S401 Thermal Mass Flow Meter for Compressed Air and Gases (Insertion-Sensor)

Easy-to-use insertion flow meter to accurately measure the flow in compressed air systems.

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Efficient compressed air and gas system monitoring

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Independent of pressure and temperature changes

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Mobile App for remote configuration and live readings

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Measures standard flow and total consumption

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Fast response time over a wide measuring range

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Color displays to show values and for sensor settings

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Isolated 4... 20 mA & Pulse; Modbus/ RTU; Modbus/ TCP; M-Bus

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Installation under pressure (DN25 to DN500)

The SUTO S401 Insertion type, Compressed Air Flow Meter offers an easy to use and affordable compressed air and gas monitoring solution. Due to the wide measurement range and high reliability, the flow meter can be used in various applications.

Thermal Mass Flow Technology

The S401 is a thermal mass flow meter, based on its measurement principle it’s not required to compensate the compressed air pressure and temperature. So, there is no need of any additional temperature and pressure measurements to measure the standard flow and the consumption.

Measurement of Different Gases

The S401 is well suited to be used in any other gases such as Nitrogen, CO2 and many other technical gases with the use of the thermal mass principle. Gas types can be easily switched in the sensor settings with pre-defined gas calibrations for various gases to maintain accuracy. The S401 sensor technology offers a high resolution and a high sampling rate, which results in a fast and precise measurement. The flow meter can save two calibration curves, and so the sensor can be used in two different gases without any loss of accuracy.

Optional Color Display

The optional color display is designed to show all measured values such as actual flow and total consumption. The display can be used to manage the sensor settings like pipe diameters, gas types and output settings.

Various Signal Outputs

The S401 Flow Meter offers different signal output options. It can be equipped with an isolated analog and pulse output to read out the compressed air flow and the total compressed air consumption.

Alternatively, a Modbus/RTU or Modbus/TCP interface can be used to access all measured values via the digital interface. The S401 can also be equipped with a 2-wire M-Bus output for digital meter reading.

This allows the sensor to be easily connected to SUTO displays, like the SUTO S331 Data Logger and/or third party displays and PLCs. The S401 can also be connected directly to monitoring software solutions.

Easy Installation

With easy installation under pressure through a standard ball valve, it can be simply removed and re-installed for calibrations. This means the shutdown of the compressed air systems as well as the resulting downtime and costs can be avoided. Various settings such as gas type, flow unit and reference standards, can be set ex-factory according to your needs.

Online Readings and Configuration Through Smartphone App

The free S4C-FS mobile phone app helps the user to easily configure the sensor to their needs. The app gives you the option to change settings wirelessly on site. Managing compressed air has never been easier.

Should you have any special requests, for example custom flow ranges or different gas types, please contact us here.

Read more

  • Compressed air / gas consumption and flow measurement in main and distribution lines
  • Compressed air allocation costs within distribution network

Monitoring of efficiency and performance of compressed air and gas systems


Accuracy1.5 % of reading ± 0.3 % FS (optional 1 % of reading)
Selectable unitsm3/h, m3/min, l/min, l/s, cfm, kg/h, kg/min, kg/s
Repeatability0.25 % of reading
SensorThermal mass flow sensor
Sampling rate10 samples / sec
Turndown ratio200:1
Response time (t90)0.1 sec
Selectable unitsm3, ft3, l
Reference conditions
Selectable conditions20 °C 1000 mbar (ISO1217),
0 °C 1013 mbar (DIN1343)
freely adjustable


Analog output
Signal4 ... 20 mA (4-wire), isolated
Scaling0 ... max flow, freely adjustable
Loadmax. 250 Ohm
Update rateValue updated ever 1 sec
Pulse output
SignalSwitch output, normally open, max. 30 VDC, 20 mA
Scaling1 pulse per consumption unit (selectable)
ProtocolModbus/RTU, Modbus/TCP
Update rateValue updated ever 1 sec
Voltage supply15 ... 30 VDC
Current consumptionmax. 200 mA


WirelessS4C-FS App for mobile phones
PC SoftwareUSB Service Kit + Software
OthersDisplay with 2 touch buttons
Integrated2.4” color graphic display with 3 touch buttons
Process connectionStainless steel 1.4404 (SUS 316L)
HousingPC + ABS
SensorCeramic, glass coated
Metal partsStainless steel 1.4404 (SUS 316L)
Electrical connection2 x M12 (5 pole); 1 x M12 (8-pole x-coded) for TCP
Protection classIP65
ApprovalsCE, RoHS, FCC
Process connectionS401: G1/2” (ISO 228/1)
S421: Measuring section with R-thread or Flange
WeightS401: 0.9 kg
S421: 0.4 kg (without measuring section)
Operating conditions
MediumAir, N₂, O₂, CO₂ and other gases
Medium qualityISO 8573: 4.4.3 or better
Medium temperature-30 ... +140 °C
Medium humidity< 90 % rH, no condensation
Operating pressuremax. 5.0 MPa (> 1.6 MPa need installation device)
Ambient temperature-30 ... +70 °C, -10 ... +50 °C (with display)
Ambient humidity< 99 % rH
Storage temperature-30 ... +70 °C
Transport temperature-30 ... +70 °C
Pipe sizesS401: ½” ... 12” (bigger pipes on request) S421: ½” ... 3”

Volumetric Flow Ranges

Pipe SpecificationsS401S421
AnschlussgewindeDNDI (mm)S401-S (m3/h)S401-M (m3/h)S401-H (m3/h)Measuring range from to
½”DN15--0.5 ... 90 m3/h
¾”DN20--0.9 ... 170 m3/h
1”DN2527.30.5 ... 147.70.6 ... 294.70.6 ... 356.91.5 ... 290 m3/h
1¼”DN3236.00.9 ... 266.31.2 ... 531.51.2 ... 643.52 ... 500 m3/h
1½”DN4041.91.2 ... 366.71.5 ... 731.91.5 ... 886.23 ... 700 m3/h
2”DN5053.12.0 ... 600.12.5 ... 1197.63.0 ... 1450.04 ... 1000 m3/h
2½”DN6568.93.5 ... 1026.55.0 ... 2048.65.0 ... 2480.46 ... 1500 m3/h
3”DN8080.95.0 ... 1424.47.0 ... 2842.77.0 ... 3441.98 ... 2500 m3/h
4”DN100100.010 ... 2183.312 ... 4357.212.0 ... 5275.7
5”DN125125.013 ... 3419.618 ... 6824.418.0 ... 8263.1
6”DN150150.018 ... 4930.125 ... 9838.925.0 ... 11913.1
8”DN200200.026 ... 8785.633 ... 17533.342.0 ... 21229.5
10”DN250250.040 ... 13743.952 ... 27428.560.0 ... 33210.7
12”DN300300.060 ... 19814.880 ... 39544.1100.0 ... 47880.4


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S401 / S421

Info sheets
S401 / S421
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S401/ S402/ S415/ S418/ S418-V/ S421/ S430/ S450/ S452/ S460 /S461 /S462 – CE & UKCA DECLARATION OF CONFORMITY

S401/ S402/ S415/ S418/ S418-V/ S421/ S430/ S450/ S452/ S460 /S461 /S462 – CE & UKCA DECLARATION OF CONFORMITY
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S4C-FS App Android: V2.0.1

S4C-FS App Android: V2.0.1
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