Integration is the key for accurate power measurement

06 February 2014

Yokogawa has combined power analyser and oscilloscope technologies to create a new instrument that can capture voltage and current waveforms precisely.

Yokogawa has combined power analyser and oscilloscope technologies to create a new instrument that can capture voltage and current waveforms precisely.

The PX8000 brings oscilloscope-style time-based measurement to power measurement. It can capture voltage and current waveforms precisely, opening up applications and solutions for a variety of emerging power measurement problems.

Being able to accurately measure power is becoming more important in all areas of design. For instance, EU member states are currently behind in their attempts to meet renewable energy targets for 2020. Precise measurement would allow engineers to design products that would allow more energy efficient energy capture, transformation and distribution. There is also a need to meet regulations, such as ErP for product standby power and SPEC for datacentres.

The new instrument has 12-bit resolution with 100 MS/s sampling and 20 MHz bandwidth. It provides simultaneous voltage and current multiplication to give real-time power sampling, supporting both transient measurement and numerical values averaged across the sample period. Up to 16 different waveforms can be displayed side-by-side, giving engineers instant “snapshots” of performance. The PX8000 has built-in functions for the direct calculation of derived parameters, such as RMS and mean power values, to enable the identification of cycle-by-cycle trends.

The PX8000 is customisable by the addition of modules. There are three types of modules; voltage, current and auxiliary. The voltage and current modules are used in combination for accurate power measurement. The PX800 can measure and display voltage and current on three inputs simultaneously, which is essential for engineers measuring three-phase electrical systems. The voltage and current modules can make measurements at up to 1000 V RMS and currents up to 5 A RMS respectively, with an accuracy of ±0.1%. Higher currents are possible with an external current shunt.

The auxiliary module is capable of 12-bit sampling at 100MS/s with up to 20MHz bandwidth. The module is intended for torque and speed measurements from sensors. There is a variety of input capabilities, including up to 200Vrms direct input, up to 1000Vrms via probe input and a pulse input from 1.8Hz to 1MHz. Accuracy of the auxiliary module is 0.5% of range. Up to three auxiliary modules can be installed on the PX8000 at one time.
The instrument also supports the capture of power waveforms over specific periods of time through the definition of start and stop cursors. This allows the examining of transient phenomena and also in the design of periodically controlled equipment. To ensure that such equipment complies with energy standards, it is vital to measure power consumption across a range of different modes from sleep to full activity and all states between.

The PX8000 uses Yokogawa’s isoPRO technology to deliver the performance needed to evaluate high-efficiency inverters that operate at high voltages, large currents and high frequency. The instrument incorporates a history memory function that automatically records up to 1000 historical waveforms which can be recalled and redisplayed. Recorded waveforms can also used to redefine trigger conditions. Historical waveforms are explored via condition-based searches to locate specific hard-to-isolate abnormal phenomena during repeated high-frequency measurements.

It is possible to simultaneously measure the harmonic components of voltage and current waveforms as well as the harmonic distortion factor. Harmonic measurements take place in parallel with conventional voltage and current measurements. Harmonics up to the 500th order of the fundamental can be measured.

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