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ScopeMeter® or Bench Scope? Why Not Both?

There are hundreds of programmable logic controller (PLC) drives throughout Linamar’s production facilities. A quick check of some of the relays with the four-channel handheld ScopeMeter® portable oscilloscope shows that everything is in good working order.

Leigh Copp, Advanced Systems Group Chief Engineer at Linamar Corporation, frequently uses a Fluke 190-204 ScopeMeter® portable oscilloscope to diagnose electronic components in the field. “Even if it can’t replace the large bench scopes, it does reduce the frequency with which we need to bring them into the field,” says Copp. “That is a big plus because I hate to risk dragging a bench scope on top of a machine where there is quench liquid spraying.”

But even with powerful ScopeMeter® capabilities, sometimes a bench scope is necessary; for example, when they discover an intermittent commutation fault where the positive and negative power semiconductors on one side of the inverter bridge are conducting at the same time. “This can be challenging because the transients on modern IGBTs and power MOSFETs are quite fast, while our output resonant frequency might be comparatively low,” says Copp.

In those cases the Linamar team brings out either the Tektronix TDS 3054 4-channel color scope, with 500 MHz, or the much larger TDS 7154. “The 3054 has one digitizer per channel so you don’t sacrifice any of the bandwidth or sampling speed when you’re running four channels. When we need more memory we bring out the 7154, which has deeper memory to capture the higher frequency components of the device switching voltage and current, and still provide visibility into the lower frequency events leading up to the fault,” he adds.

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