Sharp R-320BB Service Manual page 9

enough steam from the food, it relays the information to its
microprocessor which will calculate the remaining cooking
time and power level needed for best results. When the food
is cooked, water vapor is developed. The sensor "senses"
the vapor and its resistance increases gradually. When the
resistance reaches the value set according to the menu,
supplementary cooking is started.
The time of supplementary cooking is determined by experi-
ment with each food category and inputted into the LSI.
An example of how sensor works: (POTATOES)
1. Potates at room temperature. Vapor is emitted very
slowly.
2. Heat Potates. Moisture and humidity is emitted rapidly.
You can smell the aroma as it cooks.
AH SENSOR
SCHEMATIC
NOTE: CONDITION OF OVEN
1. DOOR CLOSED
2. CLOCK APPEARS ON DISPLAY
GRN
120V AC
60 Hz
THERMAL
MONITOR THERMAL
CUT-OUT (OVEN)
FUSE 20A CUT-OUT (MG.)
A2
(RY-1)
A1
CONTROL UNIT
N.O.
TTM
OL FM
TURN-
OVEN
FAN
TABLE
LAMP
MOTOR
MOTOR
SECONDARY
INTERLOCK
SWITCH
Figure O-1. Oven Schematic-Off Condition
3. Sensor detects moisture and humidity and calculates
cooking time and variable power.
Cooking Sequence.
1. Touch one of the SENSOR pads.
NOTE: The oven should not be operated on SENSOR
immediately after plugging in the unit. Wait two
minutes before cooking on SENSOR.
2. The coil of shut-off relay (RY-1) is energized, the turntable
motor, oven lamp and cooling fan motor are turned on,
but the power transformer is not turned on.
3. After about 16 seconds, the cook relay (RY-2) is
energized. The power transformer is turned on,
microwave energy is produced and first stage is started.
The 16 seconds is the cooling time required to remove
any vapor from the oven cavity and sensor.
NOTE: During this first stage, do not open the door or touch
STOP/CLEAR pad.
4. When the sensor detects the vapor emitted from the
food, the display switches over to the remaining cooking
time and the timer counts down to zero.
At this time, the door may be opened to stir, turn, or
season food.
5. When the timer reaches zero, an audible signal sounds.
The shut-off relay and cook relay are de-energized and
the power transformer, oven lamp, etc. are turned off.
6. Opening the door or touching the STOP/CLEAR pad, the
time of day will reappear on the display and the oven will
revert to an OFF condition.
COM.
N.O.
(RY-2)
PRIMARY
INTERLOCK
RELAY
COM.
SH-B SH-A
DOOR
SENSING
MONITOR
SWITCH
SWITCH
7
R-320BB
R-320BK
R-320BW
POWER
TRANSFORMER
RECTIFIER
MAGNETRON