test and measurement systems.
Convergence
of Office IT and Automation
Besides
the need for high data transmission speeds, another driving force behind the
expanding use of GB Ethernet (and Ethernet in general) is reduced capital
investment costs. Instead of having separate redundant networks, there is one
shared data communication system across IT and automation. But an automation
environment has different cabling needs than an office IT environment. The
types of connectors and cables used in the office are not robust enough for the
factory floor. In order to successfully converge the two networks, passive
component requirements for both sides need to be taken into account.
The
ideal solution is to use cables and connectors that meet the data speed
requirements of office IT networks, and provide the robustness, flexibility and
ease of assembly needed on the factory floor. This approach allows the
resulting network to combine applications in a way that saves cost, increases speed
and improves efficiencies. The resulting flexibility also allows the system to
keep up with changing automation needs and future data rate increases that
office IT staff will be keen to adopt.
Cable
and Connector Selection
CAT5
cables and connectors are fine at the lower Ethernet data rates. CAT6 hardware
becomes a necessity for GB Ethernet. At GB Ethernet speeds, you can't view a
cable/connector interface as a lumped-element, but must treat it as a
transmission line. More specifically, the effects of cable and connector
capacitance can degrade the system's signal performance. Excess capacitive
loading can cause an impedance mismatch on the transmission line, signal
reflections and distortion. Using cable and connectors that have minimal
line-to-line and line-to-ground capacitance will help ensure an acceptable
amount of signal distortion.
For
example, Harting's line of RJ Industrial cables and connectors are suitable for
10GB Ethernet, and have features that facilitate the convergence of office IT
and factory automation systems. These designs evolved from the company's work
on 4-pole CAT5 applications several years ago. Through the use of patented IDC
(insulation displacement connector) technologies, the company's line of RJ45
and M12 connectors allow for tool-less field assembly.
It's
important to recognize that not all 8-wire cable is suitable for GB Ethernet.
The jacket material, core structure, agency ratings, shielding, environmental
ratings, etc. are all important considerations when selecting the correct cable
for the application. Many 8-wire Ethernet cables are only rated for CAT5
applications, and may or may not have the ratings and specifications you need.
These
considerations are particularly important when fabricating your own GB Ethernet
cable assemblies. You don't want to invest in CAT6 connectors and put them on
the wrong cable. Therefore, selection of Ethernet cables and connectors should
be made at the same time to ensure compatibility. For example, if shielded
cable is required, then you need to make sure the shielding continues through
the connector, i.e., the connector termination has to be compatible with the
cable.
Steve Loyal is business development manager, device
connectivity solutions for Harting North America.
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