In situ heated oxygen probe with intrinsically safe output

An in situ oxygen analyzer (10) having an intrinsically-safe output (68) and a heated probe (12) is provided. The probe is extendable into a source of process gas and has an oxygen sensor (34) and heater (38) disposed therein. The heater (38) is configured to heat the oxygen sensor (34) to a temperature sufficient to operate the oxygen sensor (34). A housing is coupled to the probe and has first (36) and second chambers (64). The first chamber (36) is explosion-rated and includes non-intrinsically safe circuitry (50) coupled to the heater (38) to energize the heater (38). The second chamber (64) contains only intrinsically-safe circuitry (72) that complies with an intrinsically-safe specification. The first and second chambers (36, 64) are isolated from one another. The non-intrinsically-safe circuitry (50) is coupled to the intrinsically-safe circuitry (60) through an energy-limiting isolator (70).