Monday 28 June 2010

De-skew correction

De-skew correction enhances accuracy of oscilloscope-based power measurements

High-frequency power measurements can now be carried out with greatly enhanced accuracy using a de-skew correction signal source, along with voltage and current probes, in conjunction with the /G4 power measurement option on the Yokogawa ranges of digital and mixed-signal oscilloscopes.

Even though power measurement using an oscilloscope is fundamentally less accurate than using a digital power meter, it offers much higher bandwidth. It is particularly suitable for measuring high-frequency switching losses in switched-mode power supplies. It also provides a power measurement capability using a general-purpose product which has other uses, an option that may be more acceptable to users who are not ready to invest in a true power meter or have limited budgets for test equipment.

The de-skew correction signal source is an accessory which is specifically designed to maximise the measurement accuracy of oscilloscopes when they are used for power measurements involving fast switching devices and high-frequency waveforms.

To correctly measure power-supply parameters such as power, impedance, power factor, watt-hours and ampere-hours from the voltage and current under analysis, the voltage and current signals must be applied to the signal input terminals of the oscilloscope with no difference in the transfer time. The signal source corrects the potential delays between voltage and current channels in combination with the auto de-skewing function provided as part of the /G4 option.

The unit produces an output voltage from 0 to 5 V and an output current of 0-100 mA (for low-current measurements) or 0-1 A (for high-current measurements). It has a fall time of approximately 25 ns (low current) or 250 ns (high current). The fixed time difference between voltage and current is 2.3 ± 0.5 ns (low current) or 14.5 ± 1.0 ns (high current). Its power supply of 5 V DC/100 mA is taken from the oscilloscope via a USB cable.

The de-skew correction signal source supports through-type current transformers and a variety of clamp-on current probes.

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