Testo 549i Refrigeration Pressure Probe

The Testo 549i is a refrigeration pressure probe in the Testo Smart Probes family. It threads directly onto a 7/16 in. UNF (1/4 in. SAE) Schrader service port with no hoses, reads the high or low side of an air conditioning, heat pump, or refrigeration system, and sends the reading over Bluetooth to measureQuick or the testo Smart App. The current second-generation probe adds a 45° angled connection and a Bluetooth range of up to 350 ft.

Refrigerant Pressure Measurement

The 549i reads from -14 to 870 psi at 0.1 psi resolution, twice per second. Accuracy is ±0.5% of full scale ±1 digit, which works out to about ±4.5 psi anywhere in the range. As with any gauge rated on full scale, that fixed band is a larger share of a low-side reading than a high-side one: ±4.5 psi is about 3.7% of a 120 psig suction pressure and about 1.1% of a 400 psig liquid pressure.

measureQuick Wireless Integration

The 549i connects to measureQuick over Bluetooth alongside the other Testo Smart Probes on the job. measureQuick converts the pressure to a saturation temperature for the refrigerant selected on the test, and with a 115i clamped on the same line it calculates superheat or subcooling. Two 549i probes, one on each service port, cover both sides of the system, and the readings go into the test record with no hand transcription.

Build and Field Readiness

The 549i measures 5.9 x 1.3 x 1.2 in. and runs about 130 hours on three AAA batteries. With no hoses to fill and purge, less refrigerant escapes at each connection. It operates from -4 to 122 °F (-20 to 50 °C), ships with batteries and a calibration certificate, and carries a 2-year Testo warranty.