Friday, October 30, 2015

New data logger solves the mystery of inconsistent efficiency readings

(Today’s post was written by another one of our experienced engineers, Bill Griffith. Thanks, Bill, for sharing your knowledge and this new feature with everyone!)

While measuring the efficiency of a small 12 Vdc to 115 Vac power inverter the readings fluctuated between 87.80 % and 88.70 % with a consistent load. To learn more about the efficiency, an IntegraVision Power Analyzer with its new data logging feature was used to capture efficiency over time.

The new data logger feature captures every numerical measurement from each channel over a period of time. With just two parameters to configure, the data logger is easy to use. The length of data logging can be as short as 1 second or as long as 365 days. The interval for recording data can be set as low as 50 ms to as high as 24 hours. If an interval of 200 ms or longer is selected, THD and efficiency measurements are also saved. All measurements are gapless, continuous whole cycle measurements.

Below is a graph of efficiency. As you can see the efficiency changes over time.

Efficiency is calculated from the output power divided by the input power. The data logger file contains the output and input power. Both are graphed below.

We can see the efficiency is fluctuating due to the input power. The inverter contains a small fan that turns on about every 10 seconds and increases the amount of power required.

If you are interested in seeing a video of the inverter being tested, watch this YouTube video.

A couple of final notes on using the data logger: the data logger file is a csv file; the rows are time stamped and hold the measurements for each interval. Each column is for a different measurement and a single channel can have over 30 measurements. The columns are labeled for each type of measurement and by channel. Check out the video mentioned above to see the data logger file and all of this in action.