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The THW technique is an absolute technique..

The errors that enter the technique are:

i. Recording of time:  ±  1 μs  or   10-3 %
ii. Voltage applied:  ±  1 μV  or   10-4 %
iii. Temperature:  ±10 mK  or  negligible
iv. Other parameters    0.05%
v. Resolution of FEM:  0.5% for the thermal conductivity

Therefore the absolute uncertainty of the technique, as applied for solids, is  (ISO-GUM  2008) :

1% for the thermal conductivity

5%  for the product (density x heat capacity)


Assael M.J., Antoniadis K.D., Kakosimos K.E., “An Improved Application of the Transient Hot-Wire Technique for the Absolute Accurate Measurement of the Thermal Conductivity of Pyroceram up to 420 K”, Int. J. Thermophys. 29:445-456 (2008).
Assael M.J., Antoniadis K., and Wu J., “New Measurements of the Thermal Conductivity of PMMA, BK7 and Pyrex 7740 up to 450 K”, Int. J. Thermophys. 29:1257-1266 (2008).