Bennett 3000 Series Service Manual page 27

System Operation - Overview
High Flow Meter and Pulser - The high flow meter / pulser are contained in a single unit. You cannot
replace one without the other. They are contained in a single housing. This meter is referred to as the
High Flow meter and is used in the "Little Squirt" and "Big Squirt" dispensers for higher flow rates. This
meter / pulser assembly is electronically calibrated in the field using the e-cal switch on the CPU board.
Refer to the Operators portion of this manual for further details.
Handle Switch - The handle switch allow the system to know when the customer wants to dispense
fuel and signals the CPU to turn on the pump motor. The handle switch uses a "reed" style proximity
switch and magnet to signal when the nozzle has been removed from the boot. In the nozzle boot there
is a lift lever . Attached to this is a magnetic pickup. When the lift lever is raised, the magnet moves in
proximity to a reed switch on the handle circuit board. When this happens, the reed switch is pulled in
completing the circuit. This circuit is electrically "Open" when the nozzle is in the boot, and it is
electrically "Closed" when the lever is lifted. The CPU knows that the handle has been lifted when it sees
it go from open to closed. The CPU then sends a +12 volt dc signal to a relay to turn on the motor. When
the handle is returned to the nozzle boot the CPU turns off the pump motor and signals that the sale is
complete and the CPU sends this information to the Point of Sale device (or Fleet system if there is
one).
Valve control - The dispenser may or may not have a valve/s, depending on which model has been
ordered. If there is, the CPU also controls the valve. The hose will have a 2 stage valve. The valve is
there to control product flowing through a hose. It prevents the unauthorized dispensing from a hose that
isn't authorized. It is also used to slow down the flow towards the end of a pre-pay or preset sale. The 2
stage valve operates off +24 volts dc. If the system uses a valve, there is one valve on the output of
every meter.
Note - For the Satellite unit in a Master / Satellite High flow system, the satellite valve operates off of
120 volts. However, the valve in the Master operates off of +24volts D.C.
2 Stage Valve Control (Theory) - On a two stage valve, there are 2 "stages", slow flow and fast flow.
When the handle is lifted the CPU should turn on the motor and turn on the valve. At the beginning of
the fuel transaction, as previously mentioned, the slow flow portion of the valve opens first for the
product and the CPU starts counting pulses. It only opens the slow flow portion of the valve at first after
the handle is lifted and the dispenser is authorized. After 9 good pulses are received from each phase of
the pulser it will open up the valve to the "fast" flow. The CPU does this by controlling the coils of the
solenoid of the 2 stage valve. It does this by providing the coils with a path to ground through a field
effect transistor (FET) on the CPU. The valve has 3 wires coming out of it, red, yellow and black. The
red is +24 volts, the yellow controls the slow flow coil and the black controls the fast flow coil.
System memory - All programming information is stored in non-volatile RAM and will not be lost if
dispenser power is lost. Also, an E2ROM chip holds electronic calibration and electronic totals and WILL
NOT BE LOST with a RAM clear procedure.
System software - The CPU "operating program" is provided by use of a micro - controller. This
EPROM determines the functions that are available on the dispenser.
The Main Display - The main display is used for the customer to view the volume amount of the sale. It
is also used to house the electromechanical totalizers. The display gets its information from the CPU.
The display is part of the CPU board.
Main Display Backlighting Board - The CPU does not use lights or ballasts. To light the display it
uses a backlight board using a series of 1.5 volt Light Emitting Diodes (LED's). By using this type of
lighting it eliminates the need to replace burnt out light bulbs and ballasts. These LED's are powered
from +24 volts it receives from the CPU.
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107932 Rev G 4-24-17