“Precision Power Scope” - combines power-analyser and 'scope measurements

January 16, 2014 // By Graham Prophet
Yokogawa has tightly-integrated power-analyser and oscilloscope technologies to create what the company believes is a new class of instrument, that will add the time-based approach of the scope to the detailed power analysis of a dedicated analyser.

The PX8000 takes the form of a mainframe that hosts up to eight measurement modules. The mainframe is essentially a digital host platform that presents oscilloscope-style waveform displays, of either measured or calculated parameters, and/or numerical values (similarly of voltage and current, or power, harmonics, or a broad range of power-related figures); or graphical trend information extracted from the basic measurements.

Each measurement module (there are three at launch; voltage, current and sensor/auxiliary inputs) is a measurement sub-system with sampling at 100 Msamples/sec, and 12-bit A/D conversion, that passes timed measurements across an optical isolation barrier to the host unit. You use V and I modules in pairs, to provide data sets for power computations. The input modules cover voltages up to 1000 V RMS and currents up to 5 A RMS (higher values are possible with external current sensors), with basic accuracy down to ±0.1%. The analogue bandwidth, viewed as a scope-style system, is 20 MHz. The instrument can compute harmonics up to the 500 th, based on a fundamental of up to 6.4 kHz, as well as a broad range of other parameters such as power factor, efficiency and distortion.

You can use all of this functionality together with the waveform display; if you place start and top cursors on the waveform (of a stored, captured waveform) the instrument will calculate the suite of power measurements over that exact interval. Combined with an advanced triggering facility, with logical combinations of trigger conditions, this enables detailed power analysis of transient conditions that would be very difficult with a combination of conventional oscilloscope and power analyser, Yokogawa asserts, referring to, “...high-accuracy time-based power measurement: a need that conventional power analysers and oscilloscopes were never designed to meet.”

To evaluate three-phase electrical systems, at least three power measurement inputs are required. The PX8000 can accommodate 3-wire and 4-wire connections, and has pre-configured measurement setups for each, allowing for simultaneous capture