Fiber Optic Thermometer – Raytek Marathon FR Series


  • Simultaneous analog and digital outputs with user-defined alarms
  • Fast response time of 10 mSec
  • One or two-color operation
  • Fiber optic cable field replaceable
  • Fiber optic assembly withstands ambient temperatures up to 200°C (392°F)
  • High temperature fiber optic assembly withstands ambient temperatures up to 315°C (600°F)
  • Small fiber optic cable bend radius, less than 38 mm (1.5 inch) impervious to water and oil, NEMA-4 rated
  • High optical resolutions (>60:1) for measurement of small targets
  • Small, compact optical head with available close focus optics
  • Bi-directional RS-485 communications (networkable)
  • Supports up to 32 Marathon Series sensors on a single multidrop network
  • Programmable relay output (temperature setpoint or “fail safe”)
  • DataTemp® MultiDrop software for remote configuration and monitoring
  • Field calibration and sensor diagnostics software included

The Marathon FR fiber optic thermometer accurately measures targets that are: obstructed by smoke, steam, particulates, or smaller than the instrument field of view or located within strong electromagnetic fields. This pyrometer consists of a rugged fiber optic cable plus optical head assembly connected to a housing. The housing contains a detector, processing electronics, internal user interface/LED display, and termination connections for field wiring. The FR Optical Head consists of a small stainless steel cylindrical housing capable of withstanding ambient temperatures up to 200°C (392°F) or 315ºC (600ºF). The Optical Head accommodates an air-purge accessory to prevent lens contamination. The fiber optic cable is protected by stainless steel metal armor.

It includes Raytek DataTemp Multidrop software to enable easy and consistent installation, configuration and data capture across the following applications:

  • steel and metals processing (foundry/forging operations & heat treating)
  • glass forming, tempering, annealing, and sealing
  • semiconductor processing


Environmental Rating IP65 (IEC529) / NEMA-4
Ambient Temperature
Optical head 0 to 315°C (32 to 600°F)
Fiber cable 0 to 200°C (32 to 392°F)
optional up to 315°C (600°F)
Electronics housing 0 to 50°C (32 to 122°F)
with cooling platform up to 150°C (302°F)
Storage Temperature
Electronics housing -20 to 70°C (-4 to 158°F)
Relative Humidity 10 to 95%, non-condensing
Electronics housing IEC 68-2-27
Electronics housing IEC 68-2-6
Optical head 100 g (3.5 oz)
Electronics housing 710 g (25 oz)
Fiber Cable Protection rated to 200°C (392°F), stainless steel armour, Viton coated, IP65 / NEMA-4, provision for conduit to protect fiber cable
Outputs 0/4-20 mA; RS485, 2-wire or 4-wire, networkable to 32 sensors. Relay, 48 V, 300 mA, response time < 2 ms
Power Supply 24 VDC ± 20%, 500 mA


Raytek Marathon FR Series Fiber Optic Thermometer-DpstarGroup