Digital pregnancy tests have an internal paper test
I'm not too sure why this is supposed to be surprising. When chemical reactions are involved, you often need chemicals.A significant portion of digital meters used for servicing swimming pools require servicing/replacement of strips/chemicals (reagents) within the device.Yes, there are also digital meters that work without chemicals per se, and have special electrodes that measure electric current. However, this approach quite simply doesn't work for all chemical reactions.