Extech 80359 Mini Hygro-Thermometer
This compact digital unit works in a guitar case or in-room settings to monitor the relative humidity levels and help protect your guitar from the adverse effects of high or low humidity. Easy-to-read display shows temperature and humidity simultaneously. RH range: 10 to 99% (+/- 5%). Temperature range: 14 to 140 degrees F. Built-in memory stores MAX/MIN readings. Built-in tilt stand and LR44 battery. Low battery indicator. Dimensions: 2” x 1.5” x .63” (51 x 38 x 16mm). Note: 45-55% relative humidity is optimal for your guitar. To maintain proper levels, you may need to use a guitar humidifier.