EMC Wafer

EMC wafers are made from cellulose material. The cellulose quickly adapts to the relative humidity of the surrounding air, and thus allows direct EMC measurements. To give accurate EMC values, the Lignometer K and Ligno-VersaTec come with calibration settings specific to the cellulose wafer. Wireless monitors and kiln control systems are also pre-set to give accurate EMC values.

To obtain measurements the EMC wafer is placed into the EMC holder and connected with mounting plate and cable to moisture meters, monitors and kiln control systems.

EMC or equilibrium moisture content is the moisture content wood will acclimate to, if the present relative humidity does not change. This value is measured with the EMC wafer directly. See EMC-Chart.


Item Number: K-EW

Starting at $15.00

Product Description

The small, flat and thin wafer is made from a cellulose material. Size of the wafer is 1.5″ x 1″ (2.5cm x 3.8cm) The material is specifically selected to acclimate quickly to the surrounding air. The meters, wireless monitors and kiln control systems are set to indicate accurate EMC values.

In order to measure the wafer, the EMC holder is needed. The EMC holder consists of 2 sets of measuring plates, which hold the EMC wafer and 2 banana plugs, which are plugged into a mounting plate or angle connector. From there, a cable connects to the moisture meter Lignometer K and Ligno-VersaTec via Adapter H or Lignomat’s kiln control systems and wireless monitors.

Using EMC wafers in dry kilns to measure humidity is an excellent choice. The cellulose EMC wafers are inexpensive, reliable and not affected by the corrosive air nor by high temperatures inside lumber dry kilns. Measuring elements in relative humidity probes and thermo-hygrometers will likely be destroyed within a few months by the corrosive air in a dry kiln. Wet-bulb dry bulb thermometer stations are cumbersome to maintain. Lignomat has used EMC measurements with cellulose wafers in lumber dryers and predryers for over 50 years.

Measuring EMC: The cellulose wafer quickly reaches an equilibrium with the surrounding air wherever it is placed, inside a dry kiln, air drying shed, warehouse, shop, house or office. To obtain EMC measurements, connect the Ligno-VersaTec or the Lignometer K, select the EMC setting and the correct temperature and the meter indicates the EMC value for the relative humidity and temperature of the surrounding air. The kiln control systems and wireless monitors automatically correct for the EMC setting and the temperature and produce corrected EMC values.

EMC Charts: Corresponding values for stable conditions of relative humidity / temperature and wood moisture content are listed in the

— EMC-Chart up to 100°F
— EMC-RH-WB Chart up to 210°F
— EMC-RH-WB Graph for kiln-drying up to 260°F

At a temperature of 70°F and 45% relative humidity, the EMC according to the chart is 8.5 %.  That means, wood with a moisture content of 8.5% is stable, it will not absorb or loose any moisture, will not shrink, warp or cup. If wood in the same ambient conditions has a moisture content of 10.5%, it will loose moisture until 8.5% has been reached. This loss in moisture can cause wood movement depending on wood species, wood thickness and time of exposure.

Looking at drying conditions in dry kilns or wood sheds: If the moisture content of wood is 15% and the EMC of the surrounding air independent of the temperature is also 15% no drying will take place. If the moisture content of the wood would be 22%, there is a moisture gradient and the wood will dry. Lignomat has been using EMC measurements from cellulose wafers for over 50 years to control the drying process in kiln control systems.


— EMC wafer
— EMC Holder
— Angle connector
— EMC mobile mount: EMC holder with plate to slide into stacked lumber
— PK-H cable to plug into angle connector, measuring station and mobile mount.

— Ligno-VersaTec
— Lignometer K
— Kiln control systems
— Wireless monitor

mini-Ligno DX/C can be used, but the accuracy above 10% may not be enough. Lignometer and VersaTec indicate moisture with a 0.1% resolution for the entire range.

For more information please contact Customer Service at 1-800-227-2105.

Lignomat USA Ltd, 14345 NE Morris Ct., Portland OR 97230, USA,
Email: sales@Lignomat.com, www.Lignomat.com