Protimeter Hygromaster2 Sub-Surface Moisture Meter

This Hygrometer is used to measure the Equilibrium Relative Humidity (ERH) of walls, floors and surface of concrete.

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Protimeter Hygromaster2 Sub-Surface Moisture Meter

The Hygromaster displays relative humidity, ambient temperature and dewpoint (with optional surface temperature probe). Measures concrete moisture via humidity sleeves or humidity box.

The Hygromaster is available in two options. One is designed for the flooring market (supplied with a Hygrostick) and the other is for General Measurement (supplied with a Quikstick) 

The Hygrostick (humidity sensor) reads Relative humidity to access the moisture condition/content in solid structures such as concrete floor slabs and walls.

Surface temperature probe is also available.

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  • Customer asks one of our laboratory staff about using the Hygromaster in a concrete slab that is outdoors and is three months old. He took readings on a slab that was 15°C and getting readings of 76.9%rh and 78%rh. When he measured the same slab at a later date in the same locations at a slab temperatures of 6°C the readings were 90.6%rh and 90.9%rh. The probe was left in each sleeve for 30 minutes on each occasion. He asked why the high readings? Is it due to the colder slab temperature of 6°C?

    Initially let’s make two assumptions. In both cases the hygrostick used to take the measurements was correctly calibrated and was in equilibrium with the environment (the air in the hole) being measured. The saturation vapour pressure of water depends strongly on temperature. Near room temperature, the air’s capacity to hold water vapour doubles for every 10°C increase in temp. But at, say, -60°C the saturation vapour pressure doubles for only a 5°C increase in temp. (Source: A Guide to Measurement of Humidity, NPL). In short this means that the measured rh value will change significantly with temperature, even when the actual moisture level within the concrete and the air pocket itself are more or less constant. As the temperature falls, the rh value will rise and vice versa. So if the slab temp has fallen from 15°C to 6°C it is no surprise that the rh values have increased significantly.

    A thought regarding this situation. It is odd that there should be such a variance in the temperature of the slab. Generally speaking, slab temperatures tend to be pretty stable, varying by only a few degrees C irrespective of the external environment once below the surface. This is one of the reasons why rh measurement is considered a practical option for assessing the moisture condition of a slab. Any explanation on how/why the slab temperature varies so much? Is there a subfloor heating system installed?

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  • Do the timber moisture meters work on MDF?

    The fact that timber instruments start measuring at 6-7% moisture content in timber does not preclude their use for other materials at lower moisture contents. Eg. In plaster board moisture content as low as 2% may be measured. Similarly, since we do not know exactly what the MDF consists of, the easiest way is to get a sample, which has a moisture content of 4% and see if one of our timber instruments work.

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  • Can the Mini or Surveymaster with deep wall probes measure moisture in vermiculite?

    Suggest a Mini with a deep wall probe for quick initial investigation. Then a Hygromaster could be used to measure the ERH if the material is of a compressed nature.

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Hygromaster - Flooring MarketHygromaster - General Use
Dimensions 7" x 3.2" x 1.5" (178mm x 81mm x 38mm)
Power 9V Alkaline
Infrared Surface Temperature Range

IR Based - with 12:1 (D:S) Ratio

Range -4°F to 176°F (-20°C to 80°C)

Accuracy ±3.6°F ( ±2°C)

Hygrostick Data (Nominal)

30% to 40% RH (±3% RH) at 68°F (20°C)

41% to 98% RH (±2%) at 68°F (20°C)

Range 32°F to 122°F (0°C to 50°C) ±0.6°F (±0.3°C)

Not Included
Quikstick & Quikstick ST Data (Nominal) Not Included

0% to 10% RH, ±3% RH at 68°F (20°C)

10% to 90% RH, ±2% RH at 68°F (20°C)

90% to 100% RH, ±3% RH at 68°F (20°C)

Range 32°F to 122°F (0°C to 50°C) ±0.6F (±0.3°C)

Nominal respose 30% to 90% and back to 30% RH in 45 seconds at 68°F (20°C)

Data Storage

Store up to 8,000 results with date and time stamp from all instrument functions with the push of a button. Store 6100 results with automatic logging.

Product Options

Select any product options you wish to enquire about:

  • Protimeter Hygromaster2 - Flooring Market

  • Protimeter Hygromaster2 - General Use


Calibration is done by comparison to a Test Box, with reference to a NATA endorsed Report, to provide equivalent moisture values according to the manufacturer. Calibration is done in accordance with Reference Document LWI 34.

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