Test Method: High-Precision Measurement Instruments
The reliability of PSU testing depends on the test setup and the measurement instruments used. Since the significant differences can be small, you need high-precision equipment for them to be documented in a way that's both clear and reproducible.
The cornerstone of all of these measurements is a defined and stable input voltage. Using power straight from the wall socket is out of the question, since this power source is subject to several confounding factors that might lead to significant fluctuations. Instead, we use the high-precision Chroma AC Source 6530, ensuring that all tests are provided with accurate AC voltages of 115V and 230V at a perfect sine curve of 50 or 60 Hz.
We use the precision power meter Yokogawa WT210 for measuring the voltage and current fed by the Chroma. The device attaches directly to the power source and measures voltage, current, power, power factor, and frequency with an accuracy of about 99.9 percent. With a maximum input limit of 26A, it's ideally suited for monitoring the power consumption of high-performance systems.
Clearly-defined DC loads have to be simulated on the different individual rails during all of the measurements. Since this also requires precision instruments, we use a total of eight Chroma DC electronic loads from the 6330-series.
Four of these are capable of generating a maximum load of 600W each to be used as loads for the 12V rails. The remaining four Chroma DC loads (300W maximum each) are responsible for load generation on the 3.3V, 5V, 5V sb, and -12V rails. Three dedicated control units are used for the basic configuration and to recall programmed scenarios. All units come with a feature for generating a controlled short circuit.
We also use a modern oscilloscope, the Tektronix Scope DPO3034, for graphic processing of the measurement results. The four-channel, 300 MHz oscilloscope provides us with readings of voltage, current, frequency, ripple, and rise/fall time. Thanks to its integrated Plug'n'Play PC interface, LAN, and USB connections for external storage, the DPO3034 can be comfortably integrated with the rest of our IT infrastructure.
With the press of a button, a screenshot gets saved as an image file directly to the external storage device connected to the oscilloscope. Not least of all, our Tektronix TCP150 measurement probe is able to handle currents of up to 150A and is an important addition to the oscilloscope for monitoring current flow.