I have designed a thermocouple meter for use for obtaining temperature readings from thermocouples. Its used together with the thermal chamber described elsewhere on this site.
The design is done primarily as a programmable instrument, but it has a OLED display, so it can show the current temperature. The programming uses SCPI, the same type of programming strings that most newer (1990 forward) instruments use.
The meter consists of a Empyrean microcontroller from Etherkit and a couple of MAX31855 thermocouple amplifiers. For the MAX31855 it is important to get them from a reputable source, not ebay or aliexpress as there is a lot of fakes around. Display, connectors for the thermocouples and such parts are from ebay.
This design requires a Etherkit Empyrean or other SAMD21 series microcontroller. It will not work with other arduino boards.
The enclosure used is a cheap e-bay case 100x75x35mm. For this I have selected to mill out new font and back panels.
There are 2 PCBs that interlock on this design, a main PCB that fits the enclosure and holds most of the parts and a display PCB for fixing the display in the correct position.
The greenwires are fixed in the last version of the board.
There is a planned extention header (8 pole connector) for a 2. board of thermocouple amplifiers. This way the meter can measure up to 4 points in the same meter.
A couple future points that should be inproved up on is the voltage regulator. This should be replaced with a small switch mode regulator to 5V and a linear regulator down to 3.3V. This have been used in several of my other design and I consider that a building block now. Correctly build it radiates no detectable noise.
Another point of improvement is that USB is finky at best. It would be better to replace this with a network connection. Experience is that USB times out after a while and that interrupts measurement over longer periods. Adding a network card should be easy and there is plenty of space in the microcontroller.
Feel free to try it, change the code and play around with it. A limited amount of PCB’s and panels may be available from me.
RF and electronics blog LA3PNA 