We can all agree that pregnancy tests are incredibly useful, regardless of how you choose to handle a pregnancy. The earlier you are able to determine that you’re pregnant, the earlier you can get to a doctor to start taking whatever actions you decide on. At-home pregnancy tests detect hCG (human chorionic gonadotropin), which usually indicates that a woman is pregnant. For most people, hCG will be present in urine within one week after the first day of a missed period. But have you ever wondered how digital pregnancy tests detect hCG? Foone has an in-depth teardown to answer that question.
The typical “analog” pregnancy tests that you can purchase for just a couple of dollars work in a way similar to chemical test strips, such as those to detect chlorine or drugs. Usually, two lines can appear on the indicator portion of the pregnancy test. One line confirms that you have, indeed, peed on the strip. The second line indicates that hCG is present — signaling that you’re probably pregnant. That begs the question: are digital tests any more accurate than their analog cousins? Foone tore apart a digital pregnancy test to find out. As it turns out, the “digital” portion of the test device is little more than a gimmick.
Cracking open the digital pregnancy test yields the most glaring proof of this ruse: a conventional paper test strip. That works in exactly the same way as a typical analog pregnancy test. All of those fancy electronics in the device are there to do only two things: detect the lines on the test strip and show the words “pregnant” or “not pregnant” in LCD clarity. LEDs and photosensors are used to determine if the lines are present on the strip. A Holtek HT48C06 8-bit microcontroller controls those and the LCD. Simply put, all it does is read the lines for you, meaning there is no reason to spend more money for the digital version of a pregnancy test. The only reason the digital versions even exist is for marketing purposes. They capitalize on our tendency to think of digital instruments as being more accurate than analog instruments. In this case, however, that simply isn’t true.
[h/t: The Verge]