GE PDE9900 manual Test, Calibrating the Turbidity Sensor

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Turbidity Sensor

The turbidity sensor is located on the side of the sump.

Turbidity Sensor

The turbidity sensor measures the amount of suspended particles in the wash water in the sump. The control sends the turbidity sensor a pulse width modulated 5-volt signal for calibration and usage during operation.

The control then receives an analog signal of the sensed turbidity, which is processed by the microprocessor.

The baseline reading is taken during the first fill when the sump water level is between the 1/4- to 3/8-in. gap between the LED transmitter and the receptor. Successive turbidity measurements are supplied to the control module and used to determine whether any prewash or rinse cycles can be skipped. The sensing LED is on during all prewash cycles and during the final rinse.

Decisions are based on a comparison of clean water measurements at the beginning of the first fill, measurements taken at selected fills, and water temperature. By measuring the turbidity level, the control module can conserve energy on lightly soiled loads by skipping unnecessary cycles.

Note: If the turbidity sensor circuit fails to open or is shorted, the sensing LED on the control panel will not light, and the unit will operate for the maximum amount of time, using the maximum number of wash and rinse fills for the selected cycle.

The turbidity sensor also contains the thermistor for automatic temperature controlTurbidity Sensor

Test

The thermistor’s resistance has a negative temperature coefficient. As the temperature increases, the resistance goes down. At 75°F, the resistance is approximately 9.9K Ω. At 140°F, the resistance is approximately 2.8K Ω.

Note: When installing the turbidity sensor, align the key on the sensor with the keyway on the sump.

Key

The Service Mode is the most accurate way to test the turbidity sensor circuit. The turbidity sensor circuit contains the control module, wiring, and the turbidity sensor.

Turbidity Sensor Strip Circuit

YELLOW/BLK

NTC

1

DK. BLUE

2

GRAY

3

ORANGE

4

 

Calibrating the Turbidity Sensor

When replacing the turbidity sensor, or if it has been disconnected, always calibrate the turbidity sensor to the control board.

Note: The calibration cycle MUST be entered within 2 minutes of power up.

Press the Normal pad (the up arrow pad on Top Control Models) and the Cookware pad (the down arrow pad on Top Control Models) for 3 seconds or until all LEDs turn on.

The dishwasher will then perform a series of steps. Once the drain cycle starts, calibration is complete and the Start/Reset pad can be pressed to end the calibration cycle. The dishwasher will continue to pump out remaining water and cycle of.

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Contents Technical Service Guide Important Safety Notice Table of Contents Serial Number NomenclatureW 9 9 8 0 L 0 0 S S Model NumberIntroduction PDW8900 Series Control FeaturesSelections Enhancements Start PDW8900 Series Shown Door View Component Locator ViewsPDW8900 Series Shown Inside Cabinet View Left Side ViewRear of Dishwasher PDW9000 Series ShownPDW8900 Series Shown Bottom View Front of DishwasherPDW8900 Series Dishwasher ComponentsDoor Panel PDW9700 Series and PDW9900 Series Keypad Assembly PDW9700 Series and PDW9900 Series Front Mount Control PDW8900 Water Hardness Test and Calibration Test Water HardnessSmartDispenseTM Calibration Water Hardness Test Strip IndicationTo remove the reservoir SmartDispenseTMDetergent Reservoir Detergent Level Sensor To remove the pump Positive Displacement PumpApproximate Detergent Use Consumer Purge Cycle When to Purge the Bulk Dispenser TankCustomer Purge of the Bulk Dispenser Tank first time the module is activated Door Interlock SwitchDetergent/Rinse Module Middle Spray Arm Using the Dishwasher with the Upper Rack Removed Removal and Replacement Lower Spray Arm, Fine Filter, and Inlet Cover Upper Spray ArmMain Conduit Fill FunnelHeating Element Calibrating the Turbidity Sensor Turbidity SensorTest Drain System Smart Fill System Water Valve Test Water Valve and Flood SwitchWash Cycles Demo ModeControl Module Board Control ModuleActive Vent Normal Wash Cycle Single Rack WashTMWax Motor and Magnet Circulation Pump and MotorDoor Spring Installation Description Time Service ModeEntering Factory Test Mode Factory Test ModeVerify operation after Schematics and Strip CircuitsPDW9900 Series PDW9700 SeriesFor The Period GE Will Replace Warranty for 2005 ProductFor The Period GE Will Replace Warranty for 2006 and Later Product
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