I bought 4 sensors of this type. And all 4 worked fine for 6-7 months. Unfortunately, after this period and after changing the batteries in all the sensors, I found that 2 out of the 4 were experiencing inexplicable battery drain, resulting in the batteries not lasting more than 3-4 days. Therefore, I choose to give it 3 stars because it had good functionality and I believe that maybe I was just unlucky and got a faulty batch.