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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.

This kit is available here for £10 (including UK P&P)

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.

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Buy one here:

This kit is available here. The cost is £10 (including p&p within the UK), or slightly more for Europe and worldwide.

Kit Information

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:

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Note: You will need: soldering iron, solder, wire cutters.

Instructions

The construction instructions are available here:

Circuit Schematics

Here is the circuit schematic:

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Parts List

The kit includes the following parts:
Reference Description
C1 1nf capacitor
C2 10nf capacitor
C3 1nf capacitor
C4 100nf capacitor
C5 100uf capacitor
C6 1uf capacitor
K1 Data connection
P1 Screw Terminals for thermocouple
R1 1M resistor
R2 10k resistor
R3 10k resistor
R4 100k resistor
U1 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:

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Testing the output

Here the board is set up with a multimeter and hot air gun to heat the thermocouple:

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The output voltage is 1.373V, which equates to 1.373V / 5mV = 274C. This could be easily read by the ADC in a microcontroller.