Compact power meter offers low current measurement benefits

Compact power meter offers low current measurement benefits

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By eeNews Europe

The family consists of the Models WT310E single phase, WT310EH single phase high current, WT332E two-element and WT333E three-element versions.  The units offer enhanced measurement accuracy of 0.1% of reading +0.05% of range.  The WT310E provides low current measurement capability to 50 µA, and up to 26 ARMS.  The unit is aimed at the engineer doing Stand-by-Power measurements, Energy Star, SPECpower and IEC62301 / EN50564 testing, Battery Charger and other low level power measurements.

Many of today’s power conversion circuits use energy saving switching techniques.  These can cause distorted voltage or current waveforms with high harmonic content.  To measure these waveforms accurately, the WT300E series power meters use high resolution sixteen bit ADCs with a digitising rate of 100 ksample/sec.  They have an enhanced low frequency measurement capability of 0.1 Hz.  Overall bandwidth is DC and 0.1 Hz to 100 kHz,

The WT310EH is a single phase high current version with current ranges from 1A to 40 ARMS.  The bandwidth on this model is DC and 0.1 Hz to 20 kHz. The WT332E is a two element meter for use on split phase and three phase three wire circuits.  The WT333E is a three element meter for use on three phase three wire or three phase four wire circuits.  These models have current ranges of 0.5A to 20 ARMS, with low current measurements to 5 mA.  All models have voltage ranges from 15 to 600 Volts RMS, and low voltage measurement capability to 150 mV.

An optional Harmonic Analysis function is available for the WT300E series Digital Power Meters.  This will benefit the design and test engineer in product performance evaluation and for power quality conformance testing.  Both the Normal power parameters and Harmonic data are measured simultaneously providing for faster and more accurate power analysis.  Harmonic Analysis and THD Calculations can be made up to the 50th order from a 50 or 60 Hz fundamental frequency.

The Integration function measures Amp-Hour and Watt-Hour parameters.  This is mportant for stand-by-power measurements.  In the stand-by mode the current can be very low.  Then when the device goes to operation mode, the current can increase substantially. The new Auto Range feature will optimise the range setting for maximum accuracy measurements. Yokogawa’s ‘Average Active Power’ function makes it possible to measure power consumption under conditions where the power fluctuates greatly.  Watt-Hours are measured over some time period then the Time is divided out to leave an average power reading.  This is the industry preferred method for  Stand-by-Power measurements.

A feature has been added to the data update rate. The WT300E series can chase fluctuating input frequencies like motor by changing the data update rate automatically. The device can cover from the lowest 0.1 Hz input. Users can select ‘AUTO’ data update rate added to fixed settings of the previous models. The instrument can detect cycles of input signal automatically and measure it correctly.

All the industry standard communication interface ports such as USB, GPIB, RS232 and Ethernet are available for the WT300E series.  The standard interface is USB plus GPIB or RS232.  Ethernet is an available option.  Measured digital data from the WT300E series can be acquired by Yokogawa recorders via Ethernet or Modbus/TCP directly.  Yokogawa’s WTViewerFreePlus software is provided with each WT300E unit.  This permits displaying and saving the measurement data, numeric values, waveform display and trend graphs.  Also IEC62301/EN50564 software for stand-by-power measurements is available as a free download.

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