FW Murphy Vibration, Time & Overspeed Gages

Prolonged engine vibration and shock can cause excessive wear to critical engine parts. Murphy builds a line vibration sensitive mechanisms that will shutdown your engine or electric motor powered equipment quickly. RJ Mann & Associates, Inc. stocks a wide inventory of mechanical timers, hourmeters and tachometers. Electronic switches for overspeed and magnetic pickups round out the category. FW Murphy builds other models that are not shown here. Please contact RJ Mann & Associates, Inc. inside sales to see which models are currently available.


Tachometers and Tach/Hourmeters: AT and ATH Series

murphy.ATHThe AT/ATH Series tachometers are rugged, transistorized instruments with solid-state circuitry for indication of engine RPM. They are equipped with a bracket for mounting into a standard 3- 3/8 in. (86 mm) dash mounting hole. A full 270° sweep of the pointer gives an accurate indication on a large easy–to–read scale and the dial can be illuminated for night reading. The ATH Series models are also equipped with an hourmeter to record the elapsed running time of an engine.

Models available for Alternator, Magnetic Sensor or Ignition signal. These instruments are designed to function from pulses generated by an alternator with 4, 8, 12, 14, or 16 poles on the rotor. The pulses can also be obtained from the ring gear of an engine by means of an electromagnetic sensor (magnetic pickup). Murphy’s magnetic sensor driven models are designed to function with flywheels having anywhere from 50 to 304 teeth. The Ignition signal model is available for 4, 6 or 8 cylinder, spark-ignited engines. All models are for negative ground, positive ground or isolated electrical systems and are protected against reverse polarity hookup.

All models are powered by an 11-28 VDC battery and are reverse polarity protected.


• 4000 RPM: 0 to 100,000 hours
• Sensing from magnetic sensor, battery charging alternator or ignition signal
• High visibility analog readout
• Air core movement
• Easy calibration through dip switches
• Through dial lighting
• Powered by an 11-28 VDC battery


These tachometers are specially designed for use on truck, marine, industrial, or stationary engines.


• Sales Bulletin (pdf)
• Installation Instructions: For models using a dip switch (pdf)
• Installation Instructions: For models using a selector switch (pdf)
• Potentiometer Fine Adjustment (pdf)
• Supplement: Magnetic Pickup Installation Instructions (pdf)

Selectronic® Digital Tachometer: MT90-1

murphy. MT90The Murphy Selectronic MT90-1 digital tachometer offers high accuracy and dependability resulting from use of a quartz crystal time based and digital, solid-state electronics.

Tachometer power is supplied by either a Murphy magnetic pickup, mounted at the flywheel ring-gear of an engine, or by a 12, 24 or 32 volt DC battery system.

RPM data is supplied by either a Murphy magnetic pickup or by the alternator in your battery charging circuit. The MT90-1 tachometer also has back-lighting for easy reading in low light areas; this lighting requires a battery power source.


• ±1 RPM accuracy
• Easy calibration
• Clear-read LCD display
• Back light for night viewing (battery powered models)
• Input source can be a magnetic pickup or engine alternator
• Power supplied by magnetic pickup or 12, 24, or 32 VDC battery system

RPM Calibration

The MT90-1 is calibrated to engine RPM by setting a series of calibration rotary switches on the back of the tachometer. The proper switch sequence for the engine is determined by:
• The number of ring gear teeth for the magnetic pickup
• The ratio of alternator to engine pulley diameter, and the number of poles of the alternator.


Typical applications include: Generators, Compressors, Industrial Engines, Oil Field Equipment, Marine Vessels, Vehicles, Farm Equipment, and Construction Equipment.


• Sales Bulletin / Installation Instructions (pdf)
• Supplement: Magnetic Pickup Installation Instructions (pdf)

Digital Tachometer and Hourmeter: MTH6

murphy. MTH6The MTH6 is a microprocessor-based digital tachometer and hourmeter with a built-in overspeed switch. The 3-1/2 in. (89 mm) diameter, polycarbonate case houses an instrument that is highly accurate and dependable. It measures speed and running hours and can give an alarm or shut down the engine on overspeed.

RPM data for the tachometer and overspeed switch is supplied by a magnetic pickup or battery charging alternator. The magnetic pickup is installed into the flywheel housing of an internal combustion engine. The starter ring gear acts upon the magnetic pickup to generate a voltage pulse each time a gear tooth passes the end of the sensor.


• Tachometer and hourmeter with overspeed shutdown or alarm switch
• 3-1/2 inches (89 mm) diameter dial
• Reads RPM data from a magnetic pickup or battery charging alternator
• Powered by 8 to 40 VDC
• Large 5-digit LCD display
• Maintains hours count when power is lost
• Front panel programming
• Hours can be reset to zero

Basic Operation

During normal operation, the MTH6 displays RPM. Its five-digit, liquid crystal display is updated every second. When the MTH6 is displaying hours and a speed signal is present, the far left digit and decimal point will flash indicating the hourmeter is operating. The overspeed set point and running hours can be viewed by manipulating three membrane switches located on the MTH6 front panel. When the overspeed set point is met, an LED located on the front panel lights.

Easy Calibration

The MTH6 calibration is simple. The operator enters the number of pulses per engine revolution and the overspeed set point value using the membrane-switches located on the front of the MTH6.


Typical applications include: Generators, Compressors, Industrial Engines, Oil Field Equipment, Marine Vessels, Vehicles, Farm Equipment, and Construction Equipment.


• Sales Bulletin (pdf)
• Installation Instructions (pdf)
• Supplement: Magnetic Pickup Installation Instructions (pdf)

Magnetic Pickups

murphy. magnetic pickupsA magnetic pickup is an AC generator. It is normally installed into the flywheel housing of an internal combustion engine, so that the starter ring gear acts upon it to generate a voltage pulse each time a gear tooth passes the end of the sensor.

Magnetic Pickup Installation
Drill and tap a hole in the flywheel housing (See Specifications for model and thread size). IMPORTANT: Drilling too deep may damage ring gear teeth. Blow chips with air hose when drilling and tapping hole. Download the Installation Instructions for gap chart, dimensions and diagrams.

Gap Adjustment
Insert magnetic pickup and turn until it stops at the face of the gear. Back-off the gear by turning the pickup counter-clockwise 1/4, 1/2, or 3/4 turn. Check gap clearance by rotating the gear completely around. NOTE: Magnetic pickup gap should be adjusted so that the minimum voltage required is attained at the engine’s lowest RPM. The voltage will increase as the speed increases. If erratic readings occur, remove magnetic pickup and check the magnetic tip for metal chips.


Housing Material:
     MP3298: Type 300 Stainless Steel     Locknut: Type 300 Stainless Steel
     MP7905 and MP7906: Type 6061 Aluminum/Anodize Class 1     Locknut: Steel Nickel Plated

Output Leads (all models): Two insulated leads, 20AWG, STR/TEF insulated per MIL-W-16878D Type E, 1 White and 1 Black

Output Voltage (all models): 200 V.P.P. TYP. (tested at 1000 I.P.S. 20 Pitch gear, 0.005 Gap., and 100K OHM Load)

Coil Resistance:
     MP3298: 975 Ohms TYP
     MP7905 and MP7906: 2500 Ohms TYP

Potting (all models): Internal portion of pickup is filled with epoxy resin, making the magnetic pickup oil and moist resistant.

Temperature (all models): -65° to +225°F (-54 ° to 107°C)

Coil Induct.:
     MP3298: 800 mH max, @ 1K Hz.
     MP3298: 400 mH TYP. @ 1K Hz.


• Installation Instructions (pdf)

Digital Tachometer and Hourmeter: SHD30 and SHD30-45

murphy. SHD30The SHD30 and SHD30-45 are microprocessor-based tachometers with an hourmeter and an overspeed trip point. The trip point can be connected as either a form “C” relay output or as a normally open SCR output for alarm or shutdown on over-speed. The SHD30 features a panel-mounting, plastic enclosure that is 5-1/16 in. (129 mm) long and 4-1/4 in. (108 mm) high. The SHD30-45 has the same enclosure, but it also has a backplate with studs to mount like a SHD-45, OPLFC.

Power and RPM data are supplied by either a magnetic pickup or a capacitor discharge (CD) ignition. The hourmeter is adjustable to a preset time and resettable to zero. Should power be lost, on-board batteries maintain the run hours display and allow for resetting the overspeed relay output. When a tach signal is present, the SHD30 models display RPM. When a tach signal is not present, the display is blank unless the Read Hours membrane key on the faceplate is pressed and held.

The five-digit, liquid crystal display is updated every second. The run hours, overspeed set point and current pulses per engine revolution can be displayed by manipulating the membrane switches. Run hours can be displayed even after power is lost. The run hours display can be configured to alternate with the RPM display.


• Normally open and normally closed overspeed alarm or shutdown switch (standard)
• RPM data and power supplied by magnetic pickup or capacitor discharge (cd) ignition
• Accurate to ±0.5% of display reading
• Hours can be preset and reset to zero
• Approved for Class I, Division 2, Groups C & D hazardous areas


Calibration is done by entering the number of pulses per engine revolution using the Pulses per Revolution and Overspeed Setpoint membrane keys on the faceplate. The number of pulses is determined by the number of cylinders, cycles and ignition features. It is also determined by the number of ring gear teeth of the engine’s flywheel on a magnetic pickup system. Presetting and resetting running hours can be done from both the front and back of the instrument.


Gas Compressors, Oil Field Equipment, Industrial Engines, Generators


• Sales Bulletin (pdf)
• Installation Instructions (pdf)
• Installation Diagram (pdf)
• Supplement: Magnetic Pickup Installation Instructions (pdf)

Electronic Speed Switches: HD9063 Series, OS77D Series and SS300 Series

murphy. OS77DHD9063 Series
The HD9063 Series is a unitized two set point speed switch with SPDT relay outputs. A PC-board configuration with standoffs for mounting in a control panel or cabinet. The HD9063 provides crank disconnect and overspeed functions. Trip points can be field adjusted on all models. LED’s next to the set point potentiometers indicate that the trip point has been reached and the relay(s) have operated. The built-in overspeed test circuit will actuate the output relay at a point 10% below the actual overspeed set point.

Crank disconnect/overspeed model is typically used to disconnect the starter on automatic start engine applications and to shutdown the engine if an overspeed situation occurs. Re-engagement of the starter is inhibited until RPM returns virtually to zero. Typical applications include: standby generator sets, pumps and compressors.

• Sales Bulletin (pdf)
• Installation Instructions (pdf)
• Supplement: Magnetic Pickup Installation Instructions (pdf)

OS77D Series
The OS77D Series single set point speed switch is a compact all-electronic speed sensing module. It can be panel mounted via its trip set point potentiometer. It is field adjustable and gives a transistor output when tripped. Relay models are available. Models are available with Normally Open or Normally Closed circuit and with or
without re-crank feature which inhibits starter re-engagement until the engine speed is near zero RPM.

• Overspeed shutdown: Activates engine shutdown circuit on engine overspeed.
• Operate PTO's or drive circuits: Engage or disengage engine PTO, 4-wheel drives, or other control circuits according to RPM monitored.
• Disconnect engine cranking when engine starts.

• Sales Bulletin (pdf)
• Installation Instructions (pdf)
• Supplement: Magnetic Pickup Installation Instructions (pdf)

SS300 Series
The SS300 Series are single set point speed switches with SPDT relay dry contact output. The trip point is set by a potentiometer. An LED indicates when the signal source is present. A second LED turns on when the trip point is reached. An optional time delay is on board to delay operation of the relay for 2-6 seconds after the set point has been reached. The SS300 Series speed switch is intended for installation within a weather-proof enclosure to protect it from rain, dust, etc.

• Overspeed shutdown: Shuts down the engine if RPM exceeds the pre-set limit.
• Speed sensitive pull-in/drop-out: Engage or disengage PTO’s, 4-wheel drives, and other switch points according to speed of engine being monitored.
• Engine and transmission alarms/shutdowns: Oil pressure in some engines and transmissions varies widely between running and idle speeds. The SS300 Series can select between two pressure switch set points according to speed of the engine or transmission and thus give maximum protection to the equipment while at operating RPM and eliminate nuisance alarms when at idle.
• Adjustable differential model: The (“AD”) can be adjusted to change the speed range over which the pull-in and drop-out differential of the relay will operate.
• A typical application is to insure that engine speed is above a minimum RPM before applying a load but allows a drop in speed of several hundred RPM without disconnecting the load.

• Sales Bulletin (pdf)
• Installation Instructions (pdf)
• Supplement: Magnetic Pickup Installation Instructions (pdf)

Hourmeters: TM Series

murphy. TM4594TM Series hourmeters record the operating time of vehicles or powered equipment. They are electromechanical and have a quartz base time counter that insures accuracy (better than ±0.02% over the entire range). They can record up to 99,999.9 hours (9,999.9 for TM612/624) and include an automatic recycle to zero hours feature. TM Series models have a shock-proof and tamperproof, totally sealed case made of high-impact engineered plastic. These small, lightweight time meters are rugged and durable. They are the answer to applications requiring a low DC power combined with a reliable hourmeter. The TM612/624 model includes a 3-hole mounting shock ring for extreme shock protection.


• 2 in. (51 mm) diameter dial
• Mechanical counter – no battery needed to maintain elapsed time
• Reversed polarity protected
• Quartz-crystal time base for accurate long-term timekeeping
• Powered by 12 to 24 VDC
• Solid-state electronic drive circuit
• Quiet operation – permanently lubricated
• High-impact, tamperproof, environmentally sealed plastic case
• Indicates operating time in hours and tenths
• No battery back-up required


These hourmeters can be used on any engine where operating time needs to be recorded. All it requires is a DC power source.


• Sales Bulletin (pdf)

Time Switches: 5T, 15T, 12T and 24T

murphy.5TMurphy Time Switches can automatically start or stop engines or electrical motors after a pre-determined time. These time switches can be wired for a open or closed circuit when time expires. They require no electrical current to operate and have an SPDT contact arrangement. These switches feature a precision movement that gives years of reliable service. A built-in stop prevents overwinding. 

The 12T (12 hour) and 24T (24 hour) time switches are enclosed in a NEMA 4 weatherproof enclosure. A hinged, gasketed cover and 1/2 NPT conduit connection allow for a dust-tight installation. The enclosure includes a clasp and eye for padlock to prevent unauthorized operation. Instructions for popular engine applications are secured inside of the lid.

The 5T (5 minute) and 15T (15 minute) timers mount directly in control panels for short range timing with manual reset. These switches are perfect for disconnecting shutdown circuits while equipment is being started.


• Two versions available:
      • Hour switch for setting run time and shutdown of equipment
      • Minute switch for a short interruption of Swichgage® circuits on test or start-up
• Spring wound, no electric power required
• Precision movement can be set to zero at any time
• Built-in stop prevents overwinding


Murphy Time Switches are designed for use in the oil field, irrigation systems or anywhere equipment must operate or be controlled for a predetermined time. Mounted on a post or in a panel away from vibration and shock, these time switches give accurate, long term service.


• Sales Bulletin / Installation Instructions (pdf)
• Supplement: Magnetic Pickup Installation Instructions (pdf)

EVS: Electronic Vibration Switch

murphy.EVSMurphy's new Electronic Vibration Switch (EVS) protects against equipment failure by monitoring velocity-based vibration levels and providing an early warning or shutdown when abnormal vibration is detected. The EVS product can be connected to Murphy’s TTD™ annunciator, Centurion™ or Millennium™ controllers for increased functionality.

This instrument also complements Murphy’s VS2™ shock and excessive vibration/pulsation switch, which is designed to detect an abnormal shock or pulsation due to equipment failure and to shutdown other equipment in a system to prevent further damage. An optional internal battery powered EVS switch model is also available, designed for use on ignition powered systems.

The EVS can be used on any equipment where abnormal vibration could lead to equipment damage, including cooling fans, engines, pumps, compressors, gear boxes, motors and generator sets.

The EVS can monitor and alert the operator of abnormal vibration caused by a variety of possible factors, including imbalance and misalignments, defective sleeve bearings, broken tie down bolts, defective ball or roller bearings, gear mesh, blade pass frequencies, detonation and broken parts.


• Piezoelectric-crystal internal sensor with built-in microelectronics for reduced noise sensitivity
• Electronically integrated output signal that measures and trips on velocity
• Adjustable calibrated set-point controls
• Shutdown set-point measured in velocity
• Optional 4-20 mA output for continuous monitoring capability
• Solid-state outputs for setpoint trip
• Adjustable time delay prevents false tripping on high-vibration start-up/non-repetitive transient events
• Self-test and calibration


• Sales Bulletin (pdf)
• Installation Instructions (pdf)

Shock and Vibration Switch: VS2 Series

murphy.VS2The VS2 Series switches are shock sensitive mechanisms for shutdown of engine or electric motor powered equipment. These switches use a magnetic latch to ensure reliable operation. Explosion-proof “EX” models for hazardous locations are available.


VS2 and VS2C
The VS2 and VS2C are designed for use in non-hazardous locations. They have leaf-type SPDT, double make contacts that can be used for shutdown and/or alarm. They have a slotted sensitivity adjustment located on the side of the case.

Model VS2EX is housed in an explosion-proof enclosure with threaded cover. This enclosure is CSA and UL listed for Class I, Division 1, Groups C & D hazardous locations. In place of the leaf type contacts, 2-SPDT snap-switches are used in this model. Sensitivity is externally adjustable and, when tripped, the VS2EX gives a Tattletale® indication on the reset button. It is constructed to meet NEMA 7 specifications.
     • NEMA 7/IP50 Specifications
     • Snap-switch Contacts
     • Tattletale® Reset Button

Model VS2EXR features an electric remote reset feature in addition to the Tattletale® reset button. The VS2EXR uses only one SPDT snap-switch and is CSA and UL listed for Class I, Division 1, Groups C & D hazardous locations. It is constructed to meet NEMA 7 specifications.
     • Remote Reset Feature
     • NEMA 7 Specifications
     • Snap-switch Contacts
     • Tattletale® Reset Button

Model VS2EXRB is constructed for use in Class I, Division 1, Group B, hazardous locations. It has, as standard, a SPDT snap-switch and an electric remote reset. Option is available for DPDT snap-switch.
     • For Group B Locations
     • Snap-switch Contacts
     • DPDT Feature Optional


Ideal for use on engines, pumps, compressors, heat exchangers and pumping units, the VS2 Series can be used anywhere shutdown protection from damaging shock/vibration is desired. Switches are field adjustable to sensitivity required in each application.


• Sales Bulletin (pdf)
• Installation Instructions (pdf)

© 2016  RJ Mann & Associates Inc.