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Thermal electronic sensing
Avoid paddles and mechanical parts that can jam or wear.
ifm · Flow switching
ifm SI Thermal Flow Sensors
Detect flow/no-flow and monitor medium temperature using compact insertion-style calorimetric sensors. SI is a strong route for pump protection, cooling-water confirmation and sanitary variants where a wear-free electronic flow switch is preferred.
ThermalFlow / no-flowLiquids & gasesIO-Link by modelSanitary variants
Published velocity3…100 cm/sFamily selection guide
Line sizes⅛"…8"With suitable fittings / installation
Medium temp.−25…80 °CFamily selection guide
Primary jobFlow / no-flowPump & cooling protection
Wear-free flow switching
Replace mechanical flow switches where simple, reliable flow confirmation is the goal
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Useful flow/no-flow sensitivity
SI is designed for flow-switch applications and can use low-flow accessories where appropriate.
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Additional process insight
Versions can monitor medium temperature in addition to flow.
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Digital status and process values
Current IO-Link-capable routes can expose flow velocity, temperature and switching status.
Applications
SI where cooling or circulation must be proven
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Run-dry prevention
Switch the control system when adequate flow is no longer present.
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Protect heat-sensitive equipment
Confirm that enough cooling water reaches the process and monitor temperature where supported.
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Food & beverage process fittings
Sanitary versions support suitable hygienic applications; verify exact approvals and fitting with the order number.
Calorimetric principle
Flow changes the heat removed from the sensor tip
The SI tip evaluates the temperature difference between a heated measuring element and a medium-reference element. As flow increases, more heat is carried away. The sensor converts that change into flow indication and switching behaviour.
Teach-based switchingMany SI applications are commissioned around the actual flow condition rather than precision volumetric metering.
Liquids or gasesThermal technology can respond to many flowable media; final suitability remains application-specific.
Temperature changesRapid medium-temperature shifts can affect thermal measurement and should be considered.
Build-upCoating on the sensing tip alters heat transfer and can affect the response.
IO-Link
Read more than the switching output
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Up to 140% of taught rate
IO-Link can provide current flow velocity relative to the taught operating point.
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Current medium temperature
Use the same device to expose temperature where the selected model supports it.
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Digital machine feedback
Read the current switching state together with process values.
Family selection
SI is a flow switch first—not a high-accuracy consumption meter
| Requirement | Recommended ifm route | Why |
|---|---|---|
| Simple flow/no-flow, liquids or gases | SI thermal flow switch | Primary fit Wear-free insertion sensing |
| Large-pipe flow + temperature trend | SA thermal | Broader insertion-length and absolute/relative flow options |
| Compressed-air consumption / leak energy | SD | Totaliser and gas-consumption focus |
| Accurate conductive liquid flow | SM magnetic-inductive | Inline volumetric measurement with higher accuracy |
| Fast water / oil process monitoring | SB | Mechatronic route with very fast response |
Family envelope from ifm's current selection guide: approximately 3–100 cm/s, ⅛"–8" line sizes, −25…80 °C medium temperature, with sanitary versions available. Exact limits are order-number specific.
Installation
Put the sensing tip fully into the moving medium
Thermal sensors are installation-sensitive
Make sure the probe tip is surrounded by the flowing medium and avoid locations where empty pipe, air pockets, deposits or turbulence make the heat-transfer condition unstable.
InsertionTip must be within the flowing medium
Pipe fillSelect a position that remains properly wetted / exposed to the gas stream
Medium changesRapid temperature changes can affect response
DepositsBuild-up changes thermal coupling
OutputSwitching, analogue and/or IO-Link depends on exact model
AccuracyUse a dedicated meter family if accurate volumetric consumption is required
Requirement capture
Inputs required to select the SI flow switch
MediumLiquid or gas, including concentration / viscosity where relevant.
Pipe sizeInternal diameter and process connection.
Flow conditionNormal flow and minimum acceptable flow / no-flow threshold.
TemperatureMedium temperature range and rate of change.
PressureNormal and maximum process pressure.
OutputSwitch point, analogue, temperature and IO-Link needs.