SOFTWARE ISSUES
It doesn't matter if it's a PC-based waveform generator, logic analyzer, signal generator, spectrum analyzer, or scope. Engineers don't like to wade through "menu hell," as Jaynes calls it, to get a quick measurement. While they're okay for configuring a test stand, deeply nested menus slow the measurement process.
Ken Koehn, program manager of system components at Agilent, notes that his company holds most of its scopes' menu structure at no more than two levels deep. Unlike the earliest DSOs, Infiniium scopes maintain the look and feel of an analog scope. According to Monopoli, large touchscreens (8.4 and 10.4 in.) also help satisfy customers who demand easier-to-use scopes.
Another way to make digital instruments less complicated and less expensive is to let users buy the functionality they need—and no more. While Koehn says that Agilent's customers generally have been asking for more complexity in today's 8000 series, limiting installed software modules to fit their applications makes lots of sense.
For example, engineers who need to design and test GSM phones or LAN chips can download the appropriate personality modules and pay for them as needed. Engineers designing audio equipment don't care about jitter analysis and shouldn't have to pay for an unused feature.
STANDALONES VS. PROGRAMMING
NI's Darcy Dement, senior product manager of modular instruments, notes that design and test engineers performing measurements on the benchtop require interactive measurements to quickly verify their design and diagnose incorrect circuit behavior. Therefore, they often use traditional, standalone instruments on the benchtop to obtain "always on" performance and a fast time to measurement without programming.
Harpaz says that when programming is necessary, LabView Virtual Instruments (VIs) provide a way to collect data from various measurement devices, i.e., laser interferometers, capacitive probes, and other mechanical metrology devices. Danaher Motion's QA group uses LabView VIs to analyze and export machine metrology data, which measures variables such as the straightness, pitch, yaw, and accuracy of moving axes.
VIs have simplified instrumentation configuration. According to Fluke marketing manager Hilton Hammond, the U.S. Department of Defense continues to push a common VI platform so engineers can plug in digital multimeters (DMMs) from Agilent, Fluke, or any other vendor and have them work in the same system. Engineers simply don't want to spend time dealing with the intricacies of writing drivers and programming in C or Visual Studio.
While VI development can still represent a significant time investment, National Instruments shortcuts the process for benchtop applications. Its Express VIs minimize benchtop measurement configuration and programming while maintaining a fully customizable GUI and development environment. According to Dement, Signal Express is a fully interactive measurement environment for benchtopapplications (Fig. 3). It requires no programming, and it offers built-in instrument control, analysis, visualization, and data storage.
HARDWARE
Knowing what instrumentation hardware to use can save money. Walter Shawlee, president of Sphere Research Corp., thinks many companies are throwing money into higherend instrumentation when it isn't required. There's no reason to use a 6-GHz scope on analog audio or video signals when a 100-MHz, dual-trace scope will suffice, he says.
Shawlee also says that some of the high-end digital DMMs don't hold their accuracy as well as his older Fluke or Tek TX1, which are no longer available. Another engineer complained that his new DMM just doesn't update its display fast enough.
Here's Agilent's rule of thumb for selecting a DSO: signal bandwidth (Hz) = 0.5/signal rise time (s), and scope bandwidth = 2 signal bandwidth (for 3% errors). So, measuring a 1.0-ns rise time at 3% error requires a scope bandwidth of 1 GHz. For a fourchannel scope, multiply the scope bandwidth by 4 to get 4 Gsamples/s. On DMM update rates, says Koehn, today's DMMs manage 50,000 readings/s and can sample ac signals at 1.5 Msamples/s.
But wide bandwidths and fast sampling rates aren't the only important factors. Viren Javadekar, engineering manager of the Power Quality Correction Group at Schneider Electric, needs noise-free signals, isolation, and portability in a scope. He uses his Tektronix TPS2000 series scope to look for glitches and anomalies on threephase power systems.
A false glitch caused by noise can waste several days trying to solve a nonexistent problem. Because the scope has completely floating channels, there's no need for separate isolation devices between each phase and the scope's inputs. Javadekar employs the instrument on the bench in design and development, uses it on the plant floor for manufacturing testing, and carries it to sites for startup and troubleshooting.
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