The ACI Relative Humidity Outside Air Series utilizes a thermoset polymer capacitive sensing element with factory applied hygroscopic ­filter to deliver a proportional analog current or voltage output signal. The hygroscopic ­filter provides added resistance to moisture, dust, and other chemicals for greater long-term reliability. (For RH/Temp combination units, please see data sheet for temperature output specifications). The RH Outside Air transmitter features integral DIP switches for ­field selection of the proper output signal and supply voltage to meet your applications requirements. Each unit also contains 0%, 50%, and 100% test options to verify that the transmitter is both working and wired properly. Field calibration also can be performed by using the increment and decrement calibration DIP switches without the need to replace the sensing element. These enhancements provide increased flexibility and outstanding long-term reliability. Outside Air configurations feature a weatherproof enclosure with gasketed cover and conformally coated circuit boards for added moisture and chemical resistance. Three and Five-point NIST Calibration Certificates are available upon request but they must be ordered separately.