Track and field timing systems
Meets use fully automatic timing: a start signal wired to a photo-finish camera. For training, coaches use gates, chips, apps or wearables, which cost a fraction as much and aren't FAT. The two kinds of time don't line up, so you need to know which one you're looking at.
What FAT means
A fully automatic timing (FAT) system starts the clock from the start device itself, usually the gun or a silent electronic starter, and takes the finish from a photo-finish image, read at the moment the torso reaches the line. Since 1977, the IAAF, now World Athletics, has required FAT for sprint world records, and the NFHS requires it for high school national records. FAT times are recorded to the hundredth.
FinishLynx, a common meet system, sells a scholastic package for under $5,700 and full systems for up to about $20,000.
Hand times and the 0.24 s rule
A person with a stopwatch starts late, because they react to the smoke or the sound, and stops early, because they anticipate the finish. So hand times come out faster, and the NFHS has coaches round a hand time up to the next tenth and add 0.24 s to estimate FAT, for seeding only. Track statisticians use the same 0.24 s for 100 and 200 m.
Training timers aren't FAT
Gates, chips and wearables start the clock on your first movement or on a beam you break, and stop when a beam or a sensor crosses a line. None of that matches a gun start and a torso on a photo-finish frame, so their times aren't comparable to meet times without a correction. For training that's fine. You need the same setup to give you the same number from week to week, so you can see whether you're getting faster.
A training timer for sprinters
Sprintbrick times straight sprints out to about 80 m with a sensor on your lower back and one receiver behind the start. The app shows splits every 10 m, your top speed and your fastest flying 10, 20 and 30 m, so a single rep tells you how your acceleration and top speed compare to last week. In our tests against OVR gates, all 30 segments after the first 10 m came within 50 ms. It doesn't time bends, so 200 and 400 m runners can use it for straight-line work only.