The DM-535 handheld thermo-hygrometer provides simultaneous display of relative humidity, temperature, dew point, and absolute humidity readings. It is equipped with a high-accuracy humidity and temperature transmitter that provides an RS-232 signal to the handheld display. The RS-232 digital signal format allows the simultaneous display of four measurands, on a two-line LCD, without the need for a display selector switch. Transmitters are available for English or metric units. The transmitter, coiled cable, and handheld readout together weigh 10 ounces, making it portable. The unit uses a single 9-V battery.