Precision Making

Auto Update Mode of the WT5000 Precision Power Analyzer automatically selects the right measurement interval

by Andreas Maushammer July 6, 2023

As a user of power analyzers, have you ever wished that measurement intervals could be set automatically, without you having to think about it?

There is no longer a need to wish, as the latest update to the firmware of Yokogawa’s WT5000 Precision Power Analyzer provides exactly that.

The Auto Update Mode upgrade ensures that the instrument can select its own measuring interval depending on the applied signal.

For a user, this means that the measuring interval adapts to all frequencies. This makes Auto Update Mode particularly interesting for applications with variable frequencies from 0.1 Hz, for example for efficiency analyses during start-up and braking processes.

By synchronizing to the rotation of a rotor, measurements can be made even more precisely, even at very low motor speeds.

The Auto Update Mode in Detail

Although the WT5000 in Auto Update Mode selects the measuring interval, the user can also set an update rate (10 ms or 50 ms). YOKOGAWA defines the update rate as the time after which a measurement data update is always provided in constant update mode and at the earliest in the auto update mode.

In addition, the measuring interval is an important parameter and depending on the applied signal, because the measuring interval describes the time in which the measurement results are determined or one or more complete periods of the signal to be measured are acquired.

By contrast to the Constant Update Mode (measurement data is always provided after each update rate), in the Auto Update Mode, the WT5000 measures automatically over one or more update rates until at least one complete signal period has been acquired. (see figure 1) The advantage for the user is that one setting fits for all frequencies.

Figure 1: The Auto Update Mode is particularly suitable for applications with variable frequencies, e.g. for a motor start-up. The WT5000 automatically adapts the measuring interval for each period of the applied signal.

To correctly determine the electrical power of the signal which need to be measured, the WT5000 always acquires complete signal periods. This is important because, by definition, the electrical power is determined over one or more complete signal periods.

What does this mean for the user? It means that a new measured value is only output by the WT5000 after at least one complete period has been acquired – at the earliest after the set update rate of 10 ms or 50 ms has elapsed.

Measurement results and time stamp

When saving measurement data while the Auto Update Mode is active, the measured value from the previous signal period is repeated – depending on the set update rate in 10 ms or 50 ms steps – until the current period is completed and a new measured value is available. This is essential because the measurement results from different power modules, the harmonic analysis and the motor options may be available at different times because of independent measurements. Via status information for each element/option in the measurement data, the user is informed as soon as there is a measurement data update available.

This significantly simplifies the evaluation of measurement data for the user.

Another benefit of the Auto Update Mode is that harmonic analyses can also be performed with the 10 ms update rate – in Constant Update Mode, harmonic analyses are only possible with an update rate of 50 ms.

The Auto Update Mode also allows better measurements at very low engine speeds. For this, the Z-signal of the engine can be selected as the synchronization source, with the measurement interval synchronized to the exact duration of a mechanical revolution.

Especially at very low speeds, where the frequencies to be measured are also very small and therefore the synchronization via the electrical measurement is challenging due to the small amplitude, the Auto Update Mode and the synchronization to the rotation of a rotor can be used to achieve even more precise measurement results.

The Yokogawa WT5000 is already highly accurate and with the new Auto Update Mode, it just got even better and more usable.