IR Thermometer
No contact, and it tells you whether you are aimed
Page 42 uses an MLX90614 (I2C 0x5A) for contactless temperature: object and ambient temperature as two large numbers, with the difference below — a gap above 5 °C is reported as “on target”, meaning something is actually in the field of view. The health score sits at the bottom.
★ Register reads must use a repeated start: write the command byte, then `endTransmission(false)` before reading. A stop-then-start sequence makes some modules return their previous cached value, which shows up as “the temperature never changes” — it looks like a hang but is a bus timing problem.
On-screen interface
A recreation of this page on the 2.41-inch AMOLED display (600 × 450). Actual interaction and layout follow the latest firmware.
Key capabilities
Contactless
Measure water, motor housings or skin without touching anything.
Aim check
A 5 °C gap between object and ambient means you are on target.
Repeated start
Proper SMBus sequencing, so no stale cached reads.
Health score
Reply, ID, plausibility and stability, scored separately.
Technical specs
Typical scenarios
Motor / chip check
Sweep a board after a load run to find the hot spot.
Water temperature
Measure without putting a probe in the water.
Related commands
page 42 Open the IR thermometer mlx Read object and ambient temperature once mlx on | off Start or stop periodic sampling
- Shiny metal has an emissivity of 0.1–0.3 and reads far too low — tape a patch of matte tape first.
- The field of view is about 90°, so small targets need a short distance.
- Repeated start is mandatory; a stop-then-start read keeps returning the cached value.