Haven't You Calibrated Your Microwave Oven Yet?

Abstract

With radiation of 2.46 GHz, the magnetron tube of any microwave oven (MWO) has an energy output equivalent to 0.2388 cal. S⁻¹.w⁻¹ that enables an accurate calorimetric calibration by heating 1 kg distilled water (DW) for exactly 120 seconds. The manufacturer's power rating of any MWO cannot be taken as correct, neither can the energy output of the 10 different power levels that any MWO is supposed to be able to provide. The calibration should include the energy output at every power level, as well as calibration curves of different water masses heated for different periods of time. There are differences in the final temperature of reagents with or without slides, but there are no differences to the final temperature of DW versus aqueous solutions. Alcoholic solutions have to be treated differently to avoid boiling. With the same technology in use in all designs of MWOs, and because of their wide spread use, it is proposed that the accreditation requirements for histology laboratories include MWO calibration. (The J Histotechnol 25:39, 2002)

Submitted: August 23, 2001; Accepted with revisions: December 7, 2001

Keywords:

• calorimetric calibration
• laboratory accreditation
• magnetron tube