Active Standard ASTM C1789 | Developed by Subcommittee: C11.01
Book of Standards Volume: 04.01
Significance and Use
5.1 This Standard Test Method is intended for use in calibrating hand-held meters to accurately read from approximately 30% to 90% ERH. Moisture content is related to the ERH or water activity of a material.
5.2 Hand-held meters provide a rapid means of sampling the moisture content of gypsum boards and panels during manufacture and for field inspection during and after building construction. However, these measurements are inferential, that is, electrical parameters are measured and compared against a calibration curve to obtain an indirect measure of moisture content. The electrical measurements are influenced by the actual moisture content, a number of other gypsum board and panel variables, environmental conditions, the geometry of the measuring probe, and the design of the meter. The maximum accuracy can only be obtained by an awareness of the effect of each parameter on the meter output and correction of readings as specified by these test methods.
5.3 Electrical conductance and dielectric meters are not necessarily equivalent in their readings under the same conditions. When this test method is referenced, the type of meter that is being used must be reported with the relevant ranges for precision and bias as specified in this standard.
5.4 Both types of meters are to be calibrated with respect to ERH as described in this standard.
1.1 This test method applies to the calibration of handheld moisture meters for gypsum board, glass faced gypsum panels and fiber-reinforced gypsum panels by means of electrical conductance and dielectric meters. The test uses wetted test specimens which are dried down in at least 5 steps to determine the moisture content based on the weight loss in comparison to the dry weight. The test also supplies the ERH values for each of the drying steps.
1.2 This test method applies to the field use of hand-held moisture meters at storage and distribution facilities, construction job sites and in buildings.
1.3 This test method has not been evaluated for the influence of paint or wall covering materials on the indicated moisture content of a gypsum board or panel substrate.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
C473 Test Methods for Physical Testing of Gypsum Panel Products
C1177 Specification for Glass Mat Gypsum Substrate for Use as Sheathing
C1178 Specification for Coated Glass Mat Water-Resistant Gypsum Backing Panel
C1278 Specification for Fiber-Reinforced Gypsum Panel
C1396 Specification for Gypsum Board
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
ASHRAE Standard2009ASHRAEHandbook&n Chapter 1 - Psychrometrics, American Society of Heating, Refrigerating and Air-conditioning Engineers
ICS Number Code 91.100.10 (Cement. Gypsum. Lime. Mortar)
UNSPSC Code 41112304(Moisture meters)