Precision ovens for thermal endurance evaluation of electrical insulating material

It is shown how a commercially available oven can be easily modified by means of an iso-box to arrive at a temperature variation of /spl plusmn/ 1 K for thermal endurance evaluations. The modified oven meets all requirements as, for instance, given in IEC 216-4-1 or DIN 50 011, Part 12 with respect to construction and air flow. The temperature fluctuation in particular does not exceed /spl plusmn/ 0,5 K and a temperature gradient inside the iso-box may be neglected. It is also shown that, in case of twisted pairs, the uncertainty of measurement of the temperature that corresponds to the temperature index can be reduced to /spl plusmn/ 4 K.