Evaluation Engineering - 11

Gibson elaborated on the three different modular test instrument platforms
that VTI offers. "The VXI platform provides
large-sized modules for high-performance,
high-density testing, typically in missioncritical, military/aerospace applications,"
he said, adding that VTI's VXI modules
are individually shielded to maintain signal quality.
Gibson said the LXI platform provides
a way to interface to external controllers
and workstations through the LAN interface. Because the platform does not have
dimensional requirements, the platform
can be more cost-efficient while offering
high-density and flexibility for switching
modules, he explained. "VTI LXI mainframes have an analog backplane for direct,
internal connection of multiplexed signals
to a measurement instrument, such as a
6½-digit digital multimeter," he said. "The
analog backplane maximizes signal integrity through the system and eliminates ex-

ternal wiring between switching modules
and a DMM."
Gibson said that with the PXIe platform,
modules can communicate with the backplane at up to 2 GB/s, explaining that PXIe
is suited for medium- to high-density automated test and data-acquisition systems.
"Modular test generally defines a capability in which measurement, stimulus and
switching functions specific to a test application requirement can be plugged into
the backplane of a chassis or mainframe,"
said Bob Stasonis, technical product specialist at Pickering Interfaces. "Modular
also implies that these plug-ins are easily
accessible by the end user (easy to insert,
easy to remove) to allow for simple and fast
maintenance."

Stasonis said modular test platforms
have been around for more than 30 years.
Some are proprietary, where only one supplier's modules can fit into the chassis. In
contrast, open standards such as PXI allow vendor interoperability, meaning any
vendor's PXI modules can plug into any
vendor's PXI chassis.
Proprietary modular platforms give
the supplier more flexibility to tailor mechanical and performance characteristics
that are specific to their offering, whereas
open platforms such as PXI offer a broader
range of instrumentation, giving the end
user more flexibility in creating a modular
test system, Stasonis said.
Craig Hughes, senior manager, instruments, Astronics Test Systems (ATS), defined a modular test architecture as an
adaptable design that can add or remove
functions by hardware and/or software
methods, allowing designers to configure a system to their needs. "When the
architecture is based on COTS components and standardized interfaces such
as LXI, PXI, USB, and VXI, the designer
is afforded additional choices, increased
availability, and lower obsolescence risks,"
he said. "Furthermore, ATS utilizes a synthetic instrumentation (SI) architecture
wherever possible."
"Modular test typically refers to a
class of switching and instrument solutions that require an external chassis to
function; the chassis provides power, a

high-speed backplane for communications and timing, and a controller," said
Jon Semancik, director of marketing at
Marvin Test Solutions (MTS). "Rack-andstack instruments, on the other hand,
integrate the desired functionality in a
standalone enclosure that typically only
requires line power and a communications interface."
Semancik said MTS designs and manufactures PXI-based instrumentation and
switching cards, in both 3U and 6U form
factors, with products offered with PXI
and PXIe interfaces. "PXI is the most
widely adopted modular test architecture in the industry, scalable from smaller
benchtop applications to large multibay
test systems," he said. "The ability to mix
and match 3U and 6U devices in a single combination chassis is also a major
advantage.
"We define modular tests as a combination of a wide choice of different hardware components on common buses
and a universal software API to access
these," said Oliver Rovini, technical director at SPECTRUM Instrumentation.
"SPECTRUM supports the PCIe, PXIe,
and LXI platform."
Each has its own advantages, according
to Rovini. "PCIe is common and can be
found in nearly every PC system; therefore, it's easy scalable from small low-cost
systems to high-end server systems with
massive GPU processing," he said. "PXIe

Astronics Test Systems ATS-3100 PXI integration platform.

MAY/JUNE 2020 EVALUATIONENGINEERING.COM

11
http://www.EVALUATIONENGINEERING.COM
Evaluation Engineering

Table of Contents for the Digital Edition of Evaluation Engineering
