Electrolux # Посібник з експлуатації - Сторінка 32

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GLMV169GSB

GLMV169GBB

GLMV169GQB

PLMVZ169GCB/C

(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.

ventilation opening for sensing

(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 150

C (302

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.

Operational

amplifier

Output

voltage

S : Thermistor

open vessel

C : Thermistor

closed vessel

(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 AN1 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 R98 ~ R102 of IC2.

Changing the resistance values results in that there is the

same potential at both F-3 terminal of the absolute humidity

sensor and AN0 terminal of the LSI. The voltage of AN1

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

ABSOLUTE HUMIDITY SENSOR CIRCUIT

Thermistors

Sensing part

(Open vessel)

(Closed vessel)

F), the resultant heat is

Absolute humidity vs,

output voltage characteristic

Absolute humidity (g/m )

balance the bridge circuit is deviated to increase the

voltage available at AN1 terminal of the LSI.

Then the LSI observes that voltage at AN1 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 AN1

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

R98

R99

R100

R101

R102

C. Thermistor in

closed vessel

S. Thermistor in

open vessel

R97

47k

F-1

R96

F-3

3.57k

R91

R92

3.32k

F-2

1.8k

VA : -15V

SW1

620k

P33

SW2

300k

P34

SW3

150k

P35

SW4

75k

P36

37.4k

SW5

P37

AN0

LSI

(IC1)

R94

R95

IC2

AN1

10k

47k

R93

360k

D90

VC : -5V