Rugged, waterproof, and versatile, the probe includeds includes NIST-Traceable certificate. With a IP66 rating, it stops dirt, dust, fumes, and water from entering the meter. A microprocessor updates the display 2.5 times per second. Shock-resistant ABS plastic construction provides the ruggedness for use in any lab or plant. Supplied rubber boot for probe connector allows the unit to remain waterproof even with thermocouple probe attached. Push the REL button to activate the relative measurement mode; this feature measures the difference between a set point, "relative zero", and a measured value.