Product Description
2 Product Description
The Marathon FA/FR fiber optic series of instruments are high‐performance infrared thermometers. Each has a front end consisting of a small, fixed focus optical head coupled to a rugged fiber optic cable wrapped with a flexible stainless steel sheath. The fiber optic cable attaches to an electronics enclosure, which can be mounted away from the hot, hostile environment. The electronics enclosure can be connected to a computer with its two‐way RS485 interface.
Temperature measurements can be taken using either of the following modes:
•1‐color mode (FA and FR sensors) – for standard temperature measurements. The 1‐color mode is best for measuring the temperature of targets in areas where no sighting obstructions, either solid or gaseous, exist. The 1‐color mode is also best where the target completely fills the measurement spot and where the background or foreground are higher in temperature than the target.
•2‐color mode (FR sensors only) – temperatures are determined from the ratio of two separate and overlapping infrared bands. The 2‐color mode is best for measuring the temperature of targets that are partially obscured (either intermittently or permanently) by other objects, openings, screens, or viewing windows that reduce energy, and by dirt, smoke, or steam in the atmosphere. The 2‐color mode can also be used on targets that do not completely fill the measurement spot, provided the background is much cooler than the target.
Each model operates as a temperature measurement subsystem consisting of optical elements, spectral filters, detector, and digital electronics. All components are water‐tight NEMA‐4 (IEC 529, IP 65) rated and are built to operate on a 100 percent duty cycle in industrial environments. Simultaneous analog and digital outputs consist of standardized current signals commonly available for use with computers, controllers, recorders, alarms, or A/D interfaces.
Model | Description |
FA1A, FA1B, FA1C | |
| different temperature ranges |
FA1G | |
FA2A, FA2B | |
| different temperature ranges |
FR1A, FR1B, FR1C | |
| different temperature ranges |
| Table 1: Models |
2.1 Theory of Operation for 2‐Color Sensors
Two‐color ratio technology makes possible accurate and repeatable temperature measurements that are free from dependence on absolute radiated energy values. In use, a 2‐color sensor determines temperature from the ratio of the radiated energies in two separate wavelength bands (colors). The benefits of 2‐color sensors are that accurate measurements can be made under the following conditions:
•When the field of view to the target is partially blocked or obscured.
•When the target is smaller than the sensor’s field of view.
•When target emissivities are low or changing by the same factor in both wavelength bands.
2 | Marathon Series FA/FR |
