DSP Functions Bolster Power Measurement

DSP Functions Bolster Power Measurement

A new real-time mathematics option for the Yokogawa DL850 ScopeCorder introduces DSP-based functions that boost the instrument's power analysis capabilities. It also adds features such as sensor linearisation and electrical-to-mechanical conversion. 

In addition to 30 mathematical functions, the new /G3 option expands the instrument's standard bandwidth filters with a set of steep digital filters for triggering specific measurement sequences based on waveform characteristics. With the /G3 option, the DL850 ScopeCorder offers up to 16 real-time DSP channels and 30 mathematical functions, including calculations of power, sensor linearisation, rotary encoding, and mechanical displacement. The mathematical sampling rate can reach 10Msamples/s, while the filter sample rate runs up to 1 Msamples/s.

The acquisition rate is fast because no processing occurs after waveform acquisition, apart from a fixed calculation delay in the DSP channel. In the real-time mathematical computations on waveform data, the digital signal processor uses the input module’s output data as its source, outputting the computed data to the acquisition memory of the DL850 ScopeCorder.

Using real-time mathematics, input channels can be multiplied, divided, or integrated. Moreover, dedicated functions such as power integration, three-phase real power measurements, and differentiation can be carried out. The /G3 option also makes it possible to set trigger conditions based on DSP or digital-filter function results.

Typical applications include using the RMS mathematical operator to trend the RMS value of each voltage or current waveform’s individual cycle, or using the (S1 x S2) operator to multiply the voltage and current waveforms to trend the instantaneous power waveform. To determine a system’s power usage, a power integration function will trend the integrated power over time in watt-hours or watt-seconds.

A mechanical versus electrical phase function calculates the angle between the mechanical rotation measured precisely by a rotary encoder and the input current waveform. This current is often distorted with harmonics. However, the DSP can extract the fundamental component of the current using a discrete Fourier transform to produce a trend of the phase difference for display in real time. 

The DL850 ScopeCorder is a portable instrument that combines the benefits of a high-speed oscilloscope and those of a traditional data-acquisition recorder. Because of its large acquisition memory, it can capture and analyse both long-term trends over measurement periods of up to 30 days and transient events with sample rates up to 100Msamples/s.

Thanks to the range of available input modules, up to 128 channels can be configured with built-in isolation and signal conditioning to capture voltages and currents as well as physical parameters like temperature, stress, and vibration. Using input scaling, all types of physical sensors with voltage output are able to be connected. 

The DL850 ScopeCorder will capture signals coming from power converters, power electronics, and control signals and combine them into a single measurement file.


TAGS: Components
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