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Designation: B389 − 81 (Reapproved 2008)Standard Test Method forThermal Def l ection Rate of Spiral and Helical Coils ofThermostat Metal 1This standard is issued under the f i xed designation B389; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (´) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of the thermaldef l ection rate of spiral and helical coils of thermostat metal.1.2 The values stated in inch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to become familiarwith all hazards including those identif i ed in the appropriateMaterial Safety Data Sheet (MSDS) for this product/materialas provided by the manufacturer, to establish appropriatesafety and health practices, and determine the applicability ofregulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards: 2E77 Test Method for Inspection and Verif i cation of Ther-mometers3. Terminology3.1 thermostat metal, n—a composite material, usually inthe form of sheet or strip, comprising two or more materials ofany appropriate nature, metallic or otherwise, that, by virtue ofdiffering expansivities of the components, tends to alter itscurvature when its temperature is changed.3.2 thermal def l ection rate, n—the ratio of angular rotationto temperature change. It is a measure of the coil’s thermalactivity. It may have the units of angular degrees per degreeFahrenheit, or Celsius, and is expressed by the equation D= (A 2 − A 1 )/(T 2 − T 1 ) where A 2 and A 1 are angular positions attemperature T 2 and T 1 respectively.3.3 spiral coil, n—a part made by winding strip on itself.Fig. 1 and Fig. 2 show typical spiral coils, which can be woundwith the low-expansive side inside or outside, mounted on thespecimen holder.3.4 helical coil, n—a part made by winding strip in a formwherein the plane of the width of the strip is parallel to theaxial length. Fig. 3 shows a typical helical coil, which can bewound with the low-expansive side inside or outside, andright-hand or left-hand, mounted on the specimen holder.4. Summary of Test Method4.1 The test for thermal def l ection rate of spiral and helicalcoils consists of measuring the angular rotation that a coilundergoes in response to a known temperature change.5. Signif i cance and Use5.1 This test method simulates, to a practical degree, theoperation of the thermostat metal coil.5.2 The thermal def l ection properties of a coil may varyfrom lot-to-lot of thermostat metal material. This method isuseful for determining the optimum thickness and length of thematerial for a given def l ection specif i cation.5.3 This method is useful as a quality test to determineacceptance or rejection of a lot of thermostat metal coils.6. Apparatus6.1 Temperature Bath—A stirred liquid bath or uniformlyheated enclosure in which the specimen and mounting f i xturecan be placed shall be used. An adjustable heating source isdesirable for maintaining the specimen at the desired tempera-tures with a variation in temperature throughout the specimennot to exceed 0.5°F (0.3°C).6.2 Protractor—The angular position at each test tempera-ture shall be measured by a protractor with a minimum divisionof 0.5°.6.3 Temperature-Measuring Apparatus—The apparatus formaking temperature measurements shall be of such accuracythat the individual temperatures shall be known to be within60.5°F (60.3°C).1 This test method is under the jurisdiction of ASTM Committee B02 onNonferrous Metals and Alloys and is the direct responsibility of SubcommitteeB02.10 on Thermostat Metals and Electrical Resistance Heating Materials.Current edition approved Nov. 1, 2008. Published November 2008. Originallyapproved in 1962. Last previous edition approved in 2004 as B389 – 81 (2004).DOI: 10.1520/B0389-81R08.2 For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at service@astm.org. For Annual Book of ASTMStandards volume information, refer to the standard’s Document Summary page onthe ASTM website.Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1