What are the four unreadable instruments in physics

Instruments that do not need to be evaluated: vernier caliper, stopwatch, resistance box, ohm meter (multi-meter ohm file). High school physics readings need to be estimated as follows: 1. Scale, which needs to be accurate to two decimal places. 2. The spiral micrometer, its reading should be in millimeters, should be retained to 3 decimal places, so the spiral micrometer is also called the micrometer. If it's in centimeters it should be kept to four decimal places. 3. The dynamometer needs to be accurate to one decimal place. Ammeter, voltmeter, generally accurate to two decimal places. Pallet scales need to be accurate to one decimal place. Thermometers need to be accurate to one decimal place. 1. The role of physical experiments: to provide rich perceptual materials for the development of physical laws, to test the correctness of physical theoretical hypotheses, and to open up new fields of physical application. 2. The role of physical experiment in teaching: it can enable students to obtain rich perceptual knowledge and deepen their understanding of physical concepts, principles and theorems. It can cultivate students' observation and experiment ability, thinking ability, and develop students' intelligence. It can make students initially understand the thinking methods and research methods of physics, and cultivate students' scientific attitude of seeking truth from facts and good quality of abiding by discipline and caring for instruments.