Memory card temperature and radiation test (ATP 4Gb SDHC Class 6)

Nowadays, testing memory cards with just the camera and the card reader is a bit passé. Most modern memory cards are fast enough for shooting in normal conditions. During the testing of the currently fastest card, the SanDisk Extreme IV, we saw how quick the card is when it comes to reading and writing and where such speed could come in handy.

At Photokina 2006, the SanDisk rep hinted that the Extreme IV was introduced to work with the newest Canon camera. This was the recently unveiled EOS 1D Mk III, which is capable of using SDHC cards. SD card vendors reacted by introducing new SDHC cards, which offer higher capacity and higher speeds. They also adopted a new standard of speed classification, designating cards into separate classes. This particular card is Class 6, which in layman’s terms means that they have a sustained 6MB/s rate of transfer. The first camera in which the card could be tested was the Nikon D80. I personally tested it with the Pentax K10D. But such tests don't really tell much.

It takes time to really get to know a card and its faults, and of course one should also test the competition. As to the transfer rates, well, there's always the choice between trusting the manufacturer or testing them personally. However, testing such cards to their limits is often difficult.

ATP, a company which was up to now primarily known for their high quality industrial cards, sent us one of their best products, the SDHC Class 6 SD card. As mentioned before, I tested it with the Pentax K10D, but I also tested it with the supplied USB 2.0 card reader on both Windows and Mac PCs. Again, this proved that the card is very quick and that ATP is, as usual, at the cutting edge.

However, I like to go beyond the current norm - check the specs, add in a few manufacturer-supplied lines and test the card briefly with a camera and a computer. I like practical tests. This is even more true when a company provides a product designed for extreme conditions. In 2001, I simply tossed the EOS 1D into the snow and then left in the sun, waiting for the snow on it to melt. Well, they claimed that it was weatherproof, didn't they? It worked perfectly. Of course there are certain boundaries one cannot step over, but sometimes, you just have to trust the engineers who designed the stuff.

Up to now, I had very few problems with cards, even in extreme conditions. Which made it difficult to think of a way of testing the card beyond what is usual.

Environment specification

Then, the idea came flying through the window on a flaming pie. Memory cards are not just used in photography, they also have industrial applications. And believe it or not, photography is not a very demanding application for such a card. Put these cards into a production environment, let alone a military or spaceflight environment, and you’re facing a completely different set of conditions. This is not your garden-or-common operating environment, this is an environment in which high temperatures, humidity and vibrations are commonplace.

Oddly (and luckily) enough, the editor of the Croatian version of e-Fotografija works at a nuclear plant. In some of the more exposed locations, they use automated equipment to record data on CF and SD cards. This rough environment seemed perfect for testing the ATP card.

We then decided that that wasn’t quite it. We could add another variable – radiation. With all the traveling these days and increased security checks at the airports, X-ray exposure is a fact of life. Film was never entirely safe, especially when passing through multiple airports. So, what would happen with a memory card? Read on and find out.

Digital photography has replaced a film with the combination of a CCD/CMOS sensor and memory cards. Film was both a sensor and memory card at the same time. With the advent of digital technology, it got separated in two components. The CCD/CMOS sensor we use is determined by the camera we use, while memory cards are bought separately. In normal conditions we don’t think about how reliable memory cards are for storing pictures. They’re well proven. It’s the extreme conditions that worry us. Temperature, humidity and dust. All these can affect reliability of keeping our pictures safe on electronic media such as memory cards. In the mountains, at low temperatures, or at the beach in the middle of summer, our equipment can be exposed to the temperatures which are outside recommended operating conditions.

At the start of the production of electronic components, operating temperature range was divided in three categories. Commercial, industrial, military. After a while, an extended (industrial) range was added. Now, there are four temperature ranges for components. These ranges are:

Commercial: 0°C – +70°C

Industrial: -40°C – +85°C

Extended: -40°C – +125°C

Military: -55°C – +125°C

The technology of component production, especially silicon components such as chips, is the same for all temperature ranges. Testing in production determines the operating temperature range and the components are then packaged in suitable casing for the temperature range. Mass production made individual testing of each part impossible, therefore sample testing of each series was introduced. Because of this, it's possible to find an above average part in lower speeced components and vice versa, a bad part in high–specced components.

When talking about memory cards as components, one somewhat neglected parameter has a profound effect on data reliability and the durability of card. This is the number of times the card can be inserted, which depends on gold thickness on contacts.