With portable units for snap-shot measurements, immersion temperature probes are generally used, protruding 50 mm into the fluid flow. These require tapping points before and after the pump, in pipe work.

Immersion temperature probe passing into fluid via a T-piece and gate valve. A pressure probe is also attached to the T-piece.

A constraint is that the unsupported length of the temperature probe should be within certain limits, depending on the water velocity, to avoid vibration and excessive stress due to vortex shedding.