Power analysis without disruption - five in one

In a typical test scenario, the way from raw signals to the final pass/fail indication is a long and winding path stretching over five distinct phases. Computing RMS pow­er is only one piece of the puzzle, and data from other sources might need to be inte­grated into the calculations. This can lead to a complex assortment of data sources and processing tools with many handover points. The discontinuities in the flow of data may require manual intervention, which demands time and effort and in­creases the risk of introducing errors.

The power analyzer LMG671 is designed to combine all five phases of testing into a single instrument, thus eliminating unnecessary complexity, streamlining the testing process, making test engineers’ life easier and keeping cost down.

3d graph drive train

1. Signal acquisition: the LMG671 goes beyond voltage and power. The versatile Process Signal Interface (PSI) can read virtually any analog or digital signal source, thus allowing e.g. temperature, pressure, speed, torque and other data to be collected together with voltage and current. No need to reconcile data points from different sources later on, no issues with inconsistent timestamps between variables.

2. Timing control: for the test results to be meaningful, the DUT needs to be ob­served in specific, predefined modes of operation. The LMG671 can control begin­ning and end of the measurements via the versatile Event Trigger option. In addi­tion, it can react to external trigger inputs or CAN bus commands to start recording data. The LMG671 can also control exter­nal devices via a number of analog and digital outputs in the optional PSI.

3. Integration: to calculate RMS voltage, current and power as well as harmonic values, the samples need to be summed over entire signal periods – this is the traditional domain of power analysis. (Outsourcing the calculation to PC envi­ronments already at this step renders the integrity of RMS values and harmonics vul­nerable and makes calibration of the setup rather difficult.)

4. Derivation: in many applications, the measurement of electrical quantities is just a means to an end and not the final goal. An illustrative example is the qualification of inductive components: measuring volt­age and current ultimately yields core loss­es and the peak values of magnetic field strength and flux density. Rather than ex­porting electric measurements to 3rd party applications for the calculation of the de­sired results, the LMG671 offers a powerful built-in programming language with a vast number of mathematical functions to car­ry out all required calculations in one fell swoop. No handover, no disruptions, no risk of additional errors.

5. Pass/fail decision: In case the DUT is tested against defined standards or previously established benchmarks, the pass/fail limits can be programmed into the LMG671 in order to allow the instru­ment to display the outcome of the test directly. Should there be different pass/ fail criteria for consecutive DUTs, applica­ble limits can even be adjusted on-screen by the test engineer use the touchscreen GUI’s input boxes or arrow keys. Some tests require additional information (like e.g. magnetic path length, core diameter etc.) on the DUT that varies between tests and also needs to be considered for calculation. Also this kind of data can be entered and changed directly on-screen using a number of available input elements. These built-in decision-support features allow even less experienced or less well-trained users to reliably judge success or failure of the test.