Why you can trust Tom's Hardware Our expert reviewers spend hours testing and comparing products and services so you can choose the best for you. Find out more about how we test.
Transient Response Tests, Ripple Measurements and EMC Pre-Compliance Testing
Advanced Transient Response Tests
For details about our transient response testing, please click here.
In the real world, power supplies are always working with loads that change. It's of immense importance, then, for the PSU to keep its rails within the ATX specification's defined ranges. The smaller the deviations, the more stable your PC will be with less stress applied to its components.
We should note that the ATX spec requires capacitive loading during the transient rests, but in our methodology, we also choose to apply a worst case scenario with no extra capacitance on the rails.
Advanced Transient Response at 20% – 200ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.090V | 11.963V | 1.05% | Pass |
| 5V | 5.039V | 4.954V | 1.69% | Pass |
| 3.3V | 3.311V | 3.166V | 4.38% | Pass |
| 5VSB | 5.018V | 4.964V | 1.08% | Pass |
Advanced Transient Response at 20% – 20ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.090V | 11.924V | 1.37% | Pass |
| 5V | 5.039V | 4.941V | 1.94% | Pass |
| 3.3V | 3.311V | 3.133V | 5.38% | Fail |
| 5VSB | 5.018V | 4.958V | 1.20% | Pass |
Advanced Transient Response at 20% – 1ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.088V | 11.902V | 1.54% | Pass |
| 5V | 5.039V | 4.941V | 1.94% | Pass |
| 3.3V | 3.311V | 3.138V | 5.23% | Fail |
| 5VSB | 5.018V | 4.901V | 2.33% | Pass |
Advanced Transient Response at 50% – 200ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.043V | 11.963V | 0.66% | Pass |
| 5V | 5.026V | 4.936V | 1.79% | Pass |
| 3.3V | 3.305V | 3.152V | 4.63% | Pass |
| 5VSB | 4.996V | 4.939V | 1.14% | Pass |
Advanced Transient Response at 50% – 20ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.043V | 11.931V | 0.93% | Pass |
| 5V | 5.026V | 4.925V | 2.01% | Pass |
| 3.3V | 3.305V | 3.120V | 5.60% | Fail |
| 5VSB | 4.996V | 4.920V | 1.52% | Pass |
Advanced Transient Response at 50% – 1ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.041V | 11.943V | 0.81% | Pass |
| 5V | 5.026V | 4.918V | 2.15% | Pass |
| 3.3V | 3.305V | 3.119V | 5.63% | Fail |
| 5VSB | 4.996V | 4.927V | 1.38% | Pass |
The transient response of the +12V rail is satisfactory and the same applies to the 5V and 5VSB rails. On the contrary, there is (a lot of) room for improvement on the 3.3V rail, which failed in most tests.
Turn-On Transient Tests
In the next set of tests, we measure the PSU's response in simpler transient load scenarios—during its power-on phase. Ideally, we don't want to see any voltage overshoots or spikes since those put a lot of stress on the DC-DC converters of installed components.
Comments
Ripple Measurements
Ripple represents the AC fluctuations (periodic) and noise (random) found in the PSU's DC rails. This phenomenon significantly decreases the capacitors' lifespan because it causes them to run hotter. A 10-degree Celsius increase can cut into a cap's useful life by 50%. Ripple also plays an important role in overall system stability, especially when overclocking is involved.
The ripple limits, according to the ATX specification, are 120mV (+12V) and 50mV (5V, 3.3V, and 5VSB).
| Test | 12V | 5V | 3.3V | 5VSB | Pass/Fail |
|---|---|---|---|---|---|
| 10% Load | 4.9 mV | 6.4 mV | 9.1 mV | 7.2 mV | Pass |
| 20% Load | 10.6 mV | 7.2 mV | 11.2 mV | 8.2 mV | Pass |
| 30% Load | 7.6 mV | 8.1 mV | 11.3 mV | 8.3 mV | Pass |
| 40% Load | 9.3 mV | 9.4 mV | 11.6 mV | 8.4 mV | Pass |
| 50% Load | 9.1 mV | 9.3 mV | 11.6 mV | 8.0 mV | Pass |
| 60% Load | 9.6 mV | 10.4 mV | 13.2 mV | 8.4 mV | Pass |
| 70% Load | 10.6 mV | 11.2 mV | 13.9 mV | 8.5 mV | Pass |
| 80% Load | 11.7 mV | 11.6 mV | 15.1 mV | 9.3 mV | Pass |
| 90% Load | 12.5 mV | 12.5 mV | 16.6 mV | 8.7 mV | Pass |
| 100% Load | 16.8 mV | 14.8 mV | 16.6 mV | 11.0 mV | Pass |
| 110% Load | 17.8 mV | 14.5 mV | 18.6 mV | 11.0 mV | Pass |
| Crossload 1 | 18.8 mV | 10.7 mV | 16.6 mV | 8.9 mV | Pass |
| Crossload 2 | 17.8 mV | 11.4 mV | 15.5 mV | 10.2 mV | Pass |
The ripple suppression might not be at the perfect levels that the RM850x achieves, because the RM850's modular cables don't use any in-cable caps, but still is very good
Ripple At Full Load
Ripple At 110% Load
Ripple At Cross-Load 1
Ripple At Cross-Load 2
EMC Pre-Compliance Testing – Average & Peak EMI Detector Results
Electromagnetic Compatibility (EMC) is the ability of a device to operate properly in its environment without disrupting the proper operation of other close-by devices.
Electromagnetic Interference (EMI) stands for the electromagnetic energy a device emits, and it can cause problems in other close-by devices if too high. For example, it can be the cause of increased static noise in your headphones or/and speakers.
The conducted EMI emissions are low, throughout the entire frequency range that we measured (150KHz - 30MHz).
MORE: Best Power Supplies
MORE: How We Test Power Supplies
MORE: All Power Supply Content
EKWB reportedly plagued with financial disarray — many employees and suppliers were allegedly left unpaid for as long as four months
Adding ZIP file support to Windows 30 years ago almost got the creator of Task Manager fired
Carry-on server flexes up to 256 cores — 480TB NVMe and 4TB RAM join Ampere Altra CPU in new fly-away-kits
