Importance

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Abstract

The invention provides a signal conditioning stage for a photonic current or voltage transducer which comprises a number of burden resistors and a number of switches in parallel with the burden resistors, the switches operable to short different burden resistors in response to detection of different currents or voltages, and thereby protect the burden resistors and/or adjust the dynamic range of the transducer. The invention enables a hybrid photonic current or voltage sensor with an extended measurement range and increased accuracy and signal-to-noise ratio at the lower measurement end. Embodiments of the invention provide a device that is capable of covering both protection and metering ranges, as may be defined and re-defined from time-to-time by relevant standards. The invention also enables an auto-ranging device which increases measurement performance at lower current by deliberately reducing the range for lower currents and increasing the range when certain current level is exceeded, increasing dynamic range without the need for multiple LVTs. Similar range switching allows dynamic range increases in voltage sensing applications too.

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First Claim