ASTM B84-07(R2019) pdf free download

ASTM B84-07(R2019) pdf free download.Standard Test Method for Temperature-Resistance Constants of Alloy Wires for Precision Resistors
1. Scope
1.1 This test method covers determination of the change of resistance with temperature of alloy wires used for resistance standards and precision resistors for electrical apparatus. 1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.3 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 appro- priate safety, health, and environmental practices and deter- mine the applicability ofregulatory limitations prior to use. 1.4 This international standard was developed in accor- dance with internationally recognized principles on standard- ization established in the Decision on Principles for the Development of International Standards, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Significance and Use
2.1 Procedure A covers the determination of the equation of the curve relating resistance and temperature where the curve approximates a parabola. This test method may be used for wire of any metal or alloy over the temperature interval appropriate to the material. 2.2 Procedure B covers the determination of the mean temperature coefficient of resistance for wire of any metal or alloy over the temperature interval appropriate to the material.
3. Apparatus
3.1 The apparatus for making the test shall consist of one or more baths for maintaining the specimen at the desired temperatures; thermometers for measuring the temperatures of the baths; and suitable means for measuring the resistance of the specimen. Details of the apparatus are given in Sections 4 to 6.
4. Baths
4.1 Baths for use from −65 to +15 °C may consist of toluol, or equivalent. 4.2 Baths for use above 15 to 250 °C may consist of chemically neutral oils with a low viscosity, having a flash point at least 50 °C higher than the temperature of use. 4.3 The liquid in these baths shall be ofsuch quantity and so well stirred that the temperature in the region occupied by the specimen and the thermometer will be uniform within 0.5 °C for any temperature between −65 and +100 °C, and within 1.0 °C for any temperature above 100 to 250 °C. If the temperature range is less than 100 °C, the uniformity of temperature shall be proportionately closer. N OTE 1—It is recommended that a solvent bath at room temperature shall be used to rinse specimens before immersion in any temperature bath.
5. Temperature Measurement Apparatus
5.1 The temperature shall be measured to an accuracy of 60.5 °C, or 1 % of temperature range, whichever is smaller.
6. Resistance Measurement Apparatus
6.1 The change of resistance of the specimen shall be measured by apparatus capable of determining such changes to 0.001 % of the resistance of the specimen if the temperature range is 50 °C or more. If the temperature range is less than 50 °C, the accuracy of the resistance change measurements shall be correspondingly greater. 6.2 The connections from the specimen to the measuring device shall be such that changes in the resistance of these connections due to changes in their temperature do not appreciably affect the measurement of the change in resistance of the specimen. 6.3 The temperature of the measuring apparatus shall not change during the test by an amount sufficient to introduce appreciable errors in the results. With apparatus of good quality, a change in 1 °C in room temperature is allowable.