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Tektronix TDS 744A Captures Troublesome Signal for Sharp's Color Word Processor

Faced with a time-consuming and troublesome triggering problem, Katsunori Hirano, Assistant Manager for Sharp Corporation's OA Systems Department, chose the Tektronix TDS 744A oscilloscope to identify and isolate the problem waveforms.

Sharp Corporation manufactures color word processors that have optical character recognition (OCR) and pen editing, which allow customers to create brochures using templates, illustrations and photographs. Personal computer functions can also be performed by touching icons with a pen. Hirano and his team had observed some noise in these word processors, but were unable to isolate the responsible waveforms. They were confident that the problem was in the pen-input area, but due to all the interfering noises, they couldn't identify valid signals.

The word processor system takes signal input from the pen and converts it to a digital signal, or code, making it especially difficult for Hirano's team to locate the troublesome noise. Once located, to capture the noise, the team must set the trigger (the time and level) precisely. This is a very time-consuming task because of the intermittent nature of the noise. Using an analog oscilloscope does not solve this problem either because the waveform display disappears too quickly.

According to Hirano, it was the InstaVuTM acquisition capability that was the key to their isolating the troublesome waveforms. A major disadvantage of conventional DSOs is the small fraction of time they actually spend capturing waveforms. Although their displays "look" lively, they actually capture as little as 30 parts per million of real-time events. Much, especially the glitches and abnormalities the user is searching for, can be missed. Another disadvantage of conventional DSOs is after each acquisition there's a pause while the display image is built. InstaVu acquisition eliminated both of these bottlenecks. Consequently, the user can capture glitches that were either previously too difficult to capture, or never knew existed.

"The key features of Tektronix' TDS 744A scope are that with its fast 1 GS/s sample rate it can capture 400,000 waveform acquisitions per second and it can repeatedly display the waveform on the screen, which was especially important to us for making comparisons," says Hirano. "Moreover, four channels can be seen simultaneously on the TDS 744A. This would be a great help in timing, which I'd like to try someday soon."

For now, Hirano is quite pleased with the results. They had a problem identifying and capturing certain troublesome waveforms, but with the TDS 744A oscilloscope and its InstaVu acquisition capability, they were able to isolate and analyze the signal anomalies. Hirano concluded that their primary benefit was the ease of pushing the InstaVu button and clearly "seeing" the noise that they were seeking.