NZXT E Series 850W PSU Review: An Analog Platform With Digital Enhancements

Transient Response Tests

Advanced Transient Response Tests

For details on our transient response testing, please click here.

Ιn these tests, we monitor the E850's response in several scenarios. First, a transient load (10A at +12V, 5A at 5V, 5A at 3.3V, and 0.5A at 5VSB) is applied for 200ms as the PSU works at 20 percent load. In the second scenario, it's hit by the same transient load while operating at 50 percent load.

In the next sets of tests, we increase the transient load on the major rails with a new configuration: 15A at +12V, 6A at 5V, 6A at 3.3V, and 0.5A at 5VSB. We also increase the load-changing repetition rate from 5 Hz (200ms) to 50 Hz (20ms). Again, this runs with the PSU operating at 20 and 50 percent load.

The last tests are even tougher. Although we keep the same loads, the load-changing repetition rate rises to 1 kHz (1ms).

In all of the tests, we use an oscilloscope to measure the voltage drops caused by the transient load. The voltages should remain within the ATX specification's regulation limits.

These tests are crucial because they simulate the transient loads a PSU is likely to handle (such as booting a RAID array or an instant 100 percent load of CPU/GPUs). We call these "Advanced Transient Response Tests," and they are designed to be very tough to master, especially for a PSU with a capacity of less than 500W.  

We should note that the ATX spec requires for capacitive loading during the transient rests, but in our methodology we chose to apply the worst case scenario with no extra capacitance on the rails. 

Advanced Transient Response at 20 Percent – 200ms

Advanced Transient Response at 20 Percent – 20ms

Advanced Transient Response at 20 Percent – 1ms

Advanced Transient Response at 50 Percent – 200ms

Advanced Transient Response at 50 Percent – 20ms

Advanced Transient Response at 50 Percent – 1ms

Image 1 of 5

NZXT's transient response at +12V is satisfactory. However, Seasonic's SSR-850FX performed notably better.

There is also room for improvement on the 5V and 3.3V rails. At least the 5VSB rail gives us nothing to complain about.

In general, this platform doesn't handle transient loads on the minor rails well, especially at 3.3V. But the E850 does behave better than Seasonic's SSR-850FX on that rail.

Here are the oscilloscope screenshots we took during Advanced Transient Response Testing:

Transient Response At 20 Percent Load – 200ms

Image 1 of 4

Transient Response At 20 Percent Load – 20ms

Image 1 of 4

Transient Response At 20 Percent Load – 1ms

Image 1 of 4

Transient Response At 50 Percent Load – 200ms

Image 1 of 4

Transient Response At 50 Percent Load – 20ms

Image 1 of 4

Transient Response At 50 Percent Load – 1ms

Image 1 of 4

Turn-On Transient Tests

In the next set of tests, we measure the E850’s response in simpler transient load scenarios—during its power-on phase.

For our first measurement, we turn the unit off, dial in the maximum current the 5VSB rail can handle, and switch the PSU back on. During the second test, we dial the maximum load the +12V rail can handle and start the PSU while it is in standby mode. In the last test, while the PSU is completely switched off, we dial the maximum load the +12V rail can handle before restoring power. The ATX specification states that recorded spikes on all rails should not exceed 10 percent of their nominal values (+10 percent for 12V is 13.2V, and 5.5 V for 5V).    

Image 1 of 3

There is a tiny spike at 5VSB, and we notice a couple of small waves in the second test's waveform. In the third test, there are some voltage oscillations that don't look good.

MORE: Best Power Supplies

MORE: How We Test Power Supplies

MORE: All Power Supply Content