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8. PROCEDURE FOR MEASURING MICROWAVE
ENERGY LEAKAGE
A. CAUTIONS
(1) Be sure to check a microwave emission prior to
servicing the oven if the oven is operative prior to
servicing.
(2) The service personnel should inform the manufacturer,
importer, or assembler of any certified oven unit found
to have a microwave emission level in excess of
5mW/cm.sq. and should repair any unit found to have
excessive emission levels at no cost to the owner and
should ascertain the cause of the excessive leakage.
The service personnel should instruct the owner not to
use the unit until the oven has been brought into
compliance.
(3) If the oven operates with the door open, the service
personnel should;
- Tell the user not to operate the oven
- Contact the manufacturer and CDRH (Center for
Devices and Radiological Health) immediately.
NOTE: Address on CDRH
Office of Compliance (HFZ-312)
Center for Devices and Radiological Health
1390 Piccard Drive Rockville, Maryland 20850
(4) The service personnel should check all surface and
vent openings for microwave emission testing.
(5) Check for microwave energy leakage after every
servicing. The power density of the microwave radiation
leakage emitted by the microwave oven should not
exceed 1mW/cm.sq. And always start measuring of an
unknown field to assure safety for operating personnel
from radiation leakage.
NOTE: The standard is 5mW/cm.sq. while in the
customer’s home. 1mW/cm.sq. stated here is
manufacturer’s own voluntary standard for units in
customer’s home.
EQUIPMENT
Electromagnetic energy leakage monitor (NARDA
8100B, HOLADAY HI 1501)
600cc glass beaker
Glass thermometer 100
0
C
B. MEASURING MICROWAVE ENERGY LEAKAGE
(1) Pour 275
15cc of 20 5 ˚C water in a beaker which is
graduated to 600 cc, and place the beaker in the center
of the oven.
(2) Set the energy leakage monitor to 2,450 MHz and use it
following the manufacturer’s recommended test
procedure to assure correct result.
(3) When measuring the leakage, always use the 2 inch
(5 cm) spacer supplied with the probe.
(4) Operate the oven at its maximum output.
(5) Measure the microwave radiation using and
electromagnetic radiation monitor by holding the probe
perpendicular to the surface being
measured. (See Figure 7)
C. MEASUREMENT WITH THE OUT CASE REMOVED
(1) When you replace the magnetron, measure for
microwave energy leakage before the outer case is
installed and after all necessary components are
replaced or adjusted. Special care should be taken in
measuring the following parts.
- Around the magnetron
- The waveguide
WARNING: AVOID CONTACTING ANY HIGH VOLTAGE
PARTS.
-12-
Move probe along shaded area.
Probe scanning speed
less than 2.5 cm/sec.
Figure 7
Figure 6