I just wanted to mention my new CHEAP EXTERNAL DIGITAL Thermometer and Hygrometer (humidity tester/monitor), which cost me all of $23.00 with Tax. At the same time, give it a review. Source: Petsmart Brand: All Living Things Reptile Habitat Thermometer & Hygrometer Sensors: Temperature and Hygrometer Specs: Separate lead wires to the sensors for easy internal placement. Display- External Accuracy: Tolerable based on price. Type: Digital Link: http://www.petsmart.com/reptile/hum...-hygrometer-zid36-5195367/cat-36-catid-500012 After tolerating my array of Glass and Digital Thermometers, from the AccuRite brands as well as 2 human digital's “ReliOn” from the RX section at Wal-mart, I decided I have had enough. They were bulking up the inside of my incubator and causing me to constantly question actual Temps and humidity, spite the general readings and my having to perform calculations to arrive at a statistical estimate of temp and humidity. Enter “All Living Things Reptile Habitat ....” a small thermometer and Hygrometer for pet terrariums, aka exotic reptiles and other beastly critters that require temperature and humidity control. My current units were all housed internally in the incubator and I expressed this to the PetSmart floor clerk. I told him that I wanted external sensors (lead wires for both sensors) so I could mount the display as an external unit and the sensors inside (internal) my incubator. The floor clerk showed me the unit mentioned above and I told him that I did not think it would be what I wanted, spite the fact that it had two separate long leads to the both sensors. It just looks cheap and there's no way to calibrate it was my comment! In his reply, he said you can always bring it back if you keep the receipt, given the 60 day return policy. Spite my complaints, my cheap nature took over and I was sold. Honestly, I did not think much of the unit over my current bulky set up but was willing to try it. I suspected that it would be inaccurate and I would still have to prove my math skills. Upon putting the Watch Battery in the unit and a few button pushes, I had the time and date set, along with my favorite Fahrenheit setting over Celsius. Still the unit started grabbing readings immediately after I put the battery in. My largest concern was how would I know how accurate it was? Two quick test will tell me what I need to know so I grabbed some Sea Salt or Salt, some Ice cubes, a zip lock bag, some water and a cup with a lid. Humidity calibration on the high end can be determined by making sludge of salt and water but it must be thick like a paste. This concoction will give you a consistent 75% humidity reading so you can calibrate or Calculate the difference in humidity readings. Note: This does not cover the more expensive and accurate hygrometers that can be calibrated on the High and Low ends, I am working on a budget. Humidity Test- I mixed up a batch of the salt solution and hung the sensor over it over the mixture (not submerged in it) and put the lid on top. The result was noted after 20 minutes (74.3%), but the 4 hours endurance result was a reading of 74.1% humidity. So the units sensor was off by 0.7 to 0.9, Good enough for me! Temperature test- I grabbed some ice cubes and water in a cup and allowed it to cool which should give me a 32 degree Fahrenheit reading. I put the temp sensor in the zip lock bag and submerged it and waited about 20 minutes. My sensor reading floated between 30.7 and 30.9 degrees Fahrenheit, and did so over the period of 2 hours, but the sensor seemed to like the 30.9 degree reading more. Good enough for me and close enough for incubating eggs. 30.9 is 0.1dg from 31 dg F so I say off by 1 degree. (-+1 degree). All my other units were tested as being off by 4-12 degrees F and off in humidity by 10-15%. Well there you have it! Over my array of digital and analog thermometers and hygrometers cheap-os, this unit replace 4 units. PetSmart device seems to pass with flying colors and is more accurate than all the others combined; plus the sensors are external so no more bulk inside my incubator. Only time will tell if it keeps its calibration. I just hope that watch battery will last, I bought extras!