Review on Accurate Humidity Gauge 5-Pack: Newlight66 Digital Hygrometer Thermometer 🌡️ (°F) - Indoor Outdoor Hygrometer for Humidors, Home, Car, Greenhouse by Timothy Richmond

The product is advertised with an accuracy of 5%. I tested them using the salt water method. As you can see in the picture after 12 hours only 1 meter in 5 read within 5% and this was a 5% deviation. Other 4 devices show 7-8% less. For comparison, I put a higher quality hygrometer in my pocket, which gives the correct reading of 75%. Also, a higher quality hygrometer read 75% in just 4 hours. The cheaper models had more flaws and only reached the numbers in the photo after I left them there overnight. I believe if you calibrate them when you receive them and track the offset of each unit they can be used. Although with so many units this is a big problem.