Measuring Ambient Air And Water Temperature
Our setup is designed to keep a record of air and liquid temperatures inside the closed case. While these values aren't tied directly to the hardware we test, they can help interpret results, and are thus an important addition.
Coolant temperature is measured where the warmed fluid flows back to the radiator (as a worst-case scenario), while air temperature is measured where the case gets hottest. Thanks to its fins, the little aluminum sink we're using has lots of surface area and thus adjusts quickly to changes in ambient temperature. I pressed a sensor into the bottom part of the cooler and secured it in place so that there is direct contact between both.
Readings are taken at the front of the system using two digital displays. This makes it easy to put the measured values into context, as the Gigabyte GTX 1070 G1 Gaming example below illustrates well.
|Metro Last Light Open Test Bench||87°F (30.6°C)||82.9°F (28.3°C)||147.2°F (64°C)||47.28|
|Metro Last Light Closed Test Bench||89.4°F (31.9°C)||106.2°F (41.2°C)||150.8 °F (66°C)||47.15|
|FurMark Open Test Bench||84.9°F (29.4°C)||79°F (26.1°C)||152.6 °F (67°C)||52|
|FurMark Closed Test Bench||85.6°F (29.8°C)||102.6°F (39.2°C)||156.2 °F (69°C)||51|
These measurements are one part of the story, but they're by no means all of it. We also need to pay some attention to component-level temperatures, which are sometimes conveyed as VRM or VRM1/VRM2 in tools like GPU-Z. Except that those readings are wrong! They're representative of the PWM controllers, which aren't even close, physically, to the VRMs.
In order to actually record those temperatures, you have to do it directly. This is exactly why you see us use Optris' PI640 thermal camera. For more information on how we use this device, check out Measurement Science: Taking Accurate IR Thermal Readings.
PCs contain a number of objects that radiate heat, from liquid cooling pipes to memory modules, storage devices, and host processors. Because we don't want them in our infrared images, we test graphics boards on a riser card that puts additional distance between the motherboard.
When we do this correctly, it's possible to almost perfectly measure just the card's thermal energy in a closed case.
To this day, we haven't seen anyone else able to take such accurate measurements, if only because there aren't any usable test systems available. The difference between Gigabyte's GTX 1070 G1 Gaming operating in open and closed cases is clearly visible:
Our measurements reveal a difference of about two Kelvin, which we already observed in the closed reference case. Of course, that number can climb even higher depending on the system configuration and cooling solution.
Fan speed is influenced by higher temperatures, of course, resulting in more noise when we test graphics cards the way you actually use them.
|Measurement Technology||Thermal imaging technology: Optris PI640 infrared camera PI Connect analysis software with profilesSensors: Modified temperature sensor with large aluminum block|
|Measurement Method||Infrared monitoring in real-time Video and image recording Calibration using a simple infrared calibrator Sensor recording (digital display)|