The Model 657-1 relative humidity and temperature transmitter includes two 2-wire circuits to simultaneously produce separate 4-20 mA output signals for relative humidity from 0-100% and temperature from 32 to 212F. Accuracy for humidity is ±2% from 10-90% and for temperature it is ±1F over the full range. The control operates both channels from a single 10-35V dc power supply wired into the relative-humidity current loop. The probe included with the transmitter features an integrated, polymer film, and a relative-humidity sensor plus a separate thin-film platinum sensor for temperature measurement.
Dwyer Instruments Inc., Box 373, Michigan City, IN 46361, FAX (219) 872-9057.