Company Profile

Sensirion Flow Sensors and Sensirion Flow Meters for Medical Gas Applications

Quick Answer: Sensirion flow sensors use microfluidic thermal chips to measure medical gas flow inside ventilators, anesthesia machines, and oxygen concentrators. The SFM3019 sensor covers -10 to 240 slm with response time below 10 ms. For medical gas plant headers and hospital distribution pipes, Silver Instruments thermal mass flow meters handle DN15 to DN100 with 4-20 mA HART output.

How Sensirion Microfluidic Thermal Chips Work

Sensirion builds its flow sensors on the CMOSens platform. A small thermal heater and two temperature sensors sit on a silicon microfluidic channel. Gas flows across the channel. The heater warms the gas flow. The temperature sensors measure the thermal shift. No moving parts and no laminar flow element sit in the gas path. This design keeps pressure drop very low. In a ventilator, the flow path may operate at 5 to 60 mbar. A high pressure drop would waste oxygen and reduce battery life in portable equipment.

The SFM3019 is a common sensor for medical gas mixing. Its measuring range runs from -10 to 240 slm. Accuracy is 2 percent of measured value. Response time is below 10 ms. That speed matters for breath-by-breath flow measurement in ICU ventilators. The SFM4100 covers smaller flows from 0 to 20 slm. It uses the same thermal measurement principle without moving parts.

Where Sensirion Flow Meters Fit Inside Medical Equipment

Common applications include ventilator inspiratory and expiratory flow detection, anesthesia fresh gas flow measurement, CPAP leak compensation, and oxygen concentrator total output. A typical ICU ventilator may use two Sensirion sensors. One sits on the inspiratory side before the humidifier. Another sits on the expiratory side where moisture and condensation are present. The sealed CMOSens chip handles that exposure.

Anesthesia machines often blend oxygen, air, and nitrous oxide. The gas mixer needs a fast flow feedback signal. Sensirion flow sensors provide that signal within milliseconds. This helps the machine hold a precise oxygen fraction during surgery.

Industrial Side of Medical Gas Flow Measurement

Here is the thing. Microfluidic thermal chips work well inside a device. They are not built for a DN40 or DN65 hospital oxygen header at 6 to 10 bar. For that job, you need an industrial thermal mass flow meter. Silver Instruments supplies thermal mass flow meters for medical gas production plants, hospital central gas headers, and oxygen filling systems. These meters measure mass flow directly. Pressure and temperature changes do not corrupt the reading as much as a volumetric meter.

Silver Instruments does not resell Sensirion sensors. We supply industrial thermal mass flow meters for medical gas production and hospital distribution lines. The Silver Instruments model TMF-1000 thermal mass flow meter covers DN15 to DN100 pipes. The flow range goes from 0.5 to 1000 kg/h for air equivalent. Accuracy is plus or minus 1.0 percent of reading plus 0.5 percent of full scale. Output options include 4-20 mA HART and RS485 Modbus. Process temperature range is -20 to 150 °C. Pressure rating is 16 bar. For smaller medical gas lines, the TMF-500 covers DN6 to DN25 and 0.1 to 50 kg/h.

Last year a medical gas plant in Vietnam asked us about a DN50 oxygen header meter. Operating pressure was 7 bar and flow was 0 to 250 kg/h. We recommended the TMF-1000 with PT100 compensation and 4-20 mA HART output. The plant used it for daily oxygen consumption tracking across three hospital buildings. Most engineers skip microfluidic chips for this pipe size because the installation would need complex adapters and pressure reduction.

Parameters That Matter for Medical Gas Flow Measurement

Gas type matters first. Oxygen, medical air, nitrous oxide, and carbon dioxide have different ther