The D'Addario Humidity & Temperature Sensor is a precision-designed hygrometer that digitally indicates accurate relative humidity levels ranging from low (under 20%) to 99%. Temperature is displayed in either Fahrenheit or Centigrade, ranging from -32°F to 122°F (-35C to 50C). The HTS includes a programmable set point, as well as a memory feature that indicates date/time of the highest & lowest temperature/humidity levels the instrument has been exposed to. Get one for each of your instruments. It's a wise investment to install and use a humidifier and sensor in each of your instrument cases.