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. Meter features Min/Max readings, Hold function, backlit display for reading in dimly lit areas, low-battery indicator, and auto shutoff.