Arduino UNO Pressure Measurement – Detailed Example

This example demonstrates how to measure gauge pressure using an Arduino UNO and a 0–5V pressure sensor. The voltage is converted into multiple pressure units:

The sensor’s voltage output is linearly proportional to gauge pressure.

Detailed Steps
Arduino Code ✅ 

/*
 * © 2024 Copyright Peter I. Dunne, all rights reserved
 * Prepared for educational use
 * Released under the Mozilla Public License
 * Arduino UNO Pressure Measurement
 * Measures gauge pressure and converts readings to Pascals, kilopascals, bar, PSI, and ATM.
 */

const int pressurePin = A0;
const float VRef = 5.0;
const int maxADCValue = 1023;

// ─── Sensor parameters (updated for ratiometric 0.5–4.5V sensors) ───
const float vmin = 0.5;     // Sensor output at 0% pressure
const float vmax = 4.5;     // Sensor output at 100% pressure
const float pmax = 10.0;    // Full-scale pressure in bar
const bool gauge = true;    // true = gauge sensor, false = absolute sensor

// Unit conversions
const float barToPa  = 1e5;
const float barToPSI = 14.5038;
const float barToATM = 0.986923;

// Convert voltage to pressure in bar
float voltageToPressure(float voltage) {

    // If below vmin, clamp to zero pressure
    if (voltage <= vmin) return 0.0;

    // If above vmax, clamp to max pressure
    if (voltage >= vmax) return pmax;

    // Linear scaling
    float scaled = (voltage - vmin) / (vmax - vmin);  // 0 → 1 range
    float pressure = scaled * pmax;

    // Gauge sensors measure relative pressure
    // Absolute sensors include atmospheric baseline internally
    if (!gauge) {
        return pressure;   // absolute pressure directly
    }

    // Gauge = pressure above atmospheric, output already correct
    return pressure;
}

void setup() {
    Serial.begin(115200);
    Serial.println("Arduino pressure measurement, by Peter Ivan Dunne, ©2024");
    Serial.println("Released under the Mozilla Public License");
    Serial.println("https://jazenga.com/educational");
    Serial.println("Demonstration for 0-5v proportional pressure sensors (0.5–4.5V typical)");
    Serial.println("Calibration required for correct pressure range.");
}

void loop() {
    int adcValue = analogRead(pressurePin);
    float voltage = (adcValue / float(maxADCValue)) * VRef;

    float pressureBar = voltageToPressure(voltage);
    float pressurePa  = pressureBar * barToPa;
    float pressureKPa = pressurePa / 1000.0;
    float pressurePSI = pressureBar * barToPSI;
    float pressureATM = pressureBar * barToATM;

    Serial.print("Voltage: ");
    Serial.print(voltage, 3);
    Serial.print(" V | Pressure: ");
    Serial.print(pressureBar, 3);
    Serial.print(" bar, ");
    Serial.print(pressureKPa, 2);
    Serial.print(" kPa, ");
    Serial.print(pressurePa, 2);
    Serial.print(" Pa, ");
    Serial.print(pressurePSI, 2);
    Serial.print(" PSI, ");
    Serial.print(pressureATM, 2);
    Serial.println(" ATM");

    delay(1000);
}
How It Works

Most modern ratiometric pressure sensors powered from 5 V output a scaled voltage in the 0.5 V to 4.5 V range instead of a full 0–5 V sweep. This represents the usable pressure range while leaving headroom to detect wiring faults such as short-to-ground or short-to-supply.