The psychrometer and aerograph indicated the relative humidity. These quantities are readily estimated by using a sling psychrometer. It is partly affected by humidity, which can be measured by a sling psychrometer. Technically, the temperature registered by the dry-bulb thermometer of a psychrometer. A device used to measure humidity is called a psychrometer or hygrometer. The instrument used to record relative humidity is the psychrometer. When the psychrometer was first tried in the airplanes, the readings were inaccurate. A psychrometer is a device that includes both a dry-bulb and a wet-bulb thermometer.