HiLetgo DC 3-5V MAX6675 Module + K Type Thermocouple Temperature Sensor Thermocouple Sensor Set M6 Screw for Arduino

The MAX6675 works as advertised and is easily connected to an Arduino Uno R3 using the instructions supplied. The supplied thermocouple has a small enough thermal diffusivity that one must wait a bit in order to get a stable reading. I have used the supplied thermocouple to compare readings with an older K-type thermocouple using two of these boards. The readings were essentially identical. So while I do not have a way of checking absolute accuracy, I do see good repeatability. At room temperature the reading from the board is within 1 degree of an independent thermometer. The supplied thermocouple is not intended for high temperature operation, but does seem to operate up to at least 600 F. When doing so, the insulation in the lead cable smokes, but the reading is still good. I have been using this board with and Arduino and a different (high temperature capable and faster responding) K-type thermocouple to control a kiln up to 1500 F with good performance.

Decent accuracy: Ice water measures 40F, Boiling water measures 190F, higher temps correlate well with multimeter thermocouple. I'd say +/- 10F. Slow response time: The K junction sensor is a rugged solid and takes minutes to reach equilibrium temp. The Time Constant seems to be between 300 to 400 secs, depending on the temperature. Excellent price. Biggest complaint is that product should include a couple of M6 nuts. I had to make a trip to Home Depot.

The thermocouple controller (amplifier, error correction, ADC... MAX6675) works as intended. The thermocouple also seems to measure correctly but the response is very slow. After dipping the measure/hot end into boiling water, it took 30 seconds or longer to reach within a few degrees C of 100. I'm not sure if the measure junction is insulated well from the casing, if there's just a lot of thermal mass there, or if it's something else that causes the slow response time. Some other K-type thermocouples I ordered seem to be about just as accurate and respond to changes in less than a second. However, the junction at the measure end is exposed.

I ordered two of these. The boards both work as advertised. I checked the boards with a different thermocouple on the tip of my soldering iron. The tip measured around 280C, and I cross-referenced this with a different instrument which also read around 280C. The included thermocouple failed my soldering iron tip test. After over a minute the temperature only got to 180C. I then realized that I was comparing with tiny "bead"-style sensorss and this was not fair. I fired up my hot air gun, and placed the whole body of the sensor in the airflow. This time the temperature reading was as expected, and while it was still a slightly slower response than the bead thermocouple, this is to be expected and it's a perfectly serviceable sensor. I would say with this sensor, just beware that you need to completely soak it in the environment you are sensing. Just placing the tip on a surface you want to measure will give bad results.

The one I got was about on at room temperature, but read up to 90° C low at higher temperatures. I was testing with a hot air rework station and a known good thermocouple. The response time was very slow and laggy as well due to the bigger mass of the sensor housing probably. It was only changing about one degree centigrade per second, so yeah it took like two minutes to get up to 200°C. It’s basically useless for all my usage scenarios. Note that I am mostly reviewing the cheap quality thermocouple, not the amplifier board. It may be half decent if you have a good probe, but I was very disappointed not to get a working or useful product.

The probe interfaces with an ESP32 easily and covers a wide temperature range (including very high temperatures). It is well built and a small form factor with a metal lead. The module appears to provide accurate conversion from the probe to the ESP32. I have the probe installed into the flue of my woodstove to monitor the temperature and send the data to Home Assistant for monitoring. Saves me needing to check on the stove constantly.

4/20/21 Update: I received another device to replace this one and it worked great with no issues. One comparison of both boards I found a small solder ball that was shorting two leads of the IC. I removed the solder ball and this device now works also. With this I changed my review from one star to 5 stars as I should have noticed this problem. I am very happy with this device working well with a D1 mini and Tasmota. Old review: This board did not work. I have another board (different manufacture) working that confirms set up and program. Getting a replacement and will modify review if good.

Defective thermocouple. It gave wide swing of temperature reading and the reading is constantly changing. Since I am new to Arduino, it took me quite a while to figure out it's the thermocouple at fault. The seller has been helpful and very cooperative, and promised to send me a replacement thermocouple. I raised the rating for now for his good attitude, and may revise again when I receive the new part.