Michal Brychta
Principal Applications Engineer, Analog Devices
C h a p t e r 2
A fundamental characteristic of the digital
factory is the interconnectivity of devices
on the factory floor. Between edge
devices, sensors, and other miscellaneous
field instruments, all devices vital to
the factory's operation are expected to
be interconnected to share data and
operational status.
Historically in process plants, often an
extension of the factory enterprise,
the prominent communication protocol
has been a 4–20 mA current loop. First
introduced in the 1950s, 4–20 mA works
by communicating a sensor output via
current signals ranging from 4 mA to
20 mA. While this protocol became an
industry standard for several reasons, a
major reason was its ability to support
communication over long, kilometer-range
distances, which are needed for process
plants.
Unfortunately, the 4–20 mA protocol
has become mostly antiquated and is no
longer a feasible solution on a modern,
high-speed factory floor. The 4–20 mA
communication protocol fails in that
it has inherently slow speed and only
offers one-directional communication.
SEAMLESS CONNECTED
FIELD INSTRUMENTS WITH
ETHERNET-APL
With Ethernet-APL, you have much
more bandwidth so you can transmit
more data and power to the edge.
With these benefits, the edge in a
digital factory is now capable of even
more things—including sensor fusion,
and even more sophisticated human-
machine interfaces—than would've
been possible with 4–20 mA."
10
Leading the Way to the Digital Factory
