4.1 The use of heat flux transducers on building envelope components provides the user with a means for performing in-situ heat flux measurements. Accurate translation of the heat flux transducer output requires a complete understanding of the factors affecting its output, and a standardized method for determining the heat flux transducer sensitivity for the application of interest.

4.2 The sensitivity of the heat flux transducer is determined primarily by the sensor construction and temperature of operation and the details of the application, including geometry, material characteristics, and environmental factors.

4.3 The presence of a heat flux transducer is likely to alter the heat flux that is being measured. To determine the heat flow that would occur in the absence of the transducer, it is necessary to either:

4.3.1 Ensure that the installation is adequately guarded (1).³

4.3.2 Adjust the results based on a detailed model or numerical analysis. Such analysis is beyond the scope of this practice, but details can be found in (2-6).

4.3.3 Use the empirically measured heat flux transducer sensitivity measured under conditions that adequately simulate the conditions of use in the final application.

4.4 There are several methods for determining the sensitivity of heat flux transducers, including Test Methods C177, C518, C1114, and C1363. The selection of the appropriate procedure will depend on the required accuracy and the physical limitations of available equipment.

4.5 This practice describes techniques to establish uniform heat flow normal to the heat flux transducer for the determination of the heat flux transducer sensitivity.

4.6 The method of heat flux transducer application must be adequately simulated or duplicated when experimentally determining the heat flux transducer sensitivity. The two most widely used application techniques are to surface-mount the heat flux transducer or to embed the heat flux transducer in the insulation system.

1.1 This practice, in conjunction with Test Method C177, C518, C1114, or C1363, establishes an experimental procedure for determining the sensitivity of heat flux transducers that are relatively thin.

1.1.1 For the purpose of this standard, the thickness of the heat flux transducer shall be less than 30 % of the narrowest planar dimension of the heat flux transducer.

1.2 This practice discusses a method for determining the sensitivity of a heat flux transducer to one-dimensional heat flow normal to the surface and for determining the sensitivity of a heat flux transducer for an installed application.

1.3 This practice should be used in conjunction with Practice C1046 when performing in-situ measurements of heat flux on opaque building components.

1.4 This practice is not intended to determine the sensitivity of heat flux transducers that are components of heat flow meter apparatus, as in Test Method C518.

1.5 This practice is not intended to determine the sensitivity of heat flux transducers used for in-situ industrial applications that are covered in Practice C1041.

1.6 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.