Water heater, detection method thereof, control method thereof, detection device thereof and control device thereof

The invention discloses a water heater, a detection method thereof, a control method thereof, a detection device thereof and a control device thereof. The detection method comprises the steps that a first temperature and a second temperature of the inside of a water tank of the water heater are detected; the transmission time for detection sound waves to penetrate through the water layer of the water tank is obtained, and according to the first temperature, the second temperature and the transmission time, the remaining hot water amount in the water heater is calculated. The technical problem that due to the fact that the remaining hot water amount in the water heater is unknown, hot water is frequently used up in the use process is solved.