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Thermal Dispersion Flow Switches for Liquids


Item# FST-211-SPST-25 FT

In stock

Lead Time (If not in stock): 8 weeks
Thermal Dispersion Flow Switches for Liquids FST-211-SPST-25 FT FST-211-SPST-25 FT
  • High Reliability — No Moving Parts
  • Very Low Flow Detection–Down to 0.04 FPS Liquids
  • Use in 1/8 through 12' Pipe or Tubing
  • SPST Relay Standard

FST-211-SPST-25 FT Model Options

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Wire Length
Connection Size
Flow Rate
Body Material
Switch Type
Compatible Media
Pipe Size

  • Maximum Pressure PP or PVDF: 150 psi @ 25°C (77°F) derated @ 1.667 psi per °C above 25°C (77°F)
  • Minimum Supply Voltage 12 VDC
  • Switch Operation selectable
OMEGA™ FST-200 Series flow switches use thermal dispersion technology to create a very accurate and economical method of sensing flow. Monitor fluids from 0.4 to 1.2 specific gravity, 1 to 300 cp, and pulsating flow from 10 to 100 pulses per minute. The sensors incorporate two temperature probes, one of which is heated. The flow of liquid reduces the temperature of the heated probe, decreasing the temperature differential with the non-heated probe. OMEGA’s LVCN-131 and LVCN-141 of controllers can easily be interfaced to perform a variety of control functions.

Range: 0.04 to 3 fps (liquids)
Accuracy: ±5% of setpoint at constant temperature and flowrate
Response time: 10 seconds after initial 30 sec warm up
Setpoint Drift with Fluid Temperature: 0.5% per °C
Voltage Input: 12-36 Vdc@70 mA
Contact Output Mode: selectable, NO or NC states
Fluid Temperature: 0 to 60°C (32 to 140°F)
Max Fluid Pressure (PP or PVDF): 150 psi @ 25°C (77°F)
derated @1.667 psi per °C above 25°C (77°F)
Wetted Materials: PP and PVDF
Cable Specifications: 3 m (10 ft)
Max Cable Length: 305 m (1000 ft)
Dimensions: 76.2 or 114.3 x 26.7 mm dia. (3.0 or 4.5 x 1.05')
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Rated 1 out of 5 by from Great product! Unacceptable service I have one installed in a housing I made myself, and it has been working perfectly for about a year now.
Date published: 2017-05-12
Rated 3 out of 5 by from Flow Switch service replacements Sensors worked good, Many challenges to overcome for DC power supply, DC relay connections, and additions of DC to AC relays for proper operation
Date published: 2020-08-03
Rated 1 out of 5 by from Documentation sucks I guess these sensors connect themselves because there is ZERO info on the color code and wiring for NPN or PNP. No flow data either?????
Date published: 2019-09-26
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How does one set the flow at which the device switches?

Asked by: DavidD
Thank you for your inquiry. There's a potentiometer on the flow switch which you can use to set the switch point. Full instructions to set a switch point can be found in the manual on page 12.
Answered by: AS Engineer
Date published: 2019-08-18

Can this unit be used in a wash down area; is the housing sealed against water ingress?

Asked by: BCB13
Thank you for your inquiry! These sensors have a NEMA 4X rating and should not have any issues in a washdown area.
Answered by: Application Engineer JM
Date published: 2021-11-12
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Flow Switch With Compact Relay Controller
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Flow Switch With Compact Relay Controller
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