USB finds its place on the factory floor
May 1st 2007 Technologies that are popular in the PC industry
usually end up making their way to the factory floor.
Serges Lemo, USB data acquisition product
engineer and Nipun Mathur, industrial data
acquisition product engineer at National
Instruments discuss the industrial use of USBs
Adecade ago, the introduction of
Ethernet on the factory floor was met
with considerable scepticism.
Engineers raised questions about its
communication reliability, connector
performance and hardware sustainability
under harsh industrial environments.
Ethernet evolved to overcome these
concerns and engineers are now
successfully using it in a variety of
industrial applications from mining to
offshore drilling. Ethernet has seen major
success because it is readily available on
commercial devices such as industrial PCs
and because it has an existing knowledge
base. Now, with the explosive growth and
adoption of USB in the PC industry,
engineers are evaluating the viability of
USB in industrial environments. USB has
been widely adopted as the standard bus
for PC peripherals because it offers ease
of use; high data throughput; and, with an
estimated 2 billion ports around the world
(usb.org), it is one of the fastest-growing
bus technologies in the computer industry.
Because of its broad adoption and high
performance, USB, like Ethernet, is finding
its place on the factory floor.
The need for USB in the factory
The typical factory floor is a mix of
sensors, actuators, relays, motors, wires
and controllers working together as an
interdependent system. Running an efficient
plant involves promptly troubleshooting
malfunctions and constantly evaluating
plant efficiency by monitoring machine
vibrations, capturing digital events and
trending temperature and pressure data.
Along with 24V digital signal levels, 4 to
20mA analogue signal levels and galvanic
isolation for safety, industrial applications
require a measurement system with highspeed,
accurate analogue input; fast data
logging; and analysis capabilities. They also
need a permanently installed efficiency
monitoring system and a portable
diagnostic system for troubleshooting.
Programmable logic controllers (PLCs)
traditionally used for plant control do not
offer the high-speed I/O required for
diagnosis and monitoring tasks. Instead, a
USB-based measurement system with
industrial I/O levels and high data
throughput can make demanding
measurements, including dynamic
machine condition monitoring. You can
use USB for short-term diagnostic systems
that require quick and easy setup. You can
also permanently install USB data
acquisition systems where industrial PCs
or human machine interfaces (HMIs) with
USB ports are available.
Ease of Use
One of the major benefits of USB is its plugand-
play ease of use, which promotes fast
setup times. Major OSs including Windows,
Mac and Linux offer built-in USB support,
and most industrial PCs, laptops and
industrial HMIs contain USB ports. After you
install USB device driver software,
connecting a USB device to a host
computer requires no action or configuration
other than physically plugging the connector
into the USB port. Because USB is hotpluggable,
you do not have to turn off the
computer to add or remove a device, and
USB bus power often eliminates the need
for external power. These features greatly
simplify setup and mobility, making USB a
good solution for portable and short-term
industrial monitoring applications.
High Performance
Machine diagnosis and monitoring can
require measurements from a large number
of I/O channels at high acquisition rates,
sometimes distributed across the factory
floor. Hi-Speed USB ports offer connectivity
for up to 127 devices with transfer rates of
up to 480 Mb/s. The USB standard defines
a maximum of 5m between the host
computer and the USB device. However,
with commercially available USB hubs and
extenders, you can extend USB up to 30m
or 500m, respectively.
Reliability and Security
Reliable communication in harsh industrial
environments is an absolute requirement for
industrial applications. USB data
transmission occurs over a twisted pair of
data lines with differential signalling. This
design reduces most noise that could
otherwise cause data errors during transfer.
In addition, to eliminate miscommunication,
error checking is built into the transfer
protocol. You can also use strain relief with
USB cables for increased protection and, for
mechanical reliability, some vendors offer
industrial-rated USB connectors with latches.
USB for the Factory Floor
High data throughput; ease of use; reliable
communication; and availability on
industrial PCs, laptops and industrial HMIs
have made USB an attractive bus
technology for industrial use. Many new
USB-based data acquisition systems are
being introduced that offer the right I/O
mixes for factory floor applications. For
example, National Instruments recently
released the NI CompactDAQ platform and
new bus-powered M Series devices for
USB. These devices feature built-in
galvanic isolation to protect plant assets,
the data acquisition system, host PC and
user from hazardous voltages. They also
offer panel and DIN-rail-mounting options.
NI CompactDAQ modules feature built-in
connectivity and signal conditioning for the
most common analogue, digital and
sensor measurements, including
temperature, pressure, flow and vibration.
Together, the plug-and-play ease of use
and high performance of USB make it
effective for both portable and fixedinstallation
applications. With a growing
number of USB-based industrial
measurement systems offering direct
connectivity to industrial sensors, USB is
getting ready to make an impact on the
factory floor. More articles from National Instruments UK Limited: | 
