The Model 657-1 Transmitter provides two 4-20 mA channels to produce separate output signals for both relative humidity and temperature. This inexpensive device delivers ±2% accuracy for humidity and ±3% for temperature measurements. The sensor employed in the 657-1 features a state-of-the-art integrated polymer film humidity sensor and a thin-film platinum temperature sensor to assure high reliability and rock-solid stability over years of continuous service. Stainless steel probe measures 5/16" x 10" (0.8 x 24.4 cm) and can be easily mounted to most ductwork using either of the two optional kits.