The Measurement Shop's Guide to Moisture Meters

What is a moisture meter?

Moisture meters (also called moisture detectors) are portable measuring devices used to measure the moisture content of a sample. These devices tend to include large displays for indicating moisture values in percentages, with some meters specifying whether a sample has a ‘low’ or ‘high’ amount of moisture in accordance with a pre-defined limit.

What is a moisture meter used for?

Moisture meters are used to calculate the moisture/ water content in a sample through electrical resistance. These meters are often used in a wide variety of applications and ensure organic substances such as wood, food, oils, gels and creams have an optimum moisture level in order to ensure the correct consistency and quality.

How is moisture measured?

Moisture content is measured as a percentage of moisture given off a given sample after heating or through measuring electrical resistance. Many digital moisture meters have a pre-defined low, optimum and high limit that can be easily referenced against a given result.

Can a moisture meter detect mould?

Mould is a regular concern when dealing with wooden products, therefore it is crucial that forested areas as well as individual trees are carefully monitored to ensure the prevention of fungi and quality of the wood over time. Moisture meters can be used to detect mould or prevent fungal growth and spread on wooden surfaces; moisture content readings above 20% allow mould spores to develop.

Moisture analysers are frequently used in the food industry for preventing premature mould growth. Food products such as biscuits require an optimum moisture level to ensure that the biscuit has the correct consistency and taste; too little moisture may cause biscuits to crumble apart, whilst too much moisture encourages the growth of bacteria. Moisture analysers are often preferred for detecting mould.

Types of moisture meter

Pin Moisture Meters

Pin type moisture meters are portable, hand-held devices that include 2-4 small, steel probes used to penetrate a sample in order to give an accurate moisture content reading. Once the probes have penetrated the material, an electrical current is passed between the two points and the resistance is interpreted into a moisture content value. Pin moisture meters offer a greater variety of depth readings compared with pinless models.

Applications:

• Building & construction – drywall, plaster, concrete, wood,

Hygrometers

Hygrometers are a specialist type of moisture meter used to detect relative humidity and measure water vapour in organic samples and the atmosphere. Most modern hygrometers use condensation temperature (sometimes referred to as ‘dew point’) and electrical capacitance to measure differences in humidity. Types of hygrometer can be categorised into capacitive, resistive, thermal and gravimetric.

Applications:

• Agriculture and farming – soil, plants and crops
• Forestry – trees

Moisture Analysers

Moisture analysers are high-end moisture analysing devices that are typically used in laboratories on a worktop or workbench surface. These devices often use a built-in halogen bulb to heat and dry samples, employing the Loss-On-Drying method (LOD) in order to determine the amount of moisture content in the sample.

Applications:

• Cosmetics – Gels, skin creams, lubricants, oils and hair products
• Agriculture and farming – Grain, wheat, rye, barley, cereals, hay and soil
• Pre-packed food – Biscuits, bread and crackers

Infrared moisture meter

Infrared moisture meters come equipped with thermal imaging sensors that can easily detect temperature measurement patterns in order to determine hidden moisture. Once discovered, a meter probe can be used to capture precise moisture content readings.

Applications:

• Building design – DIY and contractors

Non-destructive/ Pinless moisture meter

Pinless moisture meters (also known as non-destructive moisture meters or drywall moisture meters) are frequently used in building and construction for measuring moisture content with causing damage to materials. With a pinless moisture meter, you can simply press the meter against a flat surface such as plaster, drywall or frame in order to take moisture readings.

Applications:

• Building & construction – Plaster, drywall, timber, sheet rock, mortar and sealant.

Wood moisture meters

Wood moisture meters can be classified under pin moisture meters or hygrometers and are specifically designed to measure the moisture content in wood such as timber frames, oak and mahogany.

Applications:

• Woodworking & carpentry – Wooden furniture, wooden flooring and timber frames
• Forestry – Trees and roots

Soil moisture meters

Soil moisture meters are portable, digital meters specifically designed to measure moisture levels in soils, composts and vegetation. These meters can be pin or pinless and are frequently used by gardeners, farmers and conservationists to ensure optimum growing conditions for plants, flowers and crops. Hygrometers are often preferred for tropical greenhouse environments to ensure optimum humidity levels for certain species of tropical plants.

Applications:

• Agriculture & farming – Growing crops, wheat, barley, vegetables and oats.
• Gardening – Planting, trees, shrubs, tropical plants and flowers.
• Forestry – Tree growth and soil consistency.

How to use a moisture meter for measuring damp on walls

• Wipe off any residue or standing water from the wall surface.
• If checking loose panels, ensure you lie the panel on a flat surface for uniform measurement.
• Turn on the moisture meter.
• If using a pinless moisture meter: Press the meter against the wall and apply slight pressure. Pin moisture meters: press the small steel probes against the wall/ material and hold, making sure both probes lie flat against the wall.
• Wait for the value on the display to stabilise (this should only take a few seconds).
• Once stabilised, depending on the type of device being used, an icon should appear on the display to indicate a low, medium or high level of moisture content along with the moisture value as a percentage.

Things to consider:

1. Ensure you have adequate battery charge before conducting readings.
2. Ensure you have positioned the sample on a flat surface.
3. Ensure all moisture or residue has been removed from the surface of the sample.
4. If using pins, check that these have been installed correctly and are free of damage as this can effect results. Replacement pins can be purchased from a variety of moisture meter suppliers.

How to calibrate a moisture meter

The calibration procedure will differ depending on the type of moisture meter you are using, however, most pinless models can be calibrated using a specially designed calibration block or kit from the manufacturer. For more specific information about the calibration procedure on your device, please contact the manufacturer.

How to interpret moisture meter readings

Moisture meters provide percentage readings based on the amount of moisture given off a sample through electrical conductivity/ resistance testing. The results from moisture determination procedures should be interpreted with the aid of a moisture content guide specific to the material you are testing, for example, when testing wooden logs. Certain types of moisture meter will categorise the results into a low, medium or high moisture content based on percentage ranges, for example, 75%-100% = High. Using our wooden logs example, newly cut logs will have a moisture content of around 80% and above, dependant on the species of tree, placing this firmly in the High moisture content category. As the tree dries through either kiln heating or air drying methods, this percentage will gradually decrease. Carpenters and woodworkers monitor the drying process with a wood moisture meter until an optimum moisture percentage is achieved for fashioning furniture or flooring. Too much or too little moisture can cause imperfections in the wood including cracking, browning or buckling.

What is the difference between a moisture meter and a moisture analyser?

Moisture meters measure moisture content in terms of conductivity of a sample and come in many varieties that cover a wider spectrum of moisture analysis such as air humidity.  For example, pin moisture meters utilise a resistance principle which can measure electrical current through a given sample in order to provide more precise readings. In contrast, moisture analysers now rely upon a Loss-On-Drying (LOD) principle which uses a built-in halogen bulb to effectively dry and heat samples in order to measure moisture content by the amount of moisture evaporating off the sample.

In addition, moisture analysers are typically larger, more advanced measuring devices required for specialist testing that are confined to lab workbenches. In contrast, moisture meters are fully portable and allow moisture readings to be taken on the move or in outdoor environments that do not have access to power mains.

What is the best moisture meter?

The best moisture meter will largely depend on your requirements. Reed’s Pin and pinless moisture meters are recommended for moisture analysis in building materials such as wood and timber in order to use electrical current as a method of moisture detection. Humidity meters (also known as hygrometers) are designed specifically for calculating air humidity and temperature. If conducting moisture analysis on food products, you may require a halogen bulb moisture analyser, such as those manufactured by Adam Equipment or A&D that can simulate the heating and drying process for highly precise moisture readings.

Our recommended moisture meter products

Reed R6013 Wood Moisture Meter

Portable, pocket-sized moisture meter manufactured by Reed Instruments. The R6013 includes a large LCD display and pins for measuring moisture in wood and a wide range of building materials.

Reed R6018 Pin/Pinless Moisture Meter

Reed’s R6018 moisture meters can be customised for pin or pinless testing. Pin functionality ensures the measurement of moisture between the two steel probes, whilst the pinless option allows for the non-destructive testing of more fragile materials.

Reed R6001 Thermo-hygrometer

Reed’s thermos-hygrometer is a compact, portable device that measures ambient temperature and humidity simultaneously. These devices are frequently used to test humidity in greenhouses, humidors, HVAC system installations, saunas and food distribution environments.

PMB Moisture Analyser

Adam’s PMB moisture analyser includes a total of 7 pre-set drying modes for allowing a variety of test routines to take place. The PMB comes with 3 settings for heating samples including ramp-up, stepped temperatures and single temperatures. Ideal for precise sample analysis in cosmetic and food testing labs.

A&D M series Moisture Analyser

A&D’s M series of moisture analysers utilise built-in halogen lamp heating with a uniquely designed Secondary Radiation Assist filter that provides shorter measurement time with fast, uniform heating. The sample pan features an easy-to-move, practical design that eliminates mishaps such has burns when moving hot sample trays into or out of the unit.