Real-time mathematics option boosts power measurements

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

In addition to 30 powerful mathematical functions, the new /G3 option expands the instrument's standard bandwidth filters with a set of steep digital filters that can be used 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 is up to 10 MS/s (megasamples per second), while the filter sample rate is up to 1 MS/s. The fast acquisition rate results from the fact that there is no processing 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 output data of the input module as its source and outputs the computed data to the acquisition memory of the DL850 ScopeCorder. Using real-time mathematics, input channels can be multiplied, divided or integrated, and dedicated functions such as power integration, 3-phase real power measurements and differentiation can be carried out. What makes the /G3 option extra powerful is that the trigger conditions can be set depending on the result of the DSP or digital filter functions.

Typical applications include using the RMS mathematical operator to trend the RMS value of each individual cycle of a voltage or current waveform, or using the (S1 x S2) operator to multiply the voltage and current waveforms in order to trend the instantaneous power waveform.
To determine the power usage of a system, 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, but 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 is able to capture and analyse both long term trends over measurement periods of up to 30 days and transient events with sample rates up to 100 MS/s. The range of input modules available allows the DL850 to be configured up to 128 channels 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 can be connected.

The DL850 ScopeCorder is the ideal tool to capture signals coming from power converters, power electronics and control signals and combine these electrical and physical signals in a single measurement file.