A system’s operating temperature looks like a simple range of temperatures. However, a better description is a 3D game of chess. The components (their operating temperatures and thermal limits), the ambient temperature in the environment and the system utilization all come together to give a system a rating. This rating is the key to knowing if your computer can take the heat common in industrial & manufacturing environments. The wrong 30°C PC in a 40°C environment can spell disaster: unintended shutdown, data loss, WiFi failure and more can all happen thanks to temperature. So how do you insulate yourself from failures due to heat? Read on.
Selecting a PC: It’s about the Parts . . . Sort of
Each major component in a PC has its own operating temperature. So to get a system capable of withstanding 60C heat, you need only select systems with parts with specs above 60C, right? Not exactly. Operating temperature represents the operating limits of the part and physical temperature at which the component will fail. Each component will have a range, like the wide temperature drive’s -40°C to 85°C. But components such as RAM, hard drive, WiFi, and processor don’t run in isolation, and they all generate heat. They warm the air around them, and pretty soon a room that is 30°C has parts operating in a 60°C environment. Anyone who has put their hand on the side of a PC case will tell you that they can get pretty warm.
The Case Makes the Difference
Given that components work in an enclosed area, the most important item when it comes to helping determine the rating is the case. The design of a case determines the amount of air flow, the proximity of mounted components, the deployment of heat distribution systems — like heat pipes, heat sinks or fans, and much more. As the components begin to heat up, the case can be the differentiator. A good case will pull heat away from the components. A bad one is an oven in its own right.
System Operating Temperature Determination, Part 1:
To get to the computer’s operating temperature, first you need a baseline. To establish a baseline, thermal performance of a PC is assessed at room temperature (20-21°C). Every computer manufacturer worth its salt has a testing process they run machines through. The tests are proprietary and confidential, but all tend to do the same thing: engage the system’s resources to various degrees, while recording the temperatures of the components.
Using this data, the laws of thermodynamics, and some complicated math, they can extrapolate temperatures above and below room temperature and estimate the temperature point where the various components will reach their fail points. This gives the system a preliminary operating temperature, and is often used to quickly assess a configuration.
Case Study – The ML300: The ML300 series are Fanless Ventless computers from OnLogic. We sent one to Intel for Thermal Testing, which uses a 100% utilization. The thermal limits on components are:
- Processor: 105°C,
- WiFi: 80°C,
- Hard drive (a SSD): 80°C
- Memory: 85°C
Intel tested it, and verified the system for 50°C, which was the highest the ambient temperature could be before one of those parts ticked over its limit. Interestingly at 55°C the WiFi was going strong, but was reading over 80°C and the other parts were still below their limits.
This is both a good example of good case design, with well placed heat sinks (the ML300 series’ case is one big heat sink), but also a good example of the intricacies of testing. The ML300 unit still works at 55°C. If that usage is dialed back to normal, what does the operating temperature look like? It’s hard to say because that’s not part of the test.
System Operating Temperature Determination, Part 2:
The next level of thermal testing involves a Thermal Shock Chamber. These are basically one part oven, one part freezer. The PC is turned on, set to run at a set rate and is heated up to a specific temperature. Components are monitored as their operating temperatures tick up. For example, a WiFi card in a room that’s 20°C (Room temp) might register as operating at 50°C. When the ambient temperature rises to 40°C, that WiFi will be correspondingly hotter. The process repeats with incrementally higher and higher temperatures.
The shock comes in when it is rapidly cooled, usually with liquid nitrogen, from a target temperature. As the temperature drops, it’s doing two things. It is seeing if the rapid shift causes failure. It is also testing how well the various parts function at low temperatures. For example at 0°C.
Then they begin cranking it back up again and the whole process is repeated several times. How and when parts fail is recorded and the result is that system’s operating temperature.
And all this means what?
One of the problems with operating temperature, and testing, is the lack of standardization. Some manufacturers use full utilization, which is to say push a computer to its maximum. Optimal utilization is used by others – an ill defined estimate of standard usage levels. Some utilize a Thermal Shock Chamber and some do not. The variations go on and on, and are not always meant to be confusing or misleading, they are just all proprietary methods and thus hard to judge against each other. A PC might reach 50°C in one test and 40°C in another, only because the one tester uses software to test the temperature, and the other uses sensors on the components.
You will want to look carefully at the system rating, the case design, the wide-temp component options, the enclosure (kiosk, cabinet, etc), the software application and its resource draw, and the ambient environment. If you have an application using relatively few system resources, a 50C rated computer for a factory that never gets hotter than 50C may be OK. But if there is a big system load or local thermal increases due to an enclosure or poor ventilation, you may need more wiggle room. Don’t be afraid to ask your vendor how they verified their numbers.
Want to learn more about the system operation temperature testing of OnLogic computers? Contact our sales engineering team. We’ll work with you to meet your operating temperature specifications.
Note: This blog was originally posted on October 13, 2013. Updates were made for content on March 13, 2021.