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

Raspberry Pi Pico

Amazon
AliExpress

AD8495 K-Type Thermocouple Amplifier

Amazon
AliExpress

Jumper Wires

Amazon
AliExpress
SunFounder

Breadboard

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
(

)
# 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 *

/

)
+

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
(
"Temperature: {:.2f} °C / {:.2f} °F"
format
(
temperature_c
temperature_f
)
)
(
"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.
You can heat the thermocouple tip to observe the rise in temperature reading.
The maximum voltage Raspberry Pi Pico ADC can accept is 3.3V. Therefore the maximum temperature that can be sensed is +410°C.
This is how we can interface AD8495 K-Type Thermocouple Amplifier Raspberry Pi Pico using the MicroPython code to read the temperature reading.