AD8495 K-Type Thermocouple Amplifier Raspberry Pi Pico

Overview

In this tutorial we will be interfacing AD8495 Analog Output K-Type Thermocouple Amplifier with Raspberry Pi Pico using MicroPython Code. Earlier we used MAX6675 Thermocouple Amplifier with Arduino which is an SPI module. Similarly, we interfaced AD8495 with Arduino as well. The AD8495 is an analog output thermocouple amplifier.

The AD8495 thermocouple amplifiers provide a simple, low cost solution for measuring thermocouple temperatures. This hookup guide will help you to connect AD8495 K-Type Thermocouple Amplifier with Raspberry Pi Pico. The using the datasheet and the mathematical equation for temperature measurement, we will develop a MicroPython Code to read the temperature values.

Bill of Materials

Here are the list of components required for this tutorial.

S.N.	Components	Quantity	Purchase Link
1	Raspberry Pi Pico	1	Amazon \| AliExpress
2	AD8495 K-Type Thermocouple Amplifier	1	Amazon \| AliExpress
3	Jumper Wires	10	Amazon \| AliExpress \| SunFounder
4	Breadboard	1	Amazon \| AliExpress \| SunFounder

AD8495 K-Type Thermocouple Amplifier

The AD8495 K-Type Thermocouple Amplifier, developed by Analog Devices, is particularly suited for applications requiring high precision. As part of the AD8494/AD8495/AD8496/AD8497 family, it integrates precision instrumentation amplifiers with a cold junction compensator to directly produce a 5 mV/°C output from a K-type thermocouple signal.

This device simplifies the process of temperature measurement by combining an ice point reference with a precalibrated amplifier. This facilitates its use either as a standalone thermometer or as part of a switched output setpoint controller. Specifically calibrated for K-type (chromel-alumel) thermocouples through laser wafer trimming, the AD8495 ensures high accuracy across its optimized ambient temperature range. It supports a wide variety of supply voltages, from 3 V for direct interfacing with low-supply ADCs to up to 36 V for industrial systems requiring broad common-mode input ranges.

The temperature readings can be easily obtained by measuring the output voltage and applying the equation:

Temperature = (Vout – 1.25) / 0.005 V

For instance, a voltage reading of 1.5VDC translates to a temperature of 50°C. The device’s design minimizes self-heating with a total supply current of 180 μA when unloaded, although it is capable of delivering over ±5 mA to a load. This amplifier comes with a fully assembled PCB, which includes the AD8495 and a TLVH431 1.25V precision voltage reference, a 2-pin terminal block for easy connection to a thermocouple, and a pin header for breadboard integration. Refer to the AD8495 Datasheet for more information.

AD8495 Features & Specifications

Works with any K-type thermocouple
Will not work with any other kind of thermocouple other than K type.
Easy to use analog output.
Temp range with 5V power: -250°C to +750°C output(0 to 5VDC)
Temp range with 3.3V power: -250°C to +410°C output(0 to 3.3VDC)
Sensing Accuracy Range: ± 1°C around room temperature, ± 2°C for −25°C to +400°C
Sensing Temperature Max: 400°C
Sensing Temperature Min: -25°C
Supply Voltage: 3-18V DC

AD8495 Breakout Board Pinout

Power & Output Pins

V+ – This is the power pin. This board works with 3.3V and 5V power.
GND – Common ground pins
OUT – This is the output voltage pin. Read using an analog input.

Thermocouple Terminal

Red- – Connect the red or – wire on your thermocouple to this side of the screw terminal.
Ylw+ – Connect the yellow or + wire on your thermocouple to this side of the screw terminal.

Interfacing AD8495 K-Type Thermocouple Amplifier Raspberry Pi Pico

Now let us interface the AD8495 Analog K-Type Thermocouple Amplifier with Raspberry Pi Pico. The connection is very straight forward.

Connect the VCC of the AD8495 to the 3.3V Pi Pico.
Connect the GND of the AD8495 to a GND pin on the Pi Pico.
Finally, connect the Vout (output) of the AD8495 to GP26 of Pi Pico.

You may use a breadboard to place the AD8495 Module. Then, install the thermocouple on the thermocouple terminal of AD8495.

MicroPython Code

Now, lets write MicroPython Code Raspberry Pi Pico to read the AD8495 K-Type Thermocouple Amplifier Temperature values.

The following code runs on a Raspberry Pi Pico and uses an AD8495 analog thermocouple amplifier to measure temperature. It creates an Analog-to-Digital Converter (ADC) object for reading voltage from the AD8495, converts this voltage to temperature in Celsius, and then to Fahrenheit.

It continuously prints the measured temperature in both Celsius and Fahrenheit, along with the voltage reading, pausing for 0.5 seconds between each reading.

import machine

import time

# Create an ADC object on pin 26 (ADC0), which corresponds to physical pin 32 on the Pico

ad8495 = machine.ADC(26)

# Constants for calculations

VREF = 3.3 # Reference voltage for the Pico ADC

ADC_RESOLUTION = 65535 # 16-bit ADC resolution

def get_voltage(adc_pin):

"""Convert the ADC reading to voltage."""

return (adc_pin.read_u16() * VREF) / ADC_RESOLUTION

def celsius_to_fahrenheit(celsius):

"""Convert Celsius to Fahrenheit."""

return (celsius * 9 / 5) + 32

while True:

# Calculate the temperature from the AD8495 in Celsius

temperature_c = (get_voltage(ad8495) - 1.25) / 0.005

# Convert the temperature to Fahrenheit

temperature_f = celsius_to_fahrenheit(temperature_c)

# Print the temperatures and voltage

print("Temperature: {:.2f} °C / {:.2f} °F".format(temperature_c, temperature_f))

print("Voltage: {:.2f} V".format(get_voltage(ad8495)))

# Wait for 0.5 seconds before the next reading

time.sleep(0.5)

Copy the above code and paste it on the editor window of Thonny IDE. Save the file to raspberry Pi Pico Board with any name. Then run the code.

The code will print the analog voltage and then covert the voltage into temperature in both Celsius & Fahrenheit. The following image shows the value of room temperature.