New LFR complements CWT from PEM

Citation

(2009), "New LFR complements CWT from PEM", Microelectronics International, Vol. 26 No. 1. https://doi.org/10.1108/mi.2009.21826aad.011

New LFR complements CWT from PEM

Article Type: New products From: Microelectronics International, Volume 26, Issue 1

A new LFR ac current probe with market leading low frequency performance has been introduced by Power Electronic Measurements Ltd (PEM). This compact, low cost, clip-around probe is both flexible and dual-range, while being optimised to give minimal phase measurement error at frequencies from 45 Hz to 20 kHz. This is a Rogowski current probe, similar to PEM’s highly successful CWT range, which covers 1 Hz to 20 MHz.

The LFR unit is ideal for use as a general purpose power frequency ac current probe and can be used with oscilloscopes, acquisition cards, data loggers, power analysers and meters. Other typical applications include power measurement, leakage current and power quality where minimal phase error, low noise and good accuracy are key measurement criteria.

All Rogowski current probes generate noise, but the noise floor of the LFR is very small, and the LFR1/15 model is only 2.0 mVrms on the 300 A range. The rated output voltage is 6 V peak for a 300 A peak current, thus at 20 percent rated current the noise contributes less than 0.1° additional uncertainty to the phase error. This is better than a measuring class 0.5 current transformer. The same unit with peak current rating 300/3,000 A and coil length of 300 mm has minimal phase measurement error at 50 Hz of <0.35° and at 20 kHz of <1.8°.

Each probe is supplied with a traceable calibration certificate, with the probe calibrated to an accuracy of ±0.3 percent of reading with a conductor central in the LFR coil loop. If the conductor is large and fills the coil area, or the conductor can be kept central, the overall accuracy will approach the calibrated value. Even if the conductor is not central the LFR’s accurately wound and toleranced coil keeps the variation in accuracy with position to typically ±1 percent.

The LFR has all the established benefits of a Rogowski probe. A flexible, clip-around coil of only 8.5 mm thickness enables measurement in confined spaces or with otherwise difficult to reach cables and busbars. The probe is non-intrusive, very linear with current magnitude and frequency, undamaged by overloads and the coil size can be specified independently of current magnitude.

The instrument can be specified with coil lengths 300-1,000 mm as standard, with longer coils also available. It is EN61010 safety compliant, and can be powered by either a single 9 V battery or an external 12/24 V DC supply, with alternative power supplies also possible. It features a dual range switch allowing very wide dynamic measurement ranges from 60/600 A to 6/60 kA. It is also suitable for operation within a temperature range of −20 to +70°C.

For further information, please visit the web site: www.pemuk.com