The Mamac Systems VA-921-VDC-7 Humidity Sensor is a replacement sensing component designed for compatible HVAC and building automation systems. It detects changes in relative humidity and converts measured conditions into an electrical signal that the control system uses to regulate ventilation, humidification, or dehumidification equipment. Suitable for compatible air handling units,... https://www.partshnc.com/va-921-vdc-7-mamac-systems-humidity-sensor