Dwyer FS User Manual

Bulletin # F-41-FS

Series FS Flowmeter with Limit Switch

Specifications - Installation and Operating Instructions

DESCRIPTION
Industrial

rugged, low cost, and simple to install. The Series FS
offers visual flow rate indication and an adjustable flow
alarm to open or close AC electrical circuits, trigger
warning lights, or activate other process control
equipment. Operating within ±5% of full scale accuracy,
the Series FS can be installed vertically or horizontally
without installing any special plumbing. The Series FS is
constructed of high impact resistant polysulfone. This
series offers excellent structural integrity against operating
pressures up to 325 psi (22.4 bar) for liquids and 125 psi
(8.6 bar) for gases. The Series FS can withstand fluid
temperatures up to 250°F (121°C) and is compatible with a
wide range of chemicals.

Direct-Reading Series FS Flowmeters are

OPERATING PRINCIPLE

The Series FS is a piston-type variable area flow meter
that uses a sharp-edged annular orifice formed between
an open-centered piston and tapered metering cone. the
piston is held in a “no flow” position at the base of the
cone by a precision retention spring. Flow through the
meter creates a pressure differential across the piston
orifice, moving the piston against the spring. Piston
movement and orifice area are proportional to the rate of
flow. Therefore, the greater the rate of flow, the further the
piston moves along the tapered metering cone. The flow
rate is measured by the viewing the red indicator ring
mounted on the piston relative to a graduated flow scale
affixed to the outer surface of the flow meter body.

MECHANICAL INSTALLATION

CAUTION: DO NOT OVER TIGHTEN THE THREADS ON
THE PLASTIC BODY. Overtightening the NPT threads may
cause fracturing of the plastic flowmeter body. The
flowmeter is constructed of polysulfone and remains
stable to 210°F (99°C). DO NOT EXPOSE FLOWMETER

PHYSICAL DATA

Accuracy: ±5% Full Scale.
Repeatability: 1.0%.
Set Point: Adjustable 0 to

100% FS.
Pressure Limits: 325 psi (22.4
bar)
Temperature Limits: 250°F
(121°C).
Supply Voltage: 115 VAC, 140
VAC max.

TO OPEN FLAMES OR EXCESSIVE HEAT. The meter may
melt, crack, or distort. Some pipe dope formulas will react

adversely with polysulfone. Use Teflon
material is necessary.

The Series FS can be mounted in any plane of orientation.
Horizontal or vertical mounting does not effect flowmeter
accuracy. The inlet and outlet of the flowmeter should be
aligned, particularly when high temperature, high
pressure, or a combination of both may be encountered.
Install the flowmeter in the direction of the indicating
arrow on the scale. The Series FS Flowmeter does not
require lengths of straight pipe at the inlet, or outlet, to
stabilize flow through the meter. These meters can
tolerate particles that normally will jam other flow controls.
If large amounts of particulates are encountered, a 200
mesh or 74 million micron filter is recommended.

A separate four conductor female connector is supplied
with the limit switch assembly. The connector must be
disassembled to solder wired onto it. See Figure 1. the
Connector has four solder lugs labeled 1, 2, 3, and 4.
Te rminals 3 and 4 are not used. It should be noted before
reassembly, which wire is connected to which solder plug.
Color coding or labeling the wires is advised. Secure

On-State Current: 0.02 to 1.0
A AC.
Connections: 1˝ male NPT
Polysulfone or
Brass.
Flow Scale: Calibrated at 1.0
specific gravity @ 70°F (21°C).
Wetted Materials: Polysulfone
body, Barium Ferrite, Stainless
Steel spring and retaining
rings.

3

/4˝ male NPT

®

tape as if sealing

DWYER INSTRUMENTS, INC.

P.O. BOX 373 • MICHIGAN CITY, INDIANA 46361, U.S.A. Fax: [phone] e-mail: [e-mail]

Phone: [phone] www.dwyer-inst.com

wires to solder lugs and determine the orientation A, B, or

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!

C, snap the connector back together, pull excess wires
out of strain relief, and tighten strain nut. Plug into electric
housing and secure with screw.

ELECTRICAL INSTALLATION

The module can only switch loads that consume between

2.5 and 90 watts, or have 5000Ω to 150Ω impedence
respectively. If the load draws less than 2.5 watts, a 0.47
uF loading capacitor is required. This capacitor will
increase the power consumption and ensure complete
conduction. See Figure 3. Wiring according to Figure 3
will provide conduction over 15-20% of full scale, above
or below the flow rate set point. For loads greater than 90
watts, see Figures 4 and 5.

CAUTIONS

WARNING: Due to incompatibility,

Polysulfone flow meters SHOULD
NOT be used for monitoring the
following fluids: ACETONE, ALCOHOL,
BENZENE, CARBON DISULFIDE, FREON 11,
KEROSENE, LIQUID PROPANE, NAPHTHA,
AND PERCHLOROETHYLENE.

Other chemicals may also be incompatible with
Polysulfone. When in doubt, the meter should be tested in
a non-critical application under low pressure conditions to
determine compatibility. Also note that some chemicals
become more aggressive when heated. An acceptable
application may become unsafe at elevated temperatures.

CAUTION: These flowmeters are unidirec­tional devices. The piston acts as a check
valve to block flow in the reverse direction,
causing an excessive pressure differential
which could result in damage to internal
components.

DWYER INSTRUMENTS, INC.

P.O. BOX 373 • MICHIGAN CITY, INDIANA 46361, U.S.A. Fax: [phone] e-mail: [e-mail]

Phone: [phone] www.dwyer-inst.com

CAUTION: Consult the factory before using

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any polysulfone meters to monitor the
following fluids: AMMONIA, ETHYLENE
GLYCOL 50/50, PHOSPHATE ESTER,
PHOSPHATE ESTER BASE, PHOSPHORIC
ACID.

PRESSURE DROP

FLOW-ALERT SWITCH OPTIONS

NOTE: All flow-alert switches are magnetically triggered.

Magnets cannot be added to the basic flow meter so it
is not possible to add a switch to the basic meter if it
was not originally ordered with the switching magnet.

SWITCH SPECIFICATIONS

Specifications AC Latching DC Latching

Operating

Voltage

Operating

Current

Contact

Rating

Operating

Tem p .

Cable

Certification

Enclosure

Rating

115 VAC ±10%

1A @ 30 VDC 0.5 @125 VAC

32 to 158°F (0 to 70 °C)

N/A

10-30 VDC

25 mA max

Resistive Load

Not Included

Reed Switch
Form-A (N.O.)

1A @ 200 VDC
Resistive Load

NEMA 12 &13 (IP65)

Reed Switch
Form-B (N.C.)

N/A

N/A N/A

32 to 250°F (0 to 125 °C)

3 ft., 24 ga 2 conductor PVC Jacket

Reed Switch
Form-C (SPDT)

N/A

0.25A @ 175 VDC
Resistive Load

CE

N/A

N/A

FLOW-ALERT LATCHING LIMIT SWITCH

The AC and DC powered low alert modules consist of
relay circuit housed in a sealed polypropylene enclosure.
The modules have a normally open dry relay contact that
can be used to directly control alarms, warning lights, and
relays or can be used to interface to a PLC. The relay will
be latched on as the magnet inside the flow meter passes
by the module and remained latched on until the magnet
passes in the other direction or power is interrupted (See
Figure 5). The set point is adjustable from 0 to 100% of
full scale. Flow meters can be equipped with one latching
limit switch, either AC or DC.

Figure 5
Latching Switches

FLOW-ALERT REED LIMIT SWITCH

The reed switch alert modules are available in three
forms. They are: Form A (Normally Open), Form B
(Normally Closed), and Form C (SPDT). Reed switches are
housed in a sealed polypropylene enclosure for
environmental protection. the reed switch modules do not
provide a latching function like the AC and DC powered
units. When the magnet inside the flow meter comes
within proximity of the module, the reed switch will

DWYER INSTRUMENTS, INC.

Phone: [phone] www.dwyer-inst.com

P.O. BOX 373 • MICHIGAN CITY, INDIANA 46361, U.S.A. Fax: [phone] e-mail: [e-mail]