Hi Rinus, You can use the AD849x series thermocouple amplifiers as "set point" comparator to control a relay via a simple relay driver transistor. If you take the output of the AD849x through a 2 input Exclusive-OR gate and pull the other input to the gate up or down then you can use an N channel MOSFET to drive the relay in either: 1. energised when the temperature is above Tset (XOR input A driven by AD849x OUT pin, XOR input B tied low) or; 2. energised when the temperature is below Tset (XOR input A driven by AD849x OUT pin, XOR input B tied high); [https://www.analog.com/en/products/ad8495.html#product-overview](https://www.analog.com/en/products/ad8495.html#product-overview)<br> <br> Please study the datasheet carefully, in particular the section on Setpoint Controller on page 15: [https://www\.analog\.com/media/en/technical\-documentation/data\-sheets/ad8494\_8495\_8496\_8497\.pdf\#\[\{"num":33\,"gen":0\}\,\{"name":"XYZ"\}\,52\,713\,0\]](https://www.analog.com/media/en/technical-documentation/data-sheets/ad8494_8495_8496_8497.pdf#%5B%7B%22num%22%3A33%2C%22gen%22%3A0%7D%2C%7B%22name%22%3A%22XYZ%22%7D%2C52%2C713%2C0%5D)<br> <br> and where it says "If the setpoint voltage is generated with a voltage divider, a buffer is recommended.", they mean use a circuit like in Fig 32 but driving the "sense" pin. The required setpoint voltage  for a given setpoint temperature is given by the same equation as that shown under Fig 33 on page 14: [https://www\.analog\.com/media/en/technical\-documentation/data\-sheets/ad8494\_8495\_8496\_8497\.pdf\#\[\{"num":30\,"gen":0\}\,\{"name":"XYZ"\}\,34\,693\,0\]](https://www.analog.com/media/en/technical-documentation/data-sheets/ad8494_8495_8496_8497.pdf#%5B%7B%22num%22%3A30%2C%22gen%22%3A0%7D%2C%7B%22name%22%3A%22XYZ%22%7D%2C34%2C693%2C0%5D)

Only problem is: nobody seems to have stock of the AD8495 K type version. :( Could you just use the AD8494 as an ambient temperature sensor? [https://www\.analog\.com/media/en/technical\-documentation/data\-sheets/ad8494\_8495\_8496\_8497\.pdf\#\[\{"num":30\,"gen":0\}\,\{"name":"XYZ"\}\,313\,693\,0\]](https://www.analog.com/media/en/technical-documentation/data-sheets/ad8494_8495_8496_8497.pdf#%5B%7B%22num%22%3A30%2C%22gen%22%3A0%7D%2C%7B%22name%22%3A%22XYZ%22%7D%2C313%2C693%2C0%5D) [https://uk.rs-online.com/web/p/instrumentation-amplifiers/8068013](https://uk.rs-online.com/web/p/instrumentation-amplifiers/8068013)<br> <br> Or some other dedicated temperature sensing IC?

You might get some other ideas from: [https://www.printfriendly.com/p/g/FcUBtd](https://www.printfriendly.com/p/g/FcUBtd) which is a copy of: [https://www.analog.com/media/en/technical-documentation/application-notes/an28f.pdf](https://www.analog.com/media/en/technical-documentation/application-notes/an28f.pdf) but with a note about the small mistake Jim Williams made about how a thermocouple really works. :)

Hello Andyfierman, thank you so much for all this information. I also want to say sorry because im not so good in electronics. I have already a thermocouple emplifier, but I dont understand howe to control a relay with this. To take the output through a 2 imput Exclusive -OR gate is to dificult for me. In real life am a plummer, you know. But if I have a simple circuit I can make it, and later with EasyEDA I can make a PCB with it, I can do that. But im not good enough to do all you say to me. Sorry because you realy try to help me. Rinus

Andfierman, this thermocouple amplifier i have, [https://nl.aliexpress.com/item/1005002555453801.html?spm=a2g0o.order_list.0.0.21ef79d2ImtHas&gatewayAdapt=glo2nld](https://nl.aliexpress.com/item/1005002555453801.html?spm=a2g0o.order_list.0.0.21ef79d2ImtHas&gatewayAdapt=glo2nld)

@sewertop, Ok. When you set a temperature, Tset, what do you want the relay to do: 1. energise when the temperature is above Tset or; 2. energise when the temperature is below Tset? Do you want any hysteresis around Tset (relay goes to one state at Tset then relay goes to the other state at Tset - Thyst)?

@sewertop, It is possible to design a relay driver circuit that could be built onto a second small PCB which takes the output from the module that you have and allows you to set a setpoint temperature Tset with a potentiometer and drives a 12V relay to control an AC load. You need to specify; 1. The supply voltage for the module (12V is assumed because that is the voltage you state for the relay); 2. The output voltage range of your module in terms of output voltage vs. temperature; 3. When you set a temperature, Tset, what you want the relay to do: 1. energise when the temperature is above Tset or; 2. energise when the temperature is below Tset? 4. Do you want any hysteresis around Tset (relay goes to one state at Tset then relay goes to the other state at Tset - Thyst)? 5. What type of load is the relay switching; 6. What load voltage is the relay switching; 7. What load current is the relay switching; 8. The operating temperature range of the module and the relay driver. * If you want new module designed with the AD597 and the relay driver on one board, please note that the AD597 is not recommended for new designs: [https://www.analog.com/en/products/ad597.html](https://www.analog.com/en/products/ad597.html) but LCSC show 87 in stock: [https://lcsc\.com/product\-detail/Temperature\-Sensors\_Analog\-Devices\-AD597ARZ\_C459145\.html](https://lcsc.com/product-detail/Temperature-Sensors_Analog-Devices-AD597ARZ_C459145.html)<br> <br> :)