ExpertTest and Measurement
Dual Thermocouple Temperature Monitor
Read two Type-K thermocouples using two MAX6675 converter breakouts and compare temperatures on a display or serial console.
Parts from the database
- MAX6675ISA+ × 2One converter per thermocouple; use on breakout boards
- Raspberry-Pi-Pico × 1Microcontroller host
Other supplies
- two MAX6675 breakout boardsCommon build supply
- two Type-K thermocouplesCommon build supply
- Pico boardCommon build supply
- jumper wiresCommon build supply
- USB cableCommon build supply
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Connections
- Share SPI SCK and SO/MISO from both boards; connect each CS to its own GPIO (GP17 and GP16).
- Power each MAX6675 board according to its breakout documentation; the IC itself is a 4.5–5.5 V part, so verify logic compatibility with a 3.3 V Pico.
- Observe thermocouple +/− markings and keep probe leads away from motor and heater wiring.
Build steps
- Run a one-sensor library example first, then duplicate it with a separate chip-select pin.
- Read both channels at a modest interval and label each probe in software.
- Compare the probes side-by-side in room air, then measure a warm object without exceeding probe or module limits.
- Log differences and do not assume matched probes are calibrated to each other.
Software and firmware setup
Firmware is required, but a complete two-channel sketch is not included yet. First run a MAX6675 library example with one breakout, then instantiate a second reader with a separate chip-select pin while sharing clock and data. Verify logic-level compatibility of each breakout before connecting it to a 3.3 V Pico.
Test your build
Both channels should report plausible temperatures and respond independently when only one probe is warmed.
Troubleshooting
- If one channel reads open-circuit, check thermocouple continuity and polarity.
- If both channels show the same data, verify independent CS pins.
- If the Pico cannot read 5 V logic, add a suitable level shifter or choose a verified compatible breakout.
Safety and limitations
The bare MAX6675 is not a 3.3 V supply part. Use a breakout with documented level compatibility. Keep probes away from mains and hot surfaces beyond their rating.
Manufacturer and platform documentation
Community Notes for This Project
These are unverified visitor contributions, separate from the build guide and manufacturer specifications. Verify technical advice against the linked datasheets before relying on it.
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