Precision is Key to Today's Power Measurements




Power design is more complex than it has even been, and that trend is set to accelerate due to many factors. At board level, shrinking IC geometries demand higher currents in smaller spaces, as well as very precise slew rates and boot up sequences. At the higher power end of the scale, alternative energy sources and electric vehicles are designed to extract every available joule of energy from the source. There is also a rise in the demand for complex electromechanical products, such as robotics, which demand precise voltages applied with strict timing limitations. As if those demands weren’t enough, designers also must tread a narrow path between getting the best design possible and complying with a slew of regulations on efficiency, interoperability and safety.

To meet all of these demands requires a comprehensive testing methodology, and reliable and precise equipment. Precision especially is in demand as a few millivolts or milliseconds either way could reduce battery life significantly over time, fail to meet strict limits laid down in legislation or cause a nasty intermittent fault as a vital component fails to start up correctly. The number and variety of different tests that need to be performed can often require a full benchtop of instrumentation.

Yokogawa has looked at the problems facing power designers and developed a solution that offers both high precision measurement, and a flexible modular approach which allows developers to create a bespoke instrument for each test. The Yokogawa WT5000 features an accuracy of ±0.03% at 50/60 Hz along with high levels of stability and noise immunity, allowing the easy and accurate measurement of power consumption, loss, and efficiency for the device under test.

At the heart of the instrument is an 18-bit analog to digital converter with a sampling rate of 10MS/s, which allows the device to accurately capture waveforms and provide stable measurements from the seven input channels. In the past, capturing seven separate inputs would require several instruments to be linked and synchronized.

The seven inputs are designed to make multi-system measurements easier to perform. For example, the WT5000 can carry out two harmonic measurement functions simultaneously, each at up the 500th order and up to 300kHz fundamental waveform. This makes it possible to measure the carrier frequency from the rotational speed of a motor in the inverter drive and also to check the influence of the carrier frequency on the motor drive.

The modular design of the WT5000 allows elements to be switched out depending on the requirements of the desired test. For example, the 30 A and 5 A elements can be switched to allow developers to evaluate a number of different motors.

For larger current measurements, an external current sensor input function is fitted as standard in the input element of both the 30 A and 5 A input elements of the WT5000. For even larger currents of up to 2,000 A rms, a measurements can be taken using a dedicated high-current sensors can be used.