Wall Mount Ultrasonic FlowMeter
For Clean Liquids
U Accuracy 1%
U Repeatability 0.2%
U Positive, Negative and
Net Totalizer
U 4-Line LCD Display
U Clamp On Transducers
U RS232 Output
FDT-21W ultrasonic flowmeter is
designed to measure the fluid
velocity of liquid in a full/closed
pipe. It is a measurement system
which is both easy to install and
use. The FDT-21W operates
according to the difference in the
transit time of flight measured, and
determines the flow velocity by
measuring the travel time of a pulse
from one transducer to the next.
Flow in the same direction takes
less time to travel to the second
transducer than does flow in the
opposite direction. Electroacoustic
transducers receive and emit brief
ultrasonic pulses through the liquid
of the pipe. Transducers are
vertically placed at both sides of the
measured pipe. Sensors are placed
on the pipe and fastened by means
of a clamp. The display will quickly
show the flow velocity. The FDT-21W
can be used for metallic, plastic and
rubber tubes.
FDT-21W inside view.
FDT-21W shown smaller than actual size.
Accuracy: ±1% of reading >(0.2 m/s)
0.6 ft/s
Repeatability: 0.2%
Linearity: 0.5%
Response Time: 0 to 999 seconds
(user configured)
Velocity: (±0.01 to 30 m/s) ±0.03 to
105 ft/s bi-directional
Temperature Range:
Standard: 0 to 70ºC (32 to 158ºF)
With High Temp Transducers:
0 to 160ºC (32 to 320ºF)
Pipe Size: DN 20 to 100 mm (0.75 to
4") standard [up to DN 6000 mm (236")
with optional transducers]
Transducer Frequency: 1 MHz
Rate Units (User Configured):
Meter, feet, cubic meter, cubic feet,
USA gallon, oil barrel, USA liquid barrel,
imperial liquid barrel, million
USA gallons
Totalizer: 7-digit totals for positive,
negative and net flow
Liquid Types: Most liquids including
clean water, sea water, waste water,
chemical liquids, oil, crude oil, alcohol,
beer, and more
Suspension Concentration:
≤20,000 ppm (may contain very small
amounts of air bubbles)
Pipe Material: All metals, most plastics
and fiberglass
Security: Programmable lock-out code
Display: 4 x 16 english letters
Power: 85 to 264 Vac
Communications: RS232C (baud rate
from 75 to 115,200 bps)
Transducer Cable Length: 5 m (15')
Data Logger: Built-in, stores over
2000 lines of data
7-digit press-to-go for calibration
Housing: ABS plastic with aluminum
alloy protective carrying case
Case: NEMA 4 (IP65)
Dimensions: 100 H x 66 W x 20 mm D
(3.9 x 2.6 x 0.8")
Weight: 514 g (1.2 lb)
Accessories included
All models shown
smaller than actual size.
tranducer clamps
shrink tubing
FDT-21-S1 and
FDT-21-S1H tranducers
terminal lugs
FDT-21-GREASE-S1 and
acoustic gel
Alan wrench
Parameters HS-TypeHM-TypeS1-TypeM1-Type L1-TypeS1H-Type
20 to 100DN 50 to 100DN 20 to 100DN 50 to 700DN 300 to 6000DN 20 to 100DN 50 to 700DN
Pipe Size (mm)
Pipe Size (inch)
³⁄₄ to 4
2 to 28
³⁄₄ to 4
2 to 28
12 to 240
³⁄₄ to 4
2 to 28
Aluminum alloy
high-temperature materials
1 MHz
Calibrate with the main unit
0 to 70°C (32 to 158°F)
0 to 160°C (32 to 320°F)
NEMA 4 (IP65)
Protection Class
60 x 45 x 45
80 x 70 x 55
90 x 85 x 24
90 x 82 x 29
Dimensions (mm) 200 x 25 x 25 280 x 40 x 40 45 x 30 x 30
Weight g (oz)
250 (8.8)
1080 (38)
75 (2.6)
250 (8.8)
650 (23)
94 (3.3)
150 (5.3)
Fresh water, salt water, chemical liquids, oil, crude oil, alcohol, beer, etc.
Liquid Types
≤20,000 ppm, may contain very small amount of air bubbles
Pipe Material
All metals, most plastics, fiberglass, etc.
Standard length 5 meter x 2, can be extended to 10 meter x 2 or 15 meter x 2
Transducer Cable
To Order Visit omega.com/fdt21w for Pricing and Details
Model No.
Wall mount transit-time ultrasonic flowmeter (includes S1 and S1H transducers)
Comes complete with small pipe standard and high temperature transducers (S1 and S1H), acoustic gel, tape measure, RS232 cable,
transducer cable, tranducer clamps, alan wrench, terminal lugs, shrink tubing and operator’s manual.
Model No.
Description Weight g (oz) Pipe Size mm (inch)
Replacement small pipe standard transducer 75 (2.6)
20 to 100 (0.75 to 4)
Replacement small pipe high temperature transducer
94 (3.3)
20 to 100 (0.75 to 4)
Small pipe aluminum transducer
250 (8.8)
20 to 100 (0.75 to 4)
Medium pipe aluminum transducer
1080 (38)
50 to 700 (2 to 28)
Medium pipe standard transducer
250 (8.8)
50 to 700 (2 to 28)
Medium pipe high temperature transducer
150 (5.3)
50 to 700 (2 to 28)
Large pipe standard transducer
650 (23)
300 to 6000 (12 to 236)
Replacement acoustic gel for standard transducers
Replacement acoustic gel for high-temperature transducers
Ordering Example: FDT-21W, wall mount transit-time ultrasonic flowmeter.