Viking DMOC205SS Absolute Humidity Sensor Circuit, Structure of Absolute Humidity Sensor

Models: VMOC205SS DMOC205SS

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DMOC205SS

VMOC205SS

ABSOLUTE HUMIDITY SENSOR CIRCUIT

(1)Structure of Absolute Humidity Sensor

The absolute humidity sensor includes two thermistors as shown in the illustration. One thermistor is housed in the closed vessel filled with dry air while another in the open vessel. Each sensor is provided with the protective cover made of metal mesh to be protected from the external airflow.

 

 

Sensing part

Sensing part

 

Sensing part

(Open vessel)

(Closed vessel)

 

 

 

 

(Open vessel)

Thermistor

Thermistor

Ventilation

 

element

element

openings

Sensing part

 

Sensor

 

(Closed vessel)

 

case

View of sensor case removed

Cross section view

 

(2)Operational Principle of Absolute Humidity Sensor The figure below shows the basic structure of an absolute humidity sensor. A bridge circuit is formed by two thermistors and two resistors (R1 and R2).

The output of the bridge circuit is to be amplified by the operational amplifier.

Each thermistor is supplied with a current to keep it heated at about 150οC (302οF), the resultant heat is dissipated in the air and if the two thermistors are placed in different humidity conditions they show different degrees of heat conductivity leading to a potential difference between them causing an output voltage from the bridge circuit, the intensity of which is increased as the absolute humidity of the air increases. Since the output is very minute, it is amplified by the operational amplifier.

 

 

 

 

Absolute humidity vs,

C

R1

Operational

output voltage characterist

amplifier

ge

 

 

 

Output

 

 

 

volta

 

 

+

voltage

 

 

 

 

 

-

 

Output

S

R2

 

S : Thermistor

R3

 

 

open vessel

 

 

 

C : Thermistor

 

 

 

 

closed vessel

 

 

 

 

 

Absolute humidity (g/m 2 )

(3)Detector Circuit of Absolute Humidity Sensor Circuit This detector circuit is used to detect the output voltage of the absolute humidity circuit to allow the LSI to control sensor cooking of the unit. When the unit is set in the sensor cooking mode, 16 seconds clearing cycle occurs

than the detector circuit starts to function and the LSI observes the initial voltage available at its AN6 terminal. With this voltage given, the switches SW1 to SW5 in the LSI are turned on in such a way as to change the resistance values in parallel with R50-1. Changing the resistance values results in that there is the same potential at both F-3 terminal of the absolute humidity sensor and AN7 terminal of the LSI. The voltage of AN6 terminal will indicate about -2.5V. This initial balancing is set up about 16 seconds after the unit is put in the Sensor Cooking mode. As the sensor cooking proceeds, the food is heated to generate moisture by which the resistance balance of the bridge circuit is deviated to increase the voltage available at AN6 terminal of the LSI. Then the LSI observes that voltage at AN6 terminal and compares it with its initial value, and when the comparison rate reaches the preset value (fixed for each menu to be cooked), the LSI causes the unit to stop sensor cooking; thereafter, the unit goes in the next operation automatically.

When the LSI starts to detect the initial voltage at AN6 terminal 16 seconds after the unit has been put in the Sensor Cooking mode, if it is not possible to balance, of the bridge circuit due to disconnection of the absolute humidity sensor, ERROR will appear on the display and the cooking is stopped.

1) Absolute humidity sensor circuit

 

IC2(IZA495DR)

 

 

SW1

 

 

4

64

 

 

P30

 

620k

 

 

 

5

63

SW2

 

 

P31

 

300k

 

 

 

6

62

SW3

 

 

P32

 

150k

 

 

 

7

61

SW4

 

75k

 

 

P33

C. Thermistor in

8

60

SW5

37.4k

 

 

P34

closed vesssl

 

 

 

S. Thermistor in

 

 

 

 

open vessel

 

3

5

 

F-1

11

 

47k

0.01µF

0.015µF

0.01µF

AN7

 

LSI

 

 

 

 

 

 

 

C

 

 

 

 

 

 

(IC1)

 

 

 

 

 

 

 

F-3

3.57k

 

+

 

10k

 

 

 

 

 

2

6

 

 

 

 

S

 

 

0.1 µF

 

 

47k

AN6

3.32k

-

 

 

 

F-2

1.8k

 

 

 

 

10

 

 

360k

 

 

 

 

 

 

 

 

 

 

R51

9

 

 

 

 

 

 

 

12

 

1

 

 

 

 

 

 

 

VA : -15V

 

VA : -15V

VC : -5V

 

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Viking DMOC205SS, VMOC205SS service manual Absolute Humidity Sensor Circuit, Structure of Absolute Humidity Sensor

VMOC205SS, DMOC205SS specifications

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In summary, the Viking DMOC205SS and VMOC205SS are exceptional microwave ovens that combine advanced technology, practical features, and stylish design. Their powerful cooking capabilities, user-friendly controls, and energy-efficient operation make them a perfect addition to any modern kitchen. These appliances empower users to explore a wide range of cooking possibilities, bringing convenience and quality to meal preparation.