Fuel Stick Sensor (FS-3)

The FTS FS-3 electronic fuel stick sensor is commonly deployed on-site near prescribed burn and wildfire operations. The sensor’s output tracks closely with 10-hour fuel moisture, an invaluable indicator of fire behavior. The sensor uses digital compensation and linearization to provide a greater degree of precision and better temperature performance than analog sensors.

The FS-3 provides an electronic measurement of the internal temperature and humidity of a wooden dowel. Based upon a 10-hour fuel stick algorithm, these measurements are used to indicate the moisture content of naturally occurring fuels in the vicinity of the weather station.

The FS-3 dowel is manufactured from clear kiln-dried ponderosa pine with 10-14 annual growth rings per inch. The dowel is hollowed with a machine ream to ensure precise repeatability between sensors.

The dowel is simple to replace in the field—it simply screws onto the end of the FS-3 housing, with the thermistor and humidity sensor protruding into the dowel’s interior. The replaceable dowel keeps maintenance and replacement costs low.

Fuel temperature is monitored by a precision thermistor, and fuel moisture by a capacitive humidity sensor. Exposed to the elements, the FS-3 acts to integrate the varying effects of direct sunshine, wind, rain, air temperature and humidity over a period of time.

The FS-3 includes an armored stainless steel cable and bayonet connector, providing fast and simple mating to the “fuel stick” port on the Axiom datalogger.