Introduction to HM70 - HM70

HM70 User Guide

Document code
English (United States)
Document type
User guide

Vaisala HUMICAP® Handheld Humidity and Temperature Meter HM70 measures relative humidity and temperature accurately in measurement range −70 … +180 °C (−94 … +356 °F), depending on the probe model. HM70 incorporates the advanced Vaisala HUMICAP® technology that enables reliable and high-performance humidity measurement. HM70 consists of 2 main units: Vaisala Handheld Measurement Indicator MI70 and the HMP75/HMP76/HMP77 probe.

Table 1. Display parametersHM70 can be used to measure the following parameters:
Parameter Abbreviation Metric unit Non-metric unit
Relative humidity RH %RH %RH
Temperature T °C °F
Dew point/frost point temperature 1 Td/f °C °F
Dew point temperature 2 Td °C °F
Absolute humidity a g/m3 gr/ft3
Mixing ratio x g/kg gr/lb
Wet bulb temperature Tw °C °F
Humid air volume/dry air volume H2O ppm ppm
Water vapor pressure pw hPa lb/in2
Saturation water vapor pressure pws hPa lb/in2
Enthalpy h kJ/kg Btu/lb
Water activity aw aw aw
1 Td/f shows dew point temperature above the freezing point (0 °C/32 °F) and frost point temperature Tf (dew point over ice) below the freezing point.
2 Td shows dew point over water throughout the entire measurement range.