See below for frequently asked questions within the Building and Agricultural industries.
Protimeter moisture meters are calibrated for wood but are also suitable for measuring moisture levels in other materials. They are highly versatile tools for assessing the moisture condition of a wide range of non-conductive materials. In wood, the instruments measure the material’s actual percent moisture content (%H2O). When testing material other than wood, the meters measure the wood moisture equivalent (WME) value of the material. WME is the moisture level that would be attained by a piece of wood in equilibrium with the material being tested. As the critical moisture levels for wood are known, WME measurements enable the moisture meter user to establish if materials are in a safe air dry, borderline or damp condition.
Relative humidity (%rh) is the degree of saturation – or the amount of water vapour that air contains – relative to the amount it would contain if saturated. This is often expressed as a percentage, so saturated air at a given temperature has 100%rh. If air is warmed, the amount of water vapour it could hold at saturation is increased. Consequently, the %rh value falls, even though the actual amount of water remains constant. Similarly, if the air is cooled, the amount of water vapour it can hold is reduced. Consequently, the %rh value rises. Condensate forms when there is an excess of water in saturated air.
If a dry and absorbent material, such as wood or brick, is placed in a very damp environment (high %rh) it will absorb water and its moisture content will increase. Conversely, absorbent materials with high moisture content will lose moisture to a dry environment (low %rh). The movement of moisture from material to environment and vice versa continues until the vapour pressures (within the material and the environment) have equalised. When this condition is reached, the moisture level of a material can be expressed in terms of equilibrium relative humidity (ERH).
ERH techniques are very useful for assessing if structures are in a dry, borderline or damp condition. For example, when the ERH of a concrete floor falls to 75, a flooring contractor knows that it has dried sufficiently for a decorative floor covering to be laid.
Dewpoint is the temperature at which a sample of air becomes saturated. Condensation forms on surfaces whose temperature is equal to or lower than the prevailing dewpoint temperature.
•<18% (Green Zone) - The material is in a Safe Dry condition, moisture related problems of decay/deterioration will not occur.
•18% - 20% (Yellow Zone) - The material is in a Borderline condition, decay/deterioration may occur under certain conditions.
•20% (Red Zone) - The material is in a Wet condition, decay/deterioration is inevitable in time unless the moisture level of the material is reduced.
Artificially high moisture meter readings may be obtained in material that;
•(i) has been heavily contaminated by hygroscopic salts, or
•(ii) in materials that are conductive by their own nature.
In the case of hygroscopic salts, the presence (or otherwise) of nitrates and chlorides should be established when investigating suspected rising dampness situations in particular. This can be achieved with the Protimeter Salts Analysis Kit (BLD4900).
If the material being tested is conductive - such as clinker block work - an alternative moisture measurement technique should be used. A hygrometer could be used to measure the material’s ERH, or its actual moisture content could be determined with an Ashworth Instrumentation Speedy™ tester.
During harvesting and drying, the moisture level within individual grains may not be evenly distributed. Grain that has been exposed to rain showers would have a wet husk, but it may be sufficiently dry at its core. Conversely, grain from the drier may appear to be very dry on its surface, but may still have excessively high moisture levels within it. Representative and reliable moisture readings can only be obtained under these circumstances by measuring a ground sample that has been compressed onto the measurement cell of the moisture meter. The grinding ensures that unrepresentative moisture levels on the surface do not skew the measurement and the compression ensures consistency and repeatability.
Automatic Temperature Correction (ATC) is a facility that corrects the moisture measurement of a sample with respect to its temperature. Protimeter moisture meters are calibrated at 20°C; if the temperature of the sample is significantly above or below this figure, the moisture measurement requires correction to account for changes in electrical characteristics. All Protimeter moisture meters automatically correct for the effects of temperature on moisture measurements. For this reason, Protimeter recommend that the ATC function is always active when measuring the moisture level of crop samples. ATC should only be deactivated when using the ‘Quickcheck’ device to check the calibration of the instrument with respect to factory settings.
If the crop to be tested is not pre-programmed into the instrument, a moisture reading is taken using the 0-100 relative scale. The value is noted, and reference is made to the Protimeter Crop Calibration Data table. This table, supplied with all Protimeter moisture meters, enables the user to convert the relative reading into the actual moisture content value.
A 'Quickcheck' device is supplied with all Protimeter grind-compress moisture meters for checking the instrument’s set up and calibration. If the meter readings are not within the stated tolerance as given in the instruction manual, you are advised to return your instrument to the Protimeter Service Centre for servicing.
Most Protimeter grain meters can be used with optional temperature probes for this purpose. To find out if a Temperature Probe is available for your existing meter, please contact us and advise what model of instrument you are using.
There are four key requirements that must be satisfied if grain is to be stored safely:
1.The moisture content of the grain should not exceed 15%.
2.Temperature gradients within the grain should be evened out and the bulk temperature should be reduced to the lowest possible level.
3.The grain must be protected from moisture ingress and condensation.
4.The grain must be protected from pests including insects, mites, birds and rodents.
For further information on these topics please refer to the Protimeter booklet 'CARE OF GRAIN' that can be downloaded from the Downloads page of this site.
What can I do if there is a discrepancy between my moisture meter reading and that of my merchants or other party?
There are many variables that subtly affect the calibration of moisture meters including measurement technology, crop variety, and soil types, growing conditions and geographical regions. One has to accept, therefore, that moisture meter measurements are subject to working tolerances, and modest discrepancies between different meters are to be expected. Protimeter grain moisture meters have a facility to adjust calibrations, if required, to account for these variables. For example, pragmatic farmers may choose to compare the results obtained on their moisture meter with those of their merchant on a sample at the beginning of the season. If there is a discrepancy, they may agree to match their meters by adjusting the calibration of particular crops.
The grain temperature affects the relative humidity in the voids between the kernels. Low temperatures reduce the amount of water available to mites and moulds and vice versa, so the storage temperatures should be reduced to minimum sustainable levels because, practically speaking, cooling has the same effect as drying. A graph showing the relationship between temperatures and moisture levels is reproduced in the Protimeter booklet ''CARE OF GRAIN' that can be downloaded from the Downloads page of this site.