Product name: Altimeter and barometer with compass and thermometer Model: BKT381 Weight: 180g Packaging size: 14.5cm*11cm*3.5cm 1. Measuring range: (altitude) 0~5000m; (air pressure) 580~1040hPa; (temperature) -30~50 2. Resolution: 20m 3. Specifications: 85mm long 68mm wide 28mm high, dial diameter 60mm 4. Measurement accuracy error: 0 to 3000m height error plus or minus 30m, above 3000m error plus or minus 50m Air pressure error plus or minus 5 hPa 5. Storage conditions: temperature between -30 and 65; humidity less than 90% Product Overview: This product is a barometer altimeter with a built-in sensitive air pressure sensor that can measure the real-time atmospheric pressure value of the location; due to the principle that altitude and atmospheric pressure are inversely proportional, it can be used to measure relative altitude; after the altitude value is corrected, the real-time altitude can also be measured. This product is widely used for air pressure measurement, as well as outdoor occasions such as mountaineering and fishing, but it is not recommended for geographical surveys! For details, please see the graphic description below. The compass and small thermometer are only decorative. After all, they are too small and not very sensitive. If you want to use these two functions, please search for professional compasses and thermometers in this store. I. Product Introduction 1. This product is designed based on the physical principles: (1) Air pressure decreases with increasing altitude; (2) Changes in air pressure will lead to changes in weather, which will be displayed on the dial of this altimeter through a high-precision transmission device. This device can accurately measure the height of the location (absolute height), height difference, atmospheric pressure and predict weather changes. 2. No batteries and chargers are required, no maintenance and repair are required, it is a good tool worthy of trust; 3. Future weather changes can be predicted based on the air pressure value, so that you can be prepared; 4. Easy to carry and reasonable design, it brings ease and convenience to your outdoor sports. Note: The compass and thermometer provided are not suitable for occasions with high accuracy requirements! 2. Introduction to use 1. Absolute height measurement The altimeter should be initialized before use (or after purchase) (see the above diagram for operation), that is, the altimeter number is adjusted to the actual local altitude. Please note at this time: please refer to the marked altitude on the map (you can also check the local altitude on the Internet and the local meteorological bureau) to calibrate the exact altitude of the location. In addition, changes in air pressure and weather will also continuously affect the altitude value, so it is necessary to constantly compare the reference altitude value during climbing or walking. For example: The altitude of the starting point A is 200 meters from the Meteorological Bureau. The altimeter pointer is adjusted to 200. When the altimeter reaches position B, the dial scale is 1500, so the altitude of point B is 1500 meters. 2. Relative altitude During mountaineering or travel, if you need to measure the environmental altitude value, please follow the following two steps: (1) Initialize the altimeter at the starting point, that is, only align it with the 0 scale; (2) During the travel or at the end point, the scale value displayed on the dial is the altitude value relative to the starting point For example: At the starting point A, the altimeter is adjusted to 0 scale. When the altimeter reaches position B, the dial scale is 1500, which means that the altitude of point B is 1500 meters higher than that of point A.