“Precision Power Scope” – combines power-analyser and ‘scope measurements
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 500th, 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 and display of voltage and current across all three phases. Up to 16 different waveforms – including voltage, current and power – can be displayed side-by-side, giving engineers instant “snapshots” of performance. Derived parameters, such as root mean square (RMS) and mean power values, enable the identification of cycle-by-cycle trends.
The PX8000 incorporates Yokogawa’s isoPRO technology for isolation performance at the highest speeds. isoPRO core technology, designed with energy-saving applications in mind, delivers the performance needed to evaluate high-efficiency inverters that operate at high voltages, large currents and high frequency. Optical isolation allows safe operation of the instrument when the measured voltages may be far above ground.
Also possible is an X/Y display capability which can be used, for example, to show the speed/torque characteristics of motors. It can also display Lissajous waveforms of input and output for phase analysis. PX8000 incorporates a history memory function that automatically records up to 1000 historical waveforms: 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.
A variety of functions including arithmetical calculations, time shifting and Fast Fourier Transforms enable users to display waveforms with offsets and skew corrections. An automatic de-skewing function eliminates offsets between current and voltage signals that may be caused by sensor or input characteristics. Users can also define their own computations via equations that combine differentials, integrals, digital filters and other functions. The unit can 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.
The PX8000 comes with an accompanying PC software application called PowerViewerPlus that can be used to capture waveform data for further analysis. This extends the number of data points it is possible to analyse, making the PX8000 ideal for capturing and analysing longer-term performance.
Typical application sectors include inverter and motor testing, reactor loss measurement of inverter boost circuits, transient responses of industrial robots, wireless charger efficiency measurement, and voltage and power measurements in electricity distribution systems. At the low-power end of the spectrum, you might also use the instrument to measure detailed power-drain from battery-based products, to identify transient conditions and extend battery life.
Yokogawa; www.tmi.yokogawa.com/px8000
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