Active Standard ASTM D6782 | Developed by Subcommittee: D07.01
Book of Standards Volume: 04.10
Historical (view previous versions of standard)
Significance and Use
4.1 In-line meters provide a rapid means of detecting moisture content of lumber or wood products in processing (that is, on a continuous production line). Two major uses are monitoring the performance of the drying process (air drying, kiln drying), and providing sorting or identification of material at predetermined levels of moisture content. These measurements are inferential in the sense that physical measurements are made and compared against calibration curves to obtain an indirect measure of moisture content. These measurements may be influenced by one or more physical properties such as actual moisture content (average and gradient; see Appendix X5), density, surface moisture, chemical composition, size, and temperature of wood. In addition, the measurements may also be influenced by environmental conditions and the design specifications of the meter. The best performance is obtained by an awareness of the effect of each parameter on the meter output and correction of readings as specified by these test methods.
4.2 The two major anticipated users of these test methods are instrument manufacturers whose primary concern is laboratory standardization and calibration, and instrument owners who may have a primary focus on field standardization and calibration. These test methods present the laboratory and the field as separate tracks (see Appendix X2).
4.2.1 Laboratory Standardization and Calibration—This portion of these test methods is intended for guidance of equipment manufacturers. Specific test recommendations are tailored to the capabilities of a laboratory environment.
4.2.2 Field Standardization and Calibration—The predominant use of in-line meters is in production in which lumber characteristics and environmental conditions reflect actual mill processes. Field standardization and calibration is essential to address or encompass much of the variability in production.
1.1 These test methods apply to instruments designed to detect, or measure, moisture in wood which has been dried below the fiber saturation point. The purpose of these tests is to provide a unified standard against which such systems can demonstrate their suitability for their intended use (see Appendix X1).
1.1.1 Sensitivity to thin layers of surface moisture such as caused by dew or brief rain exposure is not addressed by these methods. Applications, such as screening material for surface adhesion, may require additional assessment methodology and criteria (see Appendix X5).
1.2 The standard is configured to support tests by moisture meter manufacturers as well as end-users of such systems, therefore the text follows two tracks (see Appendix X2).
1.3 Test methods specified for manufacturers are generally designed for laboratory settings and are intended to provide a standard against which a manufacturer certifies calibration and general system conformance.
1.4 Test methods for end-users are generally designed for field settings and are intended as a standardized set of procedures for determining the suitability of a specific machine for a particular use.
1.6 Applications requiring sensitivity to and identification of localized wet areas are limited to general recommendations. The presence of wet-spots is the subject of Appendix X8.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
D1990 Practice for Establishing Allowable Properties for Visually-Graded Dimension Lumber from In-Grade Tests of Full-Size Specimens
D2395 Test Methods for Specific Gravity of Wood and Wood-Based Materials
D2915 Practice for Sampling and Data-Analysis for Structural Wood and Wood-Based Products
D4442 Test Methods for Direct Moisture Content Measurement of Wood and Wood-Base Materials
D4444 Test Method for Laboratory Standardization and Calibration of Hand-Held Moisture Meters
D4933 Guide for Moisture Conditioning of Wood and Wood-Based Materials
D5536 Practice for Sampling Forest Trees for Determination of Clear Wood Properties
ICS Number Code 79.040 (Wood, sawlogs and sawn timber)