Current position > Product detail
『Adafruit Liquid Flow Meter: Hall effect pulse sensor wiring and coding.』Related information(clamp on meter|electromagnetic meter|venturi meterrotameter|orifice meter|ultrasonic flow meter|mass flow meter|coriolis mass flow meter|coriolis flow meter|magnetic flow meter|magmeter flow meter|magflow flow meter|mag meter flow meter|electromagnetic flow meter|vortex flow meter|turbine flow meter|thermal mass flow meter|thermal flow meter|rotameter flow meter)
Adafruit Liquid Flow Meter: Hall Effect Pulse Sensor Wiring and Coding
Quick Answer: The Adafruit liquid flow meter has a Hall effect sensor that outputs a pulse train. Wire the red lead to 5 VDC, the black lead to GND, and the yellow lead to a digital input. For industrial flow above 10 L/min or aggressive fluids, you should look at a Silver Instruments industrial flow meter instead.
This guide covers wiring and coding for the Adafruit Hall effect pulse sensor. It also covers the limits of this device in real process plants. We sell industrial flow meters, but we still get asked about low cost sensors for bench tests and small dosing skids.
How the Hall Effect Sensor Works
The Adafruit liquid flow meter has a small plastic turbine inside the body. A magnet sits in the turbine hub. The Hall effect sensor in the housing detects each rotation. The sensor output is a square wave. Each pulse equals a fixed volume of liquid. The pulse frequency changes with flow rate.
Most Adafruit liquid flow meters operate on 5 VDC. The output is open collector NPN. You need a pull up resistor if your controller does not have an internal pull up. An Arduino Uno has an internal pull up on digital pins. A typical Adafruit meter has a range of 1 to 30 liters per minute. Accuracy is usually around plus or minus 10 percent. The fitting size is 1/2 inch NPT. This meter suits clean water testing or low viscosity coolant loops.
We have seen customers in Southeast Asia use this meter for small bench top test rigs. A laboratory in Vietnam used it to measure cooling water flow in a test chamber. It worked fine for that job.
Wiring the Pulse Sensor to an Arduino or PLC
Wiring is simple. The red wire connects to 5 VDC. The black wire connects to ground. The yellow wire connects to digital pin 2 on an Arduino. If you use a PLC, connect the yellow wire to a high speed counter input. Use a 10 kOhm pull up resistor from the yellow wire to 5 VDC if the PLC input does not have one.
Do not run the pulse cable next to VFD motor cables. Pulse signals lose strength and pick up noise in an industrial panel. We have seen this on customer sites many times. Use a shielded cable for cable runs over 2 meters. Ground the shield only at the PLC end.
Sample Code for Reading Flow Rate
The Arduino code counts pulses on interrupt 0. The code below reads the pulse count every one second. It converts frequency to liters per minute using a factor of 7.5 Hz per L/min. This factor is common for the Adafruit plastic flow meter.
volatile int pulseCount;
void pulseCounter() { pulseCount++; }
void setup() { pinMode(2, INPUT_PULLUP); attachInterrupt(digitalPinToInterrupt(2), pulseCounter, RISING); Serial.begin(9600); }
void loop() { if (millis() - lastTime >= 1000) { float frequency = pulseCount; float flowRate = frequency / 7.5; pulseCount = 0; lastTime = millis(); Serial.println(flowRate); delay(100); } }
Note that the variable lastTime must be declared as unsigned long lastTime. This code is for bench testing only. Do not use it f
Industrial Limits of the Adafruit Meter
The Adafruit liquid flow meter is a low cost device. It works for clean water, glycol, or low viscosity oils. It does not work well with slurries, seawater, hot condensate, or liquids above 60 degrees Celsius. The plastic body can crack at pressures above 0.5 MPa. The Hall effect sensor is not ATEX certified. Do not install this meter in Zone 1 or Zone 2 hazardous areas.
Here is the thing. We have seen customers use this meter for fuel oil in the Philippines. The diesel swelled the plastic and the turbine stopped after a week. A customer in a paint factory in Vietnam had the same issue. The paint caused the turbine to stick after two days. That customer replaced it with a Silver Instruments oval gear flow meter. The oval gear meter handles viscous paints and gives a 4 to 20 mA signal.
When to Move to a Silver Instruments Industrial Flow Meter
For pipe sizes DN15 and above, you can use a Silver Instruments electromagnetic flow meter. It has no moving parts and works with conductive liquids. For oils and solvents, a positive displacement flow meter is better. For gas or steam, use a vortex flow meter. If you need a seawater flow meter for a desalination plant, use an electromagnetic meter with PTFE liner and titanium electrodes.
Send us your pressure in bar, temperature in degrees Celsius, pipe size in DN, and flow range. We will recommend a meter with the right approval and liner material. Contact Silver Automation Instruments at Tel: +86-135-1213-1526, Whatsapp: 86-135-12131526, WeChat: +86 13512131526.
FAQ
Q1. Can the Adafruit liquid flow meter be used for seawater desalination?
No. The plastic body and Hall effect sensor are not rated for continuous seawater service. For desalination plants, use a Silver Instruments electromagnetic flow meter with PTFE liner and titanium electrodes.
Q2. What is the pulse output frequency range?
The common Adafruit meter outputs 0 to 300 Hz. At 30 L/min the frequency is around 225 Hz. Check the calibration factor on the product label. Different batches use different K factors.
Q3. How do I connect the pulse sensor to a PLC high speed counter?
Wire the yellow lead to the counter input. Set the counter mode to pulse or frequency. Use a 10 kOhm pull up resistor to 24 VDC if the PLC input is sinking. Most engineers skip this part because they assume the meter drives the input directly.
Q4. Is the Adafruit flow meter approved for food grade use?
No. The plastic materials may not meet FDA or 3A standards. For food and beverage, use a Silver Instruments sanitary electromagnetic flow meter or oval gear meter with tri clamp ends.
Q5. Can I use the Adafruit meter for diesel fuel?
Short answer is no. Diesel can swell the plastic and damage the turbine. Use a Silver Instruments oval gear flow meter for diesel. We have supplied these meters to fuel distribution customers in the Philippines.