WT5000 Precision Power Analyzer - New possibilities with raw-waveform data streaming

Recently the award winning WT5000 Precision Power Analyzer received its first major update to its options and functions. This allows the user to capture raw waveform data simultaneously with the numeric measurement data. Both the raw data and numeric data can be sent directly to the test bench software.    

Raw data are the individual sampling points of the A/D converter. Using the WT5000 precision power analyzer and the new /DS option, these sampling points can now record  the voltage and current input signals as well as the analog torque, speed and auxiliary signals.  
Depending on the number of traces that the application requires to be stored, these can be streamed with sampling rates of up to 2 MS/s to a computer or directly into an evaluation system. The data is transmitted continuously and seamlessly, synchronized to the numerical data. Recording only stops when the bench computer’s memory is full.

For the user, the raw data streaming option offers the following three main advantages:

1.    Saves expensive test bench time 

Engineers who work on test benches know that test bench time is expensive. With the raw data streaming option, the user can now perform all analyses offline after measurements have been taken. Interesting parameters that were not recorded or calculated during the measurement done at the test bench can now be determined offline via software packages, such as Matlab, from the streamed and recorded raw  data.  This way of determining parameters saves not only working time, for example, for re-connecting the device under test, but also the availability of the test bench to perform other measurements. As a result, the /DS option gives the user a significant time advantage, as well as  more flexibility and economic benefits. 

2.    Time-synchronous recording of numeric and raw data

Another advantage is that the raw data is recorded simultaneously and in parallel with the highly accurate numerical measurement results of the WT5000. Abnormalities in the numerical measurements can now be compared directly with the waveform data, allowing their causes to be investigated and understood more quickly.  

3.    Recording transient operations

Precision power analyzers offer the best performance for static operating points, as calculation of the uncertainty of measurements needs to include the standard deviation between multiple samples, the smallest under stable conditions. The new raw data streaming option of the WT5000 adds an additional layer of flexibility, allowing the study and evaluation  of transient behavior, 
for example, the start-up or braking processes of electric motors.

Configurating the raw data option

However, before the first raw data is streamed and the user can start using it, we can set application-specific parameters for the transmission of the raw data to the test bench computer. The WT5000 offers several settings for this.

The sampling rate at which the WT5000 continuously outputs the raw data during the measurement can be freely selected from the following eight levels:
10 k, 20 k, 50 k, 100 k, 200 k, 500 k, 1 M and 2 MS/s.

This means that the user can set the sampling rate that is most suitable for their application. It is also possible to select from which inputs the waveform traces need to be streamed to the computer,   so that only the data of the selected voltage, current,  and torque/speed or auxiliary signals are streamed.  

Both of these configuration options are particularly advantageous because of the sometimes large amounts of data that can be generated by the raw data streaming option, especially as such measurement files usually need to be stored for a longer time.  

Regardless of the setting of the sampling rate for raw data streaming, the WT5000 continues to sample both the voltage and current signals for all seven power measurement channels with the fixed and non-changing sampling rate of 10 MS/s via the 18-bit A/D converters. The numerical measurement results, that the WT5000 determines with the highest precision in the world, are based on the 10 MS/s sample speed. For raw data streaming, the WT5000 reduces the 10 MS/s and streams according to the selected sampling rate of the /DS option.  For example, if the sampling rate of 2 MS/s is set for raw data streaming, every fifth sample value of the A/D converter is transmitted.

Raw data streaming via Gigabit Ethernet and USB 3.0

The high sample rate of up to 2 MS/s, which the WT5000 provides continuously and seamlessly, is achieved via communication interfaces, Gigabit Ethernet or USB 3.0. Not to be forgotten are the numerical measurement data as well as the peak-to-peak compressed waveform display data, which can be transmitted in parallel and time synchronously to the raw data when required. In terms of numbers, this means that for raw data streaming of an electrical power measurement signal, i.e.  for sampling values of one voltage trace and one current trace with 2 MS/s, the data rate will be 960 MB of data per minute. In one hour, these add up to 57.6 GB. 

Of course, the test bench computer must be able to receive, process and store these data packages. In an Ethernet network, in which several subscribers receive and send files at the same time, the continuous and seamless streaming of these data messages is a point of consideration. This is also the background of the  different maximum number of traces  that can be used via the USB 3.0 and Gigabit Ethernet for the different sample rates.

Table 1 provides information about the number of wave forms (Waveform Trace Count), which can be streamed simultaneously from the WT5000 depending on the interface and sampling rate used.
 

Open commands for maximum flexibility 

Typical for Yokogawa power analyzers are the open commands for controlling the devices. The commands for raw data streaming are also published, and enable users to stream all raw data directly into their software.  

Because the commands are already published, the WT5000 can be fully configured and operated. A  user can expand their own pre-programmed measuring software relatively easily to adapt the raw data streaming option. This is particularly interesting for test bench manufacturers who work with their own software, but also for every user who wants to integrate the data into his system.

An excellent alternative is Yokogawa's WTViewerE software. With this, the WT5000 can be used not only to parameterize and control, but also to record the raw data. 

The first signal analyses can already be carried out in the WTViewerE via the analytical function (see Fig.1), while  the comparison with the numeric measurement data can be carried out very easily. Subsequently, depending on the setting, only the analyzed section of the measurement or the complete measurement can be converted and output as a CSV file. The user enjoys maximum flexibility and can continue to use the measurement data as desired.  

In summary, the WT5000 precision power analyzer, in combination with the raw data streaming option, now offers the user more flexibility and a wide range of possibilities for analyzing the measurement data.