How to Use Adafruit AD8495: Examples, Pinouts, and Specs

The Adafruit AD8495 is a precision analog output K-type thermocouple amplifier which makes it simple to measure temperatures with a wide range using a type K thermocouple. It is designed to amplify the tiny voltage differences across the thermocouple's leads and convert them into a more easily readable output that correlates with temperature. The module includes cold-junction compensation and an analog output that can be interfaced with analog-to-digital converters (ADCs) on microcontrollers such as the Arduino UNO. This makes the AD8495 an ideal choice for a variety of temperature sensing applications in electronics, industrial systems, and hobbyist projects.

• Supply Voltage (Vcc): 3.3V to 5.5V
• Output Type: Analog voltage
• Temperature Measurement Range: -250°C to +750°C (with appropriate thermocouple)
• Output Voltage Range: 0V to Vcc
• Accuracy: ±2°C
• Cold Junction Compensation: Included
• Interface: Analog

1. Connecting the Module:

   • Connect the V+ pin to the 5V output on the Arduino UNO.
   • Connect the GND pin to one of the GND pins on the Arduino UNO.
   • Connect the VOUT pin to an analog input on the Arduino UNO (e.g., A0).
   • Connect the thermocouple leads to the TC+ and TC- terminals, ensuring correct polarity.

2. Programming the Arduino:

   • Use the analogRead() function to read the voltage from the AD8495 output.
   • Convert the analog reading to a temperature value using the appropriate conversion factor.

const int thermocouplePin = A0; // AD8495 output connected to A0

void setup() {
  Serial.begin(9600);
}

void loop() {
  int analogValue = analogRead(thermocouplePin);
  float millivolts = (analogValue / 1023.0) * 5000; // Convert to millivolts
  float temperatureC = millivolts / 5; // 5mV per degree Celsius

  Serial.print("Temperature: ");
  Serial.print(temperatureC);
  Serial.println(" C");

  delay(1000); // Wait for 1 second before reading again
}

• Ensure that the thermocouple wires are connected with the correct polarity to the module.
• Avoid placing the AD8495 near heat sources or areas with rapid temperature changes to prevent false readings.
• Use twisted pair wires for the thermocouple to minimize electrical noise and interference.
• When using long thermocouple wires, consider shielding and proper grounding to reduce potential signal degradation.

• Inaccurate Temperature Readings:

  • Check the thermocouple connections for correct polarity.
  • Verify that the AD8495 is not subjected to significant temperature gradients that could affect the cold-junction compensation.
  • Ensure that the Arduino ADC reference voltage is stable and accurate.

• No Output Voltage:

  • Confirm that the supply voltage is within the specified range and properly connected.
  • Inspect the thermocouple for any damage or disconnections.

Q: Can the AD8495 be used with other types of thermocouples? A: The AD8495 is specifically calibrated for type K thermocouples. Using other types may result in inaccurate readings.

Q: What is the resolution of the temperature measurement? A: The resolution depends on the ADC resolution of the microcontroller. For an Arduino UNO with a 10-bit ADC and a 5V reference, the resolution is approximately 0.488°C.

Q: How can I improve the accuracy of my temperature measurements? A: Use a stable power supply, ensure proper thermocouple connections, and calibrate the system if necessary. Additionally, using a microcontroller with a higher resolution ADC can improve the measurement accuracy.

For further assistance or inquiries, consult the Adafruit AD8495 datasheet and the support forums for community-driven troubleshooting and tips.