Please note: All our kits will be sold via The Curious Electric Company from now on. This page is for information only. Please visit our shop to see our current range of kits or contact us to discuss your project and how we might be able to help.
This is a K-type (or J-Type) thermocouple amplifier which can be used to amplify the tiny voltage from a thermocouple to a higher voltage, readable by a microcontroller. Thermocouples can be used to measure very high temperatures, but they only output a very low voltage, hence the need for this amplifier.
This kit is based upon the AD8495 precision K-type thermocouple amplifier, or the AD8494 J-type version. The board requires a 5V supply and gives a linear output of 5mV per degree C. The circuit board contains filtering for the standard amplifier configuration. It can be used to measure temperatures up to 1000C.
Please Note: This page is for reference only. Please see here for the most up to date information.
I had designed and built a temperature controller for a reflow soldering oven which used this thermocouple amplifier. A couple of people asked me about this circuit so I decided to quickly make a simple breakout PCB.
This converter can be used anywhere you need to measure high temperatures – such as soldering temperatures, flue and exhaust gas temperatures, BBQs and ovens.
Below 100C I would generally use a thermistor, but not many thermistors are rated for temperatures above 150C. In that case we need to use a thermocouple which output a tiny voltage. This must be amplified and filtered so that it can be read by the ADC in a micrcontroller.
Buy one here:
This is a relatively simple to put together kit, although it does have one surface mount IC to solder. The kit includes the following parts:
Note: You will need: soldering iron, solder, wire cutters.
The construction instructions are available here:
Here is the circuit schematic:
|Screw Terminals for thermocouple
|AD8495 SMD K-type thermocouple amplifier
KiCAD design files
The PCB and schematic for this project were drawn using the open-source KiCAD electronics design package.
Here is the PCB and layout design:
Testing the output
Here the board is set up with a multimeter and hot air gun to heat the thermocouple:
The output voltage is 1.373V, which equates to 1.373V / 5mV = 274C. This could be easily read by the ADC in a microcontroller.