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New ScopeCorder Reduces R&D Testing Time By 50%by Brad Byrum, Electronic Engineer, Yokogawa Corporation of
America Until a year and a half ago, electronic component manufacturer MGE UPS Systems, Inc., Costa Mesa, CA, used a traditional, 8-bit oscilloscope and a paper chart recorder in their R&D department. Setting up both instruments was tedious and time-consuming, and they often had to be connected to other components such as transformers or isolation probes. As a result, essential data required for testing often could not be captured. MGE produces UPS units for the 50 Hz, 750 KVA marketplace worldwide. Testing UPS units using a traditional oscilloscope is difficult due to the oscilloscope's low measurement resolution, which at only 8 bits or less limits the accuracy of the test. Technicians were only able to get rough voltage estimates because of the poor resolution that traditional 8-bit oscilloscopes offer. "We had a hard time measuring micro fluctuations in voltage with the old oscilloscope, and that is a very important measurement when we test our UPS units," said Trent Miller, senior test technician at MGE. "A fraction of one volt is very important to our UPS tests, since it can affect on-and-off switching." The average memory of most oscilloscopes is 32K, which limits the amount of viewable data for any given event. Thus MGE's technicians had trouble monitoring long periods of activity with accuracy: They were able to see the big picture, but were not able to zoom in on smaller details. These problems could only be remedied using state-of-the-art instruments. "I did a lot of research on what equipment was available and what each instrument could do for us," Miller recalled. He eventually found an instrument ideally suited to the testing -- the DL708 ScopeCorder by Yokogawa. The device combines the functions of MGE's paper chart recorder and digital oscilloscope into a single unit. Single Unit Solution The DL708 offers many features that exceed those of traditional oscilloscopes and provides users with totally new options. This model includes eight isolated input channels, a variety of plug-in modules, a 10.4-in. color display screen, 12-bit resolution, an internal 8-MB memory, and a built-in printer -- all in a small, portable 15-pound case. Miller found that the DL708's 12-bit resolution increased measuring accuracy making it "easy for us to measure minute voltage fluctuations," Miller stated. The new instrument increased signal accuracy, giving users a much better idea of what is going on in the circuit. Also, with the improved resolution users get better detail and can see what the signal actually looks like. Where the old 8-bit oscilloscope gave them about 256 points of data, they now have 4,096 points. In addition, there is a 16-bit module that shows 65,536 points if needed. With 8MB of memory, Miller and his associates now easily monitor long periods of activity, while maintaining a very high sampling rate. When noteworthy events take place during the test, the ScopeCorder easily captures them. The additional memory also allows a higher volume of sampling. Technicians zoom in on very specific parts of circuits to check details that were previously unavailable for viewing. If an operator examines a time event that takes one second, at 32K he will get only 20,000 data points, whereas with 8MB 5 million data points are available. "The DLs have so much memory that we can now capture data at a very high rate of speed, about 10 times faster than the old recorders," Miller commented. "We can run it for a long time and see how certain events are happening in sequence, which is very helpful when we test our UPS units." Another problem with traditional oscilloscopes is their lack of isolated inputs. Using an oscilloscope without built-in high-voltage, isolated inputs can be dangerous when testing certain types of circuits. MGE test technicians often risked shocks when their old style oscilloscope was floating with the ground prong removed. The isolation module on the ScopeCorder is one of the best features of this machine, according to Miller, adding, "We can put the probes anywhere we want without worrying about a ground loop. This is a big relief for all the testers." R&D Savings Prior to purchasing the ScopeCorders, MGE engineers were hard-pressed to complete their UPS research quickly and easily. We would set up our old paper chart recorders, input the data, and then the recorders would print all the information out on paper, Miller recalled. "The test was a one shot deal. If we didn't catch what we wanted, we had to reset the oscilloscope again and run another test. If we were doing a destructive test, we had to fix the unit and then try the test again, which was very time consuming. We also wasted time connecting the recorders to a step-down transformer or a variety of different probes." Miller found that the DL708 gave him not only real-time data storage like the old recorder, but data that could be spooled to an internal hard drive in the unit as well. Additionally, he explained that setup and operation of the ScopeCorders is very user-friendly. Miller can now measure several different points simultaneously, as opposed to using the old devices individually. For example, operators had to know how to trigger the old oscilloscope and then do several sample shots. When checking seven or eight different spots, they would have to check them one by one. With the DL, they clip onto all the different points and the information quickly and simultaneously streams in to the instrument. When technicians used the old oscilloscope, minimum measurement options were available with only two channels. Therefore, using one channel to trigger the system, the technician had only one channel remaining for testing. Also, the old oscilloscope had only one reference point as a timing base, meaning that the operator could only examine two or three spots, and if nothing was found the search had to be moved to another location. "Instead of having access to just two channels on the old oscilloscope, we have six on the new one, which gives us a lot more versatility when looking for a problem in the circuit," said Miller. "We can now test many different locations, then check to see how different areas relate to each other by calling up different screens very quickly." Most important to the management at MGE has been the time and money savings realized by the DL708s. "We can now do our tests three to four times faster than with the old equipment," Miller emphasized, allowing a savings of 50% of the time that they were spending on measurements. Having "two devices in one" is a cost savings, too. MGE's old oscilloscope cost $8,000, the chart recorders were $10,000 with a 250-volt input, and a probe to step it down cost $200, for a total of approximately $18,000. The DLs cost about $10,000 -- a significant savings. About the author: Brad Byrum is an electronic engineer and General Manager of the Test and Measurement division at Yokogawa Corporation of America. During his nine-year tenure, he has provided technical customer support, product management, and helped in the design of new test, control, and measurement products. For more information, contact Yokogawa Corporation of America, [dfx/incl/99dfx.htm] |
