Home / Apple / Michael Tsai – Blog – Inside digital pregnancy tests

Michael Tsai – Blog – Inside digital pregnancy tests



Tom Warren (Hacker News):

Pregnancy tests used to be pretty simple sticks you peed on, but the transition to digital versions has turned them into small computers almost as powerful as the original IBM PC. Fascinated by the digital age of pregnancy testing, Twitter users phone and xtoff recently drew examples from Walmart and Clearblue to reveal what’s really going on inside.

Each test, which costs less than $ 5, includes a processor, RAM, a button cell battery and a small LCD screen to display the result.

[…]

You may assume that the addition of an LCD monitor and processor to digitize this pregnancy test improves accuracy or modernizes how the test works, but this is certainly not the case. This digital pregnancy test still contains a strip of paper to measure the chemical reaction you create when urinating on the strip.

This is an interesting user interface problem. Although the paper strip is the same, the digital tester is probably more accurate because it has been calibrated based on actual strips, while the human reads the instructions on the box and may not have seen a number of actual positive and negative results. The digital test is also less stressful because it gives a definite result without having to wonder if you read it properly. How weak a line is too weak to count? Is it just an evaporation line?

The disadvantages are that the digital test for single use is more wasteful, and that the binary result is not 1

00% definitely. In rare situations, it may report a false negative instead of a weak positive. With the analog test, the weak positive will be a sign that you should test again later, or that the hormone levels were off for some reason that may justify investigation.

Design environment

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