🛠 Lire un capteur analogique 0–10 V sur les entrées Opta

Objectives

Configure the multifunction inputs I1..I8 in analog mode to read 0–10 VDC transmitters. The Opta offers a user-configurable resolution from 12 to 16 bits (LSB 166 µV, accuracy ±5 %, repeatability ±2 %, acquisition cycle 10 µs). You will learn how to convert the raw reading into actual voltage using the onboard voltage divider (factor 0.3034).

Hardware

• Arduino Opta powered by 24 VDC
• One 0–10 V transmitter (pressure, temperature, powered potentiometer)
• Connections to I1, I2, I3 (pins A0, A1, A2) and common 0 V
• Arduino IDE, Opta core

Complete code

// opta_analogique_0_10v.ino — surveillance de 3 transmetteurs 0..10 V
const float VOLTAGE_MAX = 3.3;     // pleine echelle ADC
const float RESOLUTION  = 4095.0;  // 12 bits
const float DIVIDER     = 0.3034;  // diviseur embarque 10 V -> ~3,3 V
const int TERMINAUX[]   = {A0, A1, A2}; // borne I1, I2, I3

void setup {
  Serial.begin(9600);
  analogReadResolution(12); // 12..16 bits configurables sur Opta
}

void loop {
  for (int i = 0; i < 3; i++) {
    int brut = analogRead(TERMINAUX[i]);
    float volts = brut * (VOLTAGE_MAX / RESOLUTION) / DIVIDER; // 0..10 V
    Serial.printf("I%d : %d -> %.3f VDC\n", i + 1, brut, volts);
  }
  delay(1000);
}

Expected verification

With a transmitter outputting 5 V, the corresponding line displays approximately 5.000 VDC. By switching to analogReadResolution(16), decimal stability improves (oversampling). The measurable range is 0–10 VDC only in analog mode — not 24 V.

Common errors

• Sending more than 10 V to an input in analog mode: the range is 0–10 VDC; a 0–20 mA or 0–10 V signal must be respected, and a shunt resistor is required for current loops.
• Incorrect conversion factor: forgetting to divide by 0.3034 results in voltages that are off by a factor of 3; refer to the official sketch in the user manual.
• Misunderstood resolution: 16 bits in user configuration does not mean 16 bits of accuracy — accuracy remains ±5 %.
• Missing common ground: without a common 0 V between the sensor and the Opta, the reading drifts or oscillates.