Vaisala HUMICAP HM70 - 1 Introduction to HM70

1 Introduction to HM70
Vaisala HUMICAPâ Handheld Humidit
y 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 consists of 2 main units: Vaisala Handheld Measurement
Indicator MI70 and the HMP75/HMP76/HMP77 probe.
HM70 can be used to measure the following parameters:
Table 1 Display parameters
Parameter Abbreviation Metric unit Non-metric unit
Relative humidity RH %RH %RH
Temperature T °C °F
Dew point/frost point temperature
1)
T
d/
f
°C °F
Dew point temperature
2)
T
d
°C °F
Absolute humidity a
g/m
3
gr/ft
3
Mixing ratio x g/kg gr/lb
Wet bulb temperature T
w
°C °F
Humid air volume/dry air volume H
2
O ppm ppm
Water vapor pressure pw hPa
lb/in
2
Saturation water vapor pressure pws hPa
lb/in
2
Enthalpy h kJ/kg Btu/lb
Water activity a
w
aw aw
1) T
d/
f
shows dew point temperature above the freezing point (0 °C/32 °F) and frost point
temperature T
f
(dew point over ice) below the freezing point.
2) T
d
shows dew point over water throughout the entire measurement range.
This Quick Guide introduces the features of the MI70 indicator and the basic measurement
pr
ocedure with the HM70 meter.
The HM70 User Guide (M210297EN) at www.vaisala.com/hm70 contains product specifications
and instructions for operating and maintaining HM70, and using it together with the following
Vaisala instruments: HMT120, HMT140, HMT330, PTU300, HMT310, and HMP155.
Using HM70 with other Vaisala instruments is discussed in the respective User Guides, also
available at www.vaisala.com:
• HMP60 and HMP110 Series User Guide (M211060EN)
• HMDW110 Series User Guide (M211726EN)
• HMW90 Series User Guide (M211399EN)
M212070EN-B
6