Profibus, Modbus, EtherCAT, DeviceNet,
or even custom protocols.
Also, the nature of many industrial
applications has a wide variety of harsh
environments that they have to survive in,
including extended temperature ranges,
shock and vibration, high humidity, unre-
liable power, and intermittent connectivity.
And a characteristic of the typical indus-
trial operator is to run the equipment for
as long as they can, even though there may
be a “better” solution, to reduce costs by
using already amortized equipment until it
dies. Further complications that are often
encountered in industrial infrastructure is
that the solution may have been designed
30 years ago and all of the designers
have moved on or retired. This leaves the
current operators with a large number of
unknowns when they start contemplating a
phased rollout of a new sensor system.
Fortunately, the sensor marketplace
now offers a broad selection of alternative
approaches. Many aging analog compo-
nents have now been replaced with micro-
electromechanical systems (MEMS) that
are much more robust, smaller, and more
power-efficient than their original counter-
parts. Often, these sensors are already de-
signed to take advantage of new communi-
cations media such as LoRaWAN, NB-IoT
cellular, Sigfox, or even Wi-Fi.
As much as the industrial operator
may want to continue to use their existing
cable plant, that may not be practical. Old
industrial communications interfaces may
not be practical for the updated sensor
systems. Even if they are available, they
may be cost-prohibitive. A set of trade
studies will need to be undertaken to de-
termine the most cost-effective commu-
nications approach. If the decision is to go
with a wireless solution, then the designer
will need to investigate the practicality of
the solution given the physical character-
istics of the system to be upgraded.
Before beginning any significant up-
date of an existing system, the designers
should conduct a simple prototype test
that reproduces as many of the opera-
tional constraints as possible. This can be
accomplished using one of the many de-
velopment kits available on the market.
If we plan to replace hardline wiring
with a wireless solution, there will needto be a site survey in the radio frequency
(RF) spectrum to make sure that the fre-
quency bands will work for the applica-
tion. Oftentimes, industrial applications
will require large motors or other sources
of RF interference. This sort of survey
should be performed before the radio
selection so that the printed-circuit-board
(PCB) designers and software developers
will have sufficient information to make
informed decisions about the wireless
approach.
The process of upgrading brownfield
applications with new physical sensors will
often begin with the verification of the new
sensors at the silicon designers. Referred
to as physical verification, this process
involves a number of electronic design au-
tomation (EDA) tools, including a design
rules check (DRC), layout versus schematic
(LVS), electrical rule check (ERC), exclu-
sive OR (XOR), and antenna checks.
Fortunately, there are many co-design
suppliers that provide an automated suite
of tools to perform these checks. The
verified design will then be handed off to
a silicon foundry and the circuits will be
produced using an appropriate fabrica-
tion approach to meet the requirements
of the original design. From here, the
packaged chips go off to a PCB designer
for board-level design.
For highly sensitive or mission-criti-
cal applications, the PCB designer must
ensure that there exists a validated and
audited supply chain. In the past, there
have been documented cases of counter-
feit chips, typically with lower quality and
higher-than-normal chip mortality issues,
which compel developers of board-level
solutions to verify that the component
suppliers are meeting the reliability re-
quirements for the components.
Once the board-level solution is ready,
it will need to be subjected to a series
of environmental tests to validate the
performance in the environments where
the sensors will be deployed. This includes
thermal cycling, shock and vibration test-
ing, RF emissions and susceptibility testing
(including FCC certification), and a host
of other tests depending on the severity
of the environment where the sensor will
operate. For some applications, such as
high humidity, the boards may also need tobe conformal-coated or “potted” to protect
the circuitry from the environment.
Assuming that the sensor application
will use some sort of microcontroller or
other processor (often needed for the
encryption of communications or man-
agement of the wireless solution), the
software design team will need to make
a broad spectrum of decisions about
whether or not an operating system will
be needed, the software design philos-
ophy, the communications protocols,
and how to handle security. In addition,
if this is a brownfield application, the
software team will need to consider the
compatibility with the existing system
and the data-collection endpoints.
Security is a particularly tricky issue
because we need to make allowances for
software updates in the field, provision-
ing the sensors/radios, use of encryption
keys, etc. No matter how many steps we
take to thwart access to the device, we
must assume that the device has been
compromised by the time that it reaches
the field. This puts a special burden
on the provisioning approach to make
the device as secure from a software
perspective as possible. This will require
the generation of digital certificates and/
or the use of security circuitry such
as smartcard chips for secure key and
parameter storage.
To summarize, the update of a brown-
field industrial application will require that
the designer takes into account a broad
spectrum of design criteria. This ranges
from the desired compatibility with exist-
ing systems to the rollout of the platform to
even the supply chain if the application is
part of the critical infrastructure.
If the plan is to replace existing cabled
solutions with a wireless approach, the
designer will need to perform a number
of tests to ensure that the RF frequencies
will propagate as expected at the site.
And the designer would do well to incor-
porate security mechanisms throughout
the system to protect it from would-be
attackers. The application upgrade will
not be a simple task. But paying close at-
tention to the details will result in a new
solution that can both replace aging ex-
isting equipment and provide significant
cost savings moving into the future. ☐6 OUTLOOK Innovations impacting products, technology, and applications
JANUARY 2019 • electronicproducts.com • ELECTRONIC PRODUCTS