Kelvin Hagebeuk, Yokogawa Europe & Africa, discusses a relatively new portable instrument known as the ScopeCorder. As its name implies, it combines the features of an oscilloscope and a data acquisition recorder
With today’s increased incorporation of power electronics and switching devices in overall system design, there is a need for accurate measurement of both the power behaviour of the applied power electronics and other interrelated electrical and physical parameters. These might include inputs from rotary encoders, sensor outputs that require signal processing or linearisation, and derived electrical units such as real power, energy used or RMS values.
A deeper insight into an application might also need to take into account digital signals from a control system or an automotive bus such as CAN/LIN.
These results then have to be processed, and trend displays produced, which in turn are combined into a single measurement overview, making it possible to find relationships and interactions between different parts of the system acting alongside one another.
For this type of measurement, providing a unique insight into the dynamic behaviour of a system, a relatively new class of portable instrument known as a ScopeCorder, combining the features of an oscilloscope and a data acquisition recorder, provides a convenient solution.
As an oscilloscope, it measures waveforms and captures events, as well as analysing waveform parameters and providing the ability to calculate and trigger on power-related values in real-time. As a data acquisition recorder, it incorporates isolated input channels enabling it to handle a wide range of power measurements, and captures high-resolution details with 12 or 16 bit A/D converters. It also incorporates a large-capacity (up to two gigapoints) memory which will allow it to measure continuously for up to 200 days, while still capturing transient events at data-capture rates of up to 100 MS/s (megasamples per second).
Using flexible modular inputs, the instrument combines measurements of electrical signals, physical signals from sensors and digital signals from CAN/LIN serial buses. Users can choose from 17 input modules to configure a ScopeCorder up to 128 channels, and can gain a thorough insight into any application by synchronising the measurement of different types of electrical and physical signals.
Today, ScopeCorders are widely used in industries such as automotive and aerospace where measurements of physical quantities need to be displayed and analysed alongside electrical signals. Their potential range of applications in power electronics measurements, however, is increased by the availability of an enhanced instrument, the DL850E ScopeCorder (Fig.1), with capabilities for the real-time measurement and analysis of electrical power in addition to the standard set of basic arithmetic mathematical functions and fast Fourier transformation.
With the real-time measurement capability, the instrument can carry out trend calculations such as active power, power factor, integrated power and harmonics, using a dedicated digital signal processor (DSP) that is able to calculate and display up to 126 types of electrical power-related parameters in real time. This enables the user not only to display raw waveform signals such as voltages and currents along with calculated power parameters, but also to trigger on any or all of them. The data updating rate is up to 100 kS/s. Trend waveforms of each order of harmonics, bar-graphs and vector displays can be displayed, and both RMS and power analysis modes are available (Fig.2).
In addition, a vehicle edition of the ScopeCorder (DL850EV) is designed for engineers working in the automotive and railway industries. A common measurement challenge in the automotive sector is to combine measurements of electrical signals, physical performance parameters, indicated by sensors, together with CAN- or LIN-bus data transmitted by the powertrain management system. The ScopeCorder Vehicle Edition addresses this requirement by providing a thorough insight into the dynamic behaviour of the electromechanical system. This saves time compared to other approaches such as analysis on a PC or the use of other software. This unit is also designed for use with vehicle batteries to enable in-vehicle testing.
In industrial welding systems, there is a trend for transformers to be replaced by inverters, and there is a link between the quality of power supplied and the quality of the weld. Hence it is vital to measure inverter efficiency and performance, including harmonics, using a power meter as an aid to quality control.
For industrial welding robots, on the other hand, additional parameters have to be taken into account, including positioning, temperature, and signals from the control system. The ScopeCorder can provide quality assurance by combining electrical, physical and control bus parameters and provide trending and triggering on power values.
The ScopeCorder is an ideal tool for providing a thorough insight into the behaviour of electromechanical systems by linking the cause and effect of interdependent parameters.
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