Siargo Mass Flow Sensors

FS4100 mass flow sensor

The FS4100 are general-purpose mass flow sensors with various ranges from 2 SLPM up to 50 SLPM, with analog and digital outputs.

The FS4100 mass flow sensors are an upgraded version of the 3rd generation FS4000 sensors that were first released in 2008. The series covers a wide dynamic flow range with a working pressure rating of up to 5 bar (73 psi), and a compensated temperature range from -10°C to 55°C.

The sensors are designed with an easy change of mechanical connectors. The standard connectors are BSPT 1/4" or one-touch connectors, and other customized ones are available upon request.

The sensing elements are manufactured with Siargo’s proprietary MEMS thermal mass flow sensing technology (Thermal‐D®) that measures the calorimetry and diffusivity of the flow medium. The sensor surface is passivated with silicon nitride ceramic materials and water/oilproof nano‐coating for performance and reliability. Compared to the conventional calorimetric flow sensing technology, this unique sensing approach offers better linearity, removes gas sensitivity for gases with similar thermal diffusivities, and improves temperature performance. It can also auto‐recognize pre‐programmed gases with significant differences in thermal diffusivity. It is the first in the industry that senses the mass flow with multiple gases without a manual gas conversion factor. As such, it ensures high precision for gas measurements with air calibration.

Thermal-D ® is a trademark of Siargo’s thermal sensing technology.


  • 2 choices of FS4103 for 2,3,4 or 5 SLPM versions or FS4108 for 10,20,30,40, or 50 SLPM versions
  • Pressure rating up to 5 bar
  • Output choices of RS485, I2C, 0.5 to 4.5V. Users may choose 1 output or a combined version or either RS485 & voltage or I2C and voltage.
  • Accuracy of ±1.5% + 0.2 FS
  • Various gas choices are available


  • Medical equipment such as anesthesia machines, endoscopes, and cancer treatment
  • Industrial applications such as welding machines, laser equipment, gas mixing and more