Text preview for : 2649 Test Bench Today.pdf part of Keithley 2649 Test Bench Today Keithley Appnotes 2649 Test Bench Today.pdf
Back to : 2649 Test Bench Today.pdf | Home
A G R E AT E R M E A S U R E O F C O N F I D E N C E Another integrated feature is some type
of source unit. In the past, test engineers had
to link power supplies and/or signal genera-
tors together with a measuring instrument,
such as a DMM. Now, there are single units
available that both provide source signals
and can measure and record results. Some of
these instruments have two or more channels
for even greater density and flexibility.
Along with increased integration comes
The Test Bench Today the demand for more specialized instru-
ments. For instance, some oscilloscopes
feature specialized interfaces for testing
newly emerging serial buses. On the other
What designers and test engineers hand, some cutting-edge applications de-
need from a test-bench instrument mand entirely new tools and features. The
field of nanotechnology research and devel-
opment demands instruments that can meas-
ure extremely small quantities in the range
Dale Cigoy, Keithley Instruments, Inc. of nanovolts and below, accurately and re-
peatedly. Nanotechnology research also de-
P
mands highly accurate and stable sources of
hoTos of a typical test bench usu- test (DUTs). Most DMMs now also include arbitrary waveforms. Many instruments can
ally show rows of boxes stacked a storage buffer with the capability to store now offer the precise and stable waveforms
several feet high with a maze up to 450,000 readings. A scan and storage necessary for nanotechnology applications.
of wires, cords, and test leads capability is a key option for test engineers.
curling around the benchtop. A They can now use the full functionality of New interfaces
typical test-bench contains a number of in- the DMM and the multipoint testing capabil- The growth of the Internet and the World
struments necessary to engineers designing, ity of the built-in scanner and store collected Wide Web has also impacted test instru-
developing, and testing new product designs. data, or it can be retrieved for a more real ments. Web-enabled instruments are fairly
As a result, to get all the necessary function- time update of data. The latest DMMs can be common today. Most of these instruments
ality, several different types of instruments configured as full data acquisition systems to contain an Ethernet connection that lets the
may be needed, including voltmeters, current switch, read, and store data. instrument talk to a PC or connect to other
meters, ohmmeters, voltage and/or current
sources, and frequency generators.
However, newer generations of instru-
ments combine many, if not most, of the
functions found in stand-alone instruments
into one box. This article looks at the chang-
ing world of benchtop instrumentation.
New instruments
The biggest and most notable change in
the design and manufacture of newer genera-
tions of benchtop instruments is increased
integration. Traditionally, digital multimeters
(DMMs) were multi-function devices that
measured voltage, current, and resistance.
Now, they can measure more parameters.
Most DMMs can handle frequency and tem-
perature, for instance, including parameters
for specific diode and transistor tests.
Later generations of DMMs included
Figure 1. Series 2600 System SourceMeter(R) instruments offer electronic component and semi-
scanner cards that let them switch from point conductor device manufacturers a scalable, high throughput, highly cost-effective solution for
to point in a circuit or to several devices under precision DC, pulse, and low frequency AC sourcemeasure testing.
The Test Bench Today: What designers and test engineers need from a test-bench instrument October2005
instruments to form a complete data-acquisi- PC. Virtually all desktop and laptop PCs on ter Analysis Software from Tektronix is used
tion system. Most Web-enabled instruments the market come equipped with USB ports. with its oscilloscopes to capture and analyze
contain a built-in Web page with a specific These ports have full software support under data and make accurate jitter measurements.
instrument URL. The Web page allows us- common operating systems such as Windows Along with increased use of software and
ers to read and set network parameters, such 2000 and XP. programmability options, there are a host of
as IP address, MAC address, and calibration For test and measurement applications, standard communication interfaces available
dates, and to send commands to and query USB offers some significant advantages. to ease transfer and collection of recorded
data from a unit. USB provides users with a simple means of data. One of these is VISA. This is a soft-
Another advance in interfaces comes developing test and measurement applica- ware layer that standardizes communication
later this year with the LAN extensions for tions by offering advantages over PC plug-in between test instruments and different buses
instrumentation (LXI) through the work of boards. These include plug-and-play capabil- such as GPIB, serial links, Ethernet, etc. It
the LXI Consortium. Basically, LXI is an ity, better noise immunity, cost savings, and allows programmers and users to choose dif-
Ethernet-based communications standard portability, among others. ferent buses for communication within the
for small, modular instruments with or with- USB offers full- and high-speed data same program.
out front panel control or on board display. transfer rates. Computers configured with Another is IVI. This is a level of standard-
LXI instruments are designed to operate USB 1.1 ports can transfer data at up to 12 ization for instruments of the same type, i.e.,
with Ethernet as the system communications Mbits/second. For high-performance ap- DMMs, sources, etc. It is another layer on
backbone. The Consortium's goal is to define plications, high-speed USB 2.0 ports boast top of VISA. For instance, this lets a DMM
a common instrumentation standard to offer speeds of up to 480 Mbits/second. from Keithley respond to the same calls as a
flexible packaging and tight integration ad- DMM from Agilent.
vantages of proprietary modular instruments software and programming
without the physical constraints and added More and more instruments now come Adapting to a rapidly changing
cost of card-cage architectures. The plan is equipped with software so that users can de- world of test
for the LXI standard to evolve and take ad- velop application-specific test routines and Today, test bench instruments need to be
vantage of current and future LAN develop- execute them from either the instrument itself easily and quickly customizable for a number
ments that go beyond the basic connection or from a PC. Only a few years ago, software of different measurement tasks. Flexibility is
capabilities of legacy test and measurement to control rack and stack test systems was a must, especially with shorter engineering
systems including web-style interfacing, lo- used mostly in production applications. Con- cycles and tighter instrumentation budgets.
cal and wide area networking, and precision necting a computer to an instrument to log A basic instrument can be tailored to any
timing synchronization capabilities. data provides records of test data, which ISO number of specific measurement tasks with
As for other communication interfaces, and other standards are making necessary. the help of embedded scripting. Basically
IEEE-488 or GPIB is still a dominant net- Some examples of software that ships this allows an instrument to execute a speci-
work, partly because it has been around for with test instrumentation include Test Script fied number of source and measure functions
nearly three decades and, as such, is built Builder (TSB) and LabTracerTM software for repeatedly. For instance, an individual in-
into many, if not most, instruments on the Keithley's Series 2600 SourceMeter