Diesel Flow Meter | DN25 Oval Gear Electronic Gauge | Fuel Dispenser Counter

This 1-inch inline meter measures liquid volume as fluid passes through its internal chamber. Two interlocking oval gears turn with the flow to track exact volume per rotation. The meter reads thin fuels, heavy 50-weight gear oils, and urea without drifting off calibration. Features and Benefits - Positive displacement oval gears - Hold measurement error within 0.5% without requiring long straight pipe runs on either side - Digital LCD screen - Shows a five-digit resettable batch count and an eight-digit permanent lifetime total - DN25 female inlet and outlet - Threads directly onto standard 1-inch pipe fittings and handles flow rates up to 120 liters per minute - Quantitative control wire output - Sends a cutoff signal to an external solenoid valve once your chosen volume is reached Applications - Tracking fuel output on commercial diesel pumping skids and bulk dispensing tanks - Metering DEF and urea transfers through stainless-compatible systems without corrosion buildup - Dispensing exact fluid batches from mobile lube trucks running hydraulic and transmission oils Safety & Materials Fit this unit only into lines carrying diesel, petrol, or urea. The DN25 25 mm inlet and outlet threads require correct fuel-rated sealant or PTFE tape to prevent fluid leaks under line pressure. Unlike a standard turbine sensor that relies on fluid velocity, the internal oval gear positive displacement design handles heavy fuels without slipping. Ground the metal housing and pipework to dissipate static charges, especially when pumping petrol. Isolate all DC power sources before opening the electronic digital display housing, and ensure all seals sit cleanly in their recesses during reassembly to keep moisture away from internal circuitry. Core Parts Needed: To build a monitored dispensing setup or understand how to make a fuel flow meter rig, gather these essential components: - Diesel flow meter with DN25 25 mm threaded connections - 1-inch fuel delivery hose rated for petroleum products - Fuel transfer pump delivering within the 10-100 L/min range - Automatic shut-off delivery nozzle with internal venturi port - Microcontroller board such as an Arduino running on 5V logic - Regulated 12V DC power supply for pumping operations - Pulse pickup sensor or digital interface cable - Stainless steel hose clamps and brass thread adaptors Hardware Connection & Schematic Plumb the 25 mm ports directly in line between your transfer pump and delivery hose. Downstream, fit an automatic shut-off nozzle. When asking how does a fuel nozzle shut off, the mechanism uses a venturi tube near the spout tip; rising fuel blocks the air passage, creating a vacuum that trips the mechanical shut-off spring. For external telemetry, connect the meter pickup sensor ground to the microcontroller ground pin. Route the signal wire to digital interrupt pin 2 on the board. Power the microcontroller with a regulated 5V supply, keeping it separate from the noisy 12V pump motor feed. Calibration & Math Understanding how fuel flow meter works relies on positive displacement. Inside the chamber, fluid pressure forces two meshed oval gears to rotate, sweeping a fixed fluid volume per rotation. The meter operates across a 10-100 L/min window. To calibrate external logging, divide the total pulses counted by the volume dispensed. If a 20-litre test dispense yields 800 pulses, your flow factor is 40 pulses per litre. Calculate instantaneous flow by measuring pulses over time: multiply the pulse count per second by 60, then divide by the calibration factor to display litres per minute on the electronic digital register. Arduino Code Example Use this interrupt script to read pulses from the flow sensor: volatile unsigned long pulseCount = 0; float calibrationFactor = 40.0; unsigned long lastTime = 0; void countPulse() { pulseCount++; } void setup() { Serial.begin(9600); pinMode(2, INPUTPULLUP); attachInterrupt(digitalPinToInterrupt(2), countPulse, FALLING); } void loop() { if (millis() - lastTime >= 1000) { detachInterrupt(digitalPinToInterrupt(2)); float flowRate = (pulseCount / calibrationFactor) 60.0; Serial.print("Flow: "); Serial.print(flowRate); Serial.println(" L/min"); pulseCount = 0; lastTime = millis(); attachInterrupt(digitalPinToInterrupt(2), countPulse, FALLING); } }