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Thermal Dispersion Flow Switches for Liquids


Item# FST-221-SPST

 This item is available for quick shipping
Volume discounts available
Volume Discount Schedule
Quantity Price each
1-4 C$310.00
5-9 C$294.50
10-24 C$288.30
25-49 C$275.90
50-99 C$269.70
100+ C$263.50

In stock

Lead Time ( If not in Stock): 6 weeks

Thermal Dispersion Flow Switches for Liquids FST-221-SPST FST-221-SPST
  • 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
  • Excellent for Pump and Valve Monitoring of Critical Flows

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Media Type
Velocity Range
Max Operating Pressure
Max Process Temperature
Process Connection Type
Process Connection Size
Wetted Materials
Switch Rating and Type
Supply Power
Wire Length

Product Specs

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')

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
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Flow Switch With Compact Relay Controller
0 In Stock
Flow Switch With Compact Relay Controller
0 In Stock
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