The Rotronic HygroPalm HP31 handheld humidity meter utilizes a fixed probe to measure and log relative humidity, temperature, and perform psychrometric calculations including dew/frost point, wet bulb temperature, enthalpy, vapor concentration, specific humidity, mixing ratio, vapor pressure, saturation vapor pressure, and saturation vapor density. The graphical display allows graphs and up to four values.

Additional functions include spot measurements, time-programmable interval logging (1s to 24h), min/max/average capability, and programmable visual and audible alarms. On-board memory capacity is 64,000 data points, with data transfer via micro USB port. The HP31 is compatible with HW4 software (LITE version included). The integrated 3.7V, 1000 mAh lithium polymer battery provides up to 10 hours of use with screen always on or 48 hours when logging every 30 seconds with screen off. Probe application range: -10 to 60°C / 0–100% RH. IP65 protection.