Dwyer NSS User Manual

Series NSS Non-Contact Speed Switch

NSS-A Shaft Speed Range

NSS-B Shaft Speed Range

3-1/8

(79.38)

2

-1/8

(53.98)

1-25/32
(45.24)

6-1/4

(158.75)

Ø1-17/32
(Ø38.89)

4-9/32

(108.74)

2-3/8

(60.33)

3-3/8

(85.73)

5-17/32
(140.49)

1

˝ NPT

Specifications - Installation and Operating Instructions

Bulletin L-32

NSSP

N

SSM

The Series NSS are self-contained rotation monitoring systems that are

ideal for detecting the unwanted slowdown of process equipment. These
systems bring efficiency and safety to your operations by preventing
machine damage, product waste and costly downtime. The non-contact
speed switch is commonly used to monitor drive trains, power-driven
components, crushers, exhaust fans, screw conveyors, or tail pulleys on
belt conveyors and elevators. The standard system includes either an
NSSM-series or an NSSP-series switch and a pulsar DISC.
Miniature speed switches contain a sensor and switching electronics in
either a heavy duty, explosion-proof cast aluminum housing (NSSM
series) or a chemical/corrosion resistant PVC housing (NSSP series).
Each switch is used with a shaft-end mounted pulsar DISC (or optional
split collar pulsar wrap) which generates an alternating magnetic field
that is picked up by the speed switch. The switch decodes this frequency
signal to determine shaft speed and compares this to the pre-adjusted
set point, easily calibrated via a single-turn potentiometer. In the event of
rotational failure, such as a broken drive, belt slippage, product overloads
or clogs, the relay can be used to provide an alarm or equipment
shutdown, assuring machine protection and process integrity. The
miniature speed switch series is fail-safe; any malfunction during
operation will de-energize the control circuit.
The primary difference between the NSSM/P and NSSM/P is the set
point range. The actual operating speed of the monitored shaft is not the
critical factor when selecting which model use, it is the desired set point
speed at which the relay is to energize and de-energize. The NSSM-A
and NSSP-A can be adjusted to trip from 10 to 100 rpm. The NSSM-B
and NSSP-B can be adjusted to trip from 100 to 5,000 rpm.

Principle of Operation:

The NSS-Series Switches contain a sensor and switching electronics
within the same housing. A pulsar disc, or an optional pulsar wrap,
rotating in front of the sensing surface produces a control signal which
increases with advancing shaft speed. When the control signal is above
the set point setting, the control relay is energized. When the control
signal drops blow the set point setting, the relay de-energizes. The relay
has Form C Dry contacts rated at 5 amps 115 Vac resistive, so the
NSSM may be used for switching motors and/or alarms.

Pulsar Disc:

The end of the shaft to be monitored must be center drilled to a depth of
1⁄2 inch with a No. 21 drill and tapped for 10-32 UNF. After applying
Loctite® or a similar adhesive on the threads to keep the pulsar disc
tight, the pulsar disc should be attached, decal side out, with the
supplied 10-32 UNF machine screw and lock washer.

SSP NSSM

N

SPECIFICATIONS
Temperature Limits: Operating -40 to 140ºF (-40 to 60ºC).
Enclosure: Cast aluminum. (NSSM); Polyvinylchloride (PVC) (NSSP).
Enclosure Rating: NSSM: Class I, Group D; Class II, Groups E, F, G;

Class III. NSSP: NEMA 4X.

Switch Type: SPDT.
Electrical Rating: 5A @ 115 VAC.
Electrical Connections: Terminal block.
Conduit Connections: 1˝ female NPT.
Power Requirements: 115 VAC, 60 Hz standard.
Input Signal Type: NPN Open Collector.
Set Point Adjustment: Single turn (270°) Potentiometer.
Gap Distance: 3/8˝ ± 1/8˝.

Pulsar Wrap (optional)

Pulsar Wraps are custom manufactured to fit the shaft they will be
mounted on. When the wrap is shipped, four allen-head cap screws hold
the two halves of the wrap together. These screws must be removed so
that the wrap is in two halves. Place the halves around the shaft, reinsert
the screws and torque them to 8 foot pounds.

Switch Selection Guide:

Refer to the Switch Selection Table, to determine which model is
appropriate for your application. The primary difference between the
NSSM/P and the NSSM/P is the set point range. The actual operating
speed of the monitored shaft can range from 10 to 5000 rpm with either
switch. The main criteria for selecting a speed switch is the speed at
which the relay energizes and de-energizes.
The NSSM/P can be adjusted to trip from 10 rpm to 100 rpm. The
NSSM/P can be adjusted to trip from 100 rpm to 5000 rpm.

Switch Selection Table:

NSS-A Adjustable Set Point Range 10-100 RPM

NSS-B Adjustable Set Point Range 100-5,000 RPM

PROXIMITY CONTROLS

A DIVISION OF DWYER INSTRUMENTS, INC.
P.O. BOX 373 • MICHIGAN CITY, INDIANA 46360, U.S.A.

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

Fax: [phone] e-mail: [e-mail]

Sensing Surface Gap Distance Table:

(See Figures 1 and 2, below)

Model No.

NSSM/P

NSSM/P

Note: The pulsar disc supplied with the NSSM/P switch is 4 inches in
diameter, and the NSSM/P disc is 2-1/2 inches in diameter.

Dimension “A” (inches)

1/4˝ ± 1/8˝

1/4˝ ± 1/8˝

Dimension “B” (inches)

1-3/4˝

7/8˝

Figure 1: Speed Switch with DISCA

Figure 2: Speed Switch with optional pulsar wrap

Wiring Diagrams:

These are typical wiring diagrams. Other circuits may be used and some
equipment may require different wiring.

Alarm only Circuit

Motor Shutdown Control without Alarm

Set Point Adjustment:

Complete the installation of the pulsar disc wrap and the speed switch
with the correct gap distance “A” before adjusting the set point. The unit
is shipped with the circuit potentiometer set for its lowest set point speed
(turned all the way counterclockwise). The potentiometer is a single-turn
type; turning it will make the device trip at speeds above the lowest setting
(See Fig. 3).

Calibration:

Remove the back cover of the speed switch. Apply 115 VAC power to the
speed switch on the black and white leads. With the shaft turning at
normal operating speed, turn the potentiometer clockwise until the relay
deenergizes. Turn the potentiometer counterclockwise 1⁄4-turn, which will
energize the relay. With this setting, the NSS Series Switch will
deenergize its relay when the shaft speed slows below normal operating
speed. Turning the potentiometer further counterclockwise will make the
unit less sensitive to a slowdown in speed. The green LED is illuminated
when the relay is energized.

Motor Shutdown with Alarm

Wiring Diagram Key

MS
OL

n.o.

TDR

Motor Starter (not supplied)
Overload contacts
Normally open (relay is in a deenergized state).
Time Delay “OFF” Relay (not supplied).
If the shaft being monitored comes up to speed slowly, a
TDR can be used so the operator will not have to hold the
START button in.

WARNING

During a stopped condition, even a slight movement of the shaft or
magnetic disc could energize the control relay and start the motor if the

Figure 3: Set Point Adjustment

©Copyright 2014 Dwyer Instruments, Inc. Printed in U.S.A. 5/14 FR# R6-443491-00 Rev. 1

PROXIMITY CONTROLS

A DIVISION OF DWYER INSTRUMENTS, INC.

Motor Auxiliary Normally Open Contact (MS Aus n.o.) is not wired in
series as shown in these typical diagrams. This situation could cause
equipment damage or PERSONAL INJURY! To prevent starting the motor
accidentally, ALWAYS USE PROPER LOCK OUT - TAG OUT
PROCEDURES.

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

Fax: [phone] e-mail: [e-mail]

P.O. BOX 373 • MICHIGAN CITY, INDIANA 46360, U.S.A.