From the working principle, there are two types of glucometers, one is photoelectric and the other is electrode. The photoelectric glucometer is similar to a CD player, with a photoelectric head. Its advantage is that it is relatively inexpensive, but the disadvantage is that the detection head is exposed to the air, making it very susceptible to contamination, which can affect the test results. The error range is about ±0.8, and its service life is relatively short. It is generally accurate within two years, and after two years, it is recommended that patients using photoelectric machines go to a maintenance station for calibration.