16
R-244M -
MICROWAVE MEASUREMENT
After any repair, the microwave oven must be checked for microwave leakage to ensure continued safe operation. BS EN 60335-
2-25 specifies that the maximum permitted leakage with a load of 275 ml is 50 W/m
2
(equivalent to 5 mW/cm
2)
at a distance of
5 cm from the oven.
PREPARATION
The following items are required to carry out this test:-
1. A low form of 600 ml beaker made from an electrically non-conductive material, such as glass or plastic, with an inside
diameter of approximately 8.5 cm. This must contain 275
±
15 ml of water, at an initial temperature of 20
±
2˚C.
2. A leakage detector which has been calibrated within the preceding 12 months to a standard whose accuracy can be traced
to National Physical Laboratory Standards.
Recommended instruments are:
Apollo “XI”
Celtec “A100”
Before commencing the test, check that the leakage detector is functioning and adjusted according to the manufacturer’s
instructions, and any spacers are fitted to ensure that measurement is taken 5cm from the surface of the oven.
PROCEDURE
1. Place the beaker containing the water load in the oven cavity at the centre of the turntable. The placing of this standard load
in the oven is important, not only to protect the oven, but also to ensure that any leakage it is not disguised by too large a
load absorbing energy.
2. Close the oven door, and with the power level set to FULL, turn the oven ON with the timer set for a few minutes operation.
Should the water begin to boil before the test has been completed, it should be replaced.
3. As shown in the diagram below, move the probe slowly (not faster than 2.5 cm/sec.);-
a) around the edge of the door following the gap
b) across the face of the door
c) across any vents in the oven’s sides, rear or top
Dotted line indicates the path by the leakage detector.
Whilst the maximum leakage permitted in BS60335 2-25 is 50 /W/m
2
(equivalent to 5 W/cm
2
),it is not normal to detect any
significant leakage, and therefore any detected leakage should be investigated.
