20
MEASUREMENT AND TEST
1. MEASUREMENT OF THE MICROWAVE POWER OUTPUT
Microwave output power can be checked by indirectly measuring the temperature rise of a certain amount of water
exposed to the microwave as directed below.
PROCEDURE
1. A cylindrical container of borosilicate glass is used for the test. It has a maximum thickness of 3mm, an external
diameter of approximately 190mm and a height of approximately 90mm.
The mass of the container is determined.
2. At the start of the test, the oven and the empty container are at ambient temperature. Water having an initial
temperature of 10˚C ± 1˚C is used for the test. The water temperature is measured immediately before it is poured
into the container.
3. A quantity of 1000g ± 5g of water is added to the container and its actual mass obtained.
The container is then immediately placed in the centre of the oven shelf, which is in its lowest normal position.
The oven is operated and the time for the water
temperature to attain 20˚C ± 2˚C is measured. The oven
is then switched off and the final water temperature is
measured within 60s.
NOTE 1 - The water stirred is before its temperature is
measured.
NOTE 2 - Stirring and measuring devices are to have a
low heat capacity.
4. The microwave power output is calculated from the
formula
where
P
is the microwave power output, in watts ;
m
w
is the mass of the water, in grams ;
m
c
is the mass of the container, in grams ;
T
0
is ambient temperature, in degrees Celsius ;
T
1
is the initial temperature of the water, in degree Celsius ;
T
2
is the final temperature of the water, in degrees Celsius ;
t
is the heating time, in seconds, excluding the magnetron filament heating-up time.
✻
The microwave power output is stated in watts, rounded off to the nearest 50W
✻
Heating time for power output: (T
2
= T
0
)
CAUTION
1. Water load should be measured exactly to 1 liter.
2. Input power voltage should be exactly specified voltage (Refer to 2. SPECIFICATIONS).
3. Ambient temperature should be 20 ± 2°C (68 ± 3.6°F)
P = 4,187 •
T
2
- T
1
)/t + 0.55 • mc T
2
- T
0
)/t
70
600
64
650
60
700
56
750
52
800
49
850
47
900
44
950
42
1000
40
1050
38
1100
A (second)
B (W)
