this series of water bath, a kind of multi-functional thermostatical circulating water bath, is comprised by thermostat with high-accuracy and compressor-cooling system through adopting micro-processing technique together with pid control method. this kind of water bath is widely applied to such fields as petroleum, chemical industry, medicine, biochemistry, measuring, light industry, laboratory of the r&d institution, etc. it is very safe and reliable to use this kind of products.