Flow Meter Gun | Digital Auto Shut-Off Nozzle | Fuel Dispensing Gun

This fuel nozzle measures liquid output directly as you pump, using an internal turbine and digital display. Housed in cast aluminum, it connects straight to your delivery hose so you can read batch amounts and overall totals right at the tank opening. Features and Benefits - Integrated digital turbine meter - Tracks output within 1 percent accuracy so you can balance tank ledgers - Clear LCD display with reset button - Toggles between gallons, liters, pints, and quarts to show exact volumes - Standard 1-inch NPT threaded inlet - Screws right onto standard farm tanks, gravity lines, and electric pump hoses - Replaceable internal battery power - Runs about two years on a single battery set without running extra cords Applications - Logging diesel or kerosene volume pumped into fleet vehicles, mowers, and farm machinery - Tracking fuel dispensed from mobile jobsite trailers into field equipment - Metering light machine oils and non-corrosive workshop lubricants during equipment servicing Safety & Materials This fuel dispensing gun uses an aluminium body engineered for hard workshop use when handling diesel, fuel, and oil. Aluminium gives the casting structural strength without adding dead weight during long transfers, whilst resisting corrosion from petroleum-based fluids. Always earth your transfer setup to prevent static buildup around fuel vapours. Inspect the battery compartment seal regularly to stop oil creeping into the electronic digital display housing. Never use this unit with petrol, water, or corrosive chemicals unless the fluid compatibility explicitly permits it. Wipe the nozzle clean after every use to stop grit entering vehicle filler necks. Core Parts Needed: To understand how to make a fuel flow meter or service this assembly, you need standard shop hardware: - Robust aluminium dispensing nozzle body with internal shut-off mechanism - Electronic digital register assembly with replaceable internal battery - In-line turbine sensor with a magnetic pickup sensor - Fuel-rated delivery hose with threaded swivel inlet fitting - Thread sealant resistant to diesel and hydrocarbon oils - Viton or nitrile rubber internal sealing O-rings - Stainless steel hardware and protective terminal caps Hardware Connection & Schematic Fluid enters through the threaded inlet and passes directly across an internal turbine sensor. As fluid pushes the turbine blades, an embedded magnet passes a pickup sensor, converting fluid velocity into discrete electrical pulses. The electronic digital meter reads these signals to calculate volume. Mechanics wondering how a fuel nozzle shuts off should note the mechanical venturi port near the spout tip. As fuel fills the tank and covers this small sensing hole, the change in air pressure collapses an internal diaphragm, mechanically tripping the main valve poppet to instantly cut the flow, independent of the digital display. Calibration & Math Understanding how fuel flow meter systems work requires basic pulse math. Each revolution of the turbine sensor generates a specific pulse count per litre, often referred to as the K-factor. To calculate dispensed volume, divide total incoming pulses by this calibration factor: Volume (Litres) = Pulses / K-factor. If a bench test reveals the meter reads 19.5 litres into a verified 20-litre proving tank, adjust the calibration value in your electronics. Calculate the error percentage, then alter the internal factor: New K-factor = Old K-factor x (Metered Volume / Actual Volume). Repeat this until dispensed volume matches your vessel. Arduino Code Example Building a custom test rig flow sensor readout requires reading digital pulses via an interrupt pin. Connect the pickup sensor signal wire to digital pin 2 with a 10k pull-up resistor to the 5V rail. Ground the sensor to the microcontroller ground: volatile unsigned long pulseCount = 0; const float kFactor = 450.0; void setup() { Serial.begin(9600); pinMode(2, INPUTPULLUP); attachInterrupt(digitalPinToInterrupt(2), addPulse, FALLING); } void loop() { static unsigned long lastCheck = 0; if (millis() - lastCheck >= 1000) { lastCheck = millis(); float totalLitres = pulseCount / kFactor; Serial.println(totalLitres); } } void addPulse() { pulseCount++; }