Omega FST-321-SPST, FST-322-SPST, FST-323-SPST, FST-324-SPST Specification

Thermal Dispersion Flow
swiTches For use wiTh Gases

FST-320 Series

U Measure Mass

Flow of Gases

U High Reliability,

No Moving Parts

U Effectively Monitor

Critical Gas Flows

U May Be Used in Small

Piping or Large Ducts

U Standard with

SPST Relay

76 mm

(3")

FST-323-SPST
shown actual size.

114 mm

(4.5")

B

OMEGA’s FST-320 Series
thermal dispersion flow switches,
especially designed for use with
gases, sense changes in the heat
transfer characteristics of the
gases. Flow velocities from 1 to
90 fps are effectively monitored.
The flow switch incorporates a
standard SPST Relay switch output
for control flexibility. OMEGA®
controllers can easily be interfaced
to perform a variety of control
functions. The FST-320 family of
sensors can be easily installed in
line sizes ranging from 3⁄4 to 12".

FST-321-SPST
cutaway view

FST-321-SPST
shown actual size.

SPECIFICATIONS

Range: 1 to 90 fps
Accuracy: ±5% of setpoint at constant

temperature and flow rate
Response Time (Approx.):
10 sec, after initial 30 sec warm up

Set Point Drift with Fluid
Temperature: 0.5% per °C
Voltage Input: 12 to 36 Vdc @ 70 mA
Contact Output:

Selectable, NO or NC states

Fluid Temp. Rating:
0 to 60°C (32 to 140°F)

Maximum Fluid Pressure:

PP: 150 psi @ 25°C (77°F) derated
@ 1.667 psi per °C above 25°C (77°F)
Contact Materials: Polypropylene (PP)
with PVDF

Cable Length: 3 m (10')
Maximum Cable Run: 305 m (1000')
Dimensions: 76.2 or 114.3 x 26.7 mm

(3.0 or 4.5 x 1.05"), ³⁄₄ NPT

To Order

Model No. Material Size Use with Pipe Size
FST-321-SPST PP/PVDF 3" x ³⁄₄ NPT ³⁄₄ to 1¹⁄₂"
FST-322-SPST PVDF 3" x ³⁄₄ NPT ³⁄₄ to 1¹⁄₂"
FST-323-SPST PP/PVDF 4.5" x ³⁄₄ NPT 2 to 12"
FST-324-SPST PVDF 4.5" x ³⁄₄ NPT 2 to 12"

Comes complete with operator’s manual.
Two extended cable lengths available: for 7.62 m (25') add suffix “-25” for additional cost

PP/PVDF, or PVDF; for 15.24 m (50') add suffix “-50” for additional cost, for PP/PVDF or
for PVDF.

Ordering Examples: FST-321-SPST, polypropylene flow switch.
FST-323-SPST, polypropylene flowswitch, 4.5 x

B-88

3

⁄

4

NPT.