Donut probe.

A contact thermocouple with a ring-shaped tip that is set into the printed ink layer and reads the temperature of the ink itself as the print heats. It measures at the junction of two fine crossed wires, and those wires have to be buried in the deposit; sitting on top of it, they read the air around the print instead. An infrared gun reads reflected heat off the surface and can show a number well above what the ink has actually reached, which is how a print that hit cure temperature on the gun still washes out. Verifying with the gun alone lets a shop run a full shift undercured and learn about it weeks later, through returns, on work that is already invoiced.