Introduction to HMK15 - HMK15

HMK15 User Guide

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User guide

Vaisala Humidity Calibrator HMK15 has been developed for the calibration and checking of humidity probes and transmitters. The functioning of the calibrator is based on the fact that certain salt solutions generate a specific relative humidity in the air above them.

Figure 1. HMK15 calibrator and selected accessories
Calibration certificate for salt package
Ready-dosed salt package (accessory)
Measurement cup
Calibration adapter
Salt chamber with transit cover on
HMK15 basic chamber lid with rubber plugs
Base plate
Ion-exchanged water (accessory)

The four holes in the HMK15 basic chamber lid are designed for Vaisala probes and transmitters with 12 mm (0.47 in) diameter. The fifth hole is for the thermometer delivered with HMK15.

The HMK15 universal lid is suitable for probe models with 12 mm (0.47 in), 13.5 mm (0.53 in), or 18.5 mm (0.73 in) diameter.

Optional custom lids are available for Vaisala DMT132 dew point transmitter and Vaisala HMP60 and HMP110 humidity and temperature probes 1. For instructions on using HMK15 with DMT132 and HMP60/HMP110, see the respective user guides, available at

The following salt solutions, for example, are suitable for HMK15:
  • Lithium chloride LiCl (11 %RH)
  • Magnesium chloride MgCl2 (33 %RH)
  • Sodium chloride NaCl (75 %RH)
  • Potassium chloride KCl (85 %RH)
  • Potassium sulphate K2SO4 (97 %RH)

In calibration, the sensor head is inserted into a salt chamber containing a saturated salt solution. The reading given by the probe or transmitter is then adjusted to the humidity value that the specific salt solution generates at that particular temperature.

To ensure the sensor accuracy over the entire humidity range (0 … 100 %RH), calibration is usually performed at least at two different humidities.

HMK15 is suitable for both laboratory and field use. The chambers can be tightly closed for transportation with custom-designed transit covers. The optional transit bag (item code HM27032) allows the calibrator to be transported in vertical position or to be housed during calibration.

Accessories include additional salt chambers, ion exchanged water, transit bag, and ready-dosed salt packages: LiCl (11 %RH), MgCl2 (33 %RH), NaCl (75 %RH), KCl (85 %RH), and K2SO4 (97 %RH).

1 Vaisala item codes of custom lids: 230914 and 253277SP.