Simple to operate — just saturate the wick of the wet bulb thermometer in clean water and whirl the sling psychrometer until the temperature stops dropping. Read the two thermometers. Place wet bulb temperature over the dry bulb temperature scale on the slide rule — the arrow will then point directly to the accurate relative humidity. That's all there is to it! Carry it in your pocket. Comes compete with carrying case and slide rule. Range on thermometers is 20 to 110°F.
Generally leaves the warehouse in 1-3 business days.