Moisture Meters – Pins or Pinless?

Modern moisture meters have come a long way in the last few years, from the analogue moisture meters that used to be placed onto a material or wall and have the needle indicate whether something was dry or wet. Today’s moisture meters are sleek, accurate and easy to use products which give excellent results and are far more accurate than the moisture meters of old.

A decent moisture meter will range in price from around $200 to over $1,000 which is very much dependent of the features and the technology available. Something like the FLIR MR160, even 3-4 years ago, would have been unthinkable. With it’s built in infrared guidance technology, which works in a similar way to a thermal imaging camera, the FLIR MR160 has only been made possible due to the extensive development of the smaller Lepton IR sensor which makes the most up to date thermal imaging cameras and associated equipment, smaller than ever before.

However, the main question which still arises when a potential customer asks us about a moisture meter is whether a moisture meter with pins, or a pinless moisture meter is more suitable, and the answer to this question still is very much reliant on the potential application of the meter.

First of all though, it is necessary to understand the differences between the technology and how it works.

The traditional moisture meter with pins is based on the fact that a small electric current is passed from the end of one pin and into the material being measured. At different levels of moisture content, the resistance of the material changes and therefore has an effect on the passage of current from the end of one electrode tip to the tip of the other electrode, which completes the circuit. Different material groups have what are known as moisture curves, which simply put mean that one material at a certain level of conductivity will contain a certain percentage by weight of moisture. Another material, at the same conductivity may contain a different amount of moisture, and so the more material groups that are selectable in the moisture meter, the more precise it will be when used on different wood or building materials. The Testrite T-250 contains a large number of material groups. Cheaper moisture meters generally utilize the pin method and may have only one selector switch for building and timber for just very generalised readings.

A pinless or non-destructive moisture meter works by passing an electromagnetic field into the material being measured and detecting differences in this field which are caused by moisture content. The main benefit of using a pinless moisture meter is speed, as a pinless meter can scan larger areas much faster than a pin moisture meter. Additionally, the pinless moisture meter does not leave any pin marks or holes behind, so for some applications, a pinless meter would be the only choice possible, especially where cosmetic damage cannot be left behind. Some of the pinless moisture meters, such as the Caisson VI-D4 have a large footprint and so can read moisture in a much larger cross sectional area. Other meters, such as the Caisson GM-200 have a small spherical sensor, and read moisture in a much smaller area as only a very small surface area is in contact with the material being tested. Pinless moisture meters also read to a depth of typically up to 40mm, whereas the pin moisture meters read a small path directly between the two pins or electrodes.

There are many materials which can be measured with a pinless moisture meter as they use a relative mode of measurement. This means that essentially they are used by comparing an area of normal moisture content, with an area of suspected moisture content. The 0-100% found in some of the cheaper moisture meters is not related to the weight of moisture in percent but rather to the meter’s dynamic scale. Some of these pinless moisture meters, for example the Caisson VI-D4 and Caisson GM-200 have scales loaded into their operating system, so even in pinless mode, they can display the moisture content of certain materials as weight by percent.

In conclusion, a pin moisture meter will give a reading over a very small area (between the pins) so if an exact reading at an exact spot is required, then a pin moisture meter, such as the Testrite T-250 will suit the application better. If a non-destructive reading is required – without leaving any damage behind, then a pinless moisture meter is the obvious choice. Also it is worth bearing in mind that a pinless moisture meter can read to a certain depth as well, but the reading will be over a larger surface area than the pin moisture meter, but to balance that out, they are faster and the reading is far simpler to obtain. With pinless moisture meters, they can also be affected by metal objects, such as a nail or a metallic object in the wall, which will cause the reading to falsely spike. Overall though this is a fairly small issue and one we don’t really encounter very often at all.