Tachometers and Tach/Hourmeters
AT and ATH Series
Installation Instructions
IMPORTANT! These instructions are specific to tachometer
models with a power input operating range of 11-28 VDC and
calibration using dip switches. If your tachometer is a type using
selector switch calibration, please locate installation instructions
in the discontinued product literature section of the FW Murphy
Website (www.fwmurphy.com). Refer to Tachometer and
Tach/Hourmeter Installation Instructions Series: ATS, ATHS, ATA,
ATHA, ATHI (00-02-0258).
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BEFORE BEGINNING INSTALLATION OF THIS MURPHY PRODUCT:
A visual inspection of this product for damage during shipping is
recommended before installation.
It is your responsibility to ensure that qualified mechanical and electrical
technicians install this product.
Disconnect all electrical power to the machine.
Make sure machine cannot operate during installation.
Follow all safety warnings of the machine manufacturer.
Read and follow all installation instructions.
Please contact FW MURPHY immediately if you have any questions.
Table of Contents
General Information ......................................................................................................................... 1 Case Mounting Instructions ........................................................................................................... 2 Mounting Requirements ...................................................................................................2 Tools and Supplies Required for Installation ....................................................................3 Connection Instructions ........................................................................................................3 Typical Wiring Diagrams – Hookup for Magnetic Pickup .................................................3 Typical Wiring Diagrams – Hookup for Ignition ................................................................4 Typical Wiring Diagrams - Hookup for Alternator .............................................................4 Connecting to Power (All Models) ........................................................................................5 Installing or Replacing Light Bulbs (All Models) ...................................................................5 Connecting to Magnetic Sensor (Magnetic Sensor Driven Models) .....................................5 Connecting to Alternator (Alternator Driven Models) ............................................................5 Connecting to Ignition Coil (Ignition Driven Models) .............................................................5 Calibration Instructions ................................................................................................................... 6 Magnetic Sensor Driven Models ..........................................................................................6 Alternator Driven Models ......................................................................................................7 Pulley Ratios Chart and Alternator Tachometer Chart .....................................................8 Ignition Driven Models ..........................................................................................................9 Dip Switch Setting Charts ............................................................................................................. 10 Table 1 - Magnetic Sensor Driven Models ......................................................................... 10 Table 2 - Alternator Driven Models ..................................................................................... 13 Table 3 - Ignition Driven Models......................................................................................... 13 Specifications ................................................................................................................................. 14 Magnetic Sensor Driven Models ........................................................................................ 14 Alternator Driven and Ignition Driven Models ..................................................................... 14 General Information
These tachometers are indicators of engine speed, in revolutions per minute (RPM). Models
equipped with hourmeters also record elapsed engine running time. The hourmeter counts
when the engine speed is greater than 100 RPM.
For magnetic sensor (pickup) driven models, the pulses are obtained from the ring gear of an
engine flywheel (having from 50 to 304 teeth). Alternator driven models function from pulses
generated by the engine driven alternator that charges the battery. The alternator must have a
terminal for the tachometer.
Ignition models get their signal from the ignition system. This can be from the coil, or a
tachometer output from the ignition.
All units are for negative ground or isolated electrical systems. If the instrument is connected to
reverse polarity, it will not operate until proper connections are made. All units are powered by
a voltage range of 11 to 28 VDC.
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Case Mounting Instructions
It is preferred that the units are mounted in a place where they will be protected from rain and
splashing water. A minimum distance of 12 in. (305mm) from any coil, coil leads, or high
voltage wiring should be maintained. These units are intended for mounting on a flat panel with
a cut out of 3-3/8 in. (86mm), diameter hole as shown below. The maximum panel thickness
recommended is ½ in. (12.7mm). Remove the mounting bracket from the back of the unit.
Insert the instrument from the front side of the panel and place the mounting bracket to secure
the instrument in place.
Figure 1
Mounting Requirements
Figure 2 - Back of AT TACH
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Tools and Supplies Required for Installation
1.
11/32” and 3/8” Nut Drivers
2.
Wire Cutting & Stripping Tool
3.
Wire terminal Crimping Tool
4.
#10 crimp on ring terminals, and Faston™ or slip-on crimp terminals (for backlight)
ti )
Connection Instructions
CAUTION: For safety of both personnel and equipment, disconnect the
battery/power source before beginning installation.
Determine voltage and polarity of the application before wiring the unit.
Use the appropriate wire size. To wire the magnetic sensor pickup, use 18
AWG (1.0mm) twisted pair, shielded cable. Use insulated crimp-on
(solderless) ring-type wire terminals. Allow a few inches of extra wire
(service loops) for ease of servicing.
Typical Wiring Diagrams – Hookup for Magnetic Pickup
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Typical Wiring Diagrams – Hookup for Ignition
Typical Wiring Diagrams - Hookup for Alternator
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Connecting to Power (All Models)
IMPORTANT: The operating voltage range of these units is 11-28VDC
only. Always ensure circuits have a fuse or a circuit breaker to protect
wiring. Never connect the unit directly to a battery without a fuse or circuit
breaker.
1. Connect a wire from “+” to Battery or Power Supply “+” through a fuse and the ignition
switch.
2. Connect a wire from the "-" terminal to the negative voltage source (electrical
ground).This is shown in Figure 2 as the ‘ground stud’ (Figure 2 is found in the section:
Case Mounting Instructions under Mounting Requirements in this document).
Installing or Replacing Light Bulbs (All Models)
1. Pull out the black rubber protective cap (Light Assembly Cover) provided at back as
shown in Figure 2.
2. Twist the bulb holder about 1/8 turn counter-clockwise and remove the bulb holder and
bulb. (See Figure 2.)
3. To replace the bulb, pull the bulb from the socket and replace with a new 12V or 24V
bulb as required.
Connecting to Magnetic Sensor (Magnetic Sensor Driven Models)
The magnetic sensor (pickup) usually has two connections (terminals or wires) exiting from it.
These connections are not polarized; either connection can be considered positive or negative
signals. These two connections must be routed directly to the unit. Do NOT ground one of the
connections at the engine. (See Figure 2)
1. Connect one of the wires in the twisted pair (from magnetic sensor) to the “S” terminal.
2. Connect the other wire in the twisted pair (from the magnetic sensor) to the negative (-)
terminal (also noted in Figure 2 as the ‘ground stud’).
Connecting to Alternator (Alternator Driven Models)
Connect a wire from the “S” terminal to AC phase terminal (sometimes marked “STA” or “R” on
the alternator.
Connecting to Ignition Coil (Ignition Driven Models)
Connect wire from the “S” terminal to the negative (-) side of the ignition coil or to the terminal
marked “TACH” on solid state ignition systems (See Figure 2 – found in this document under
the section Case Mounting Instructions, Mounting Requirements).
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Calibration Instructions
Magnetic Sensor Driven Models
These models have been designed to function with flywheels having 50 to 304 teeth. Any
number in this range can be set using the dip switches provided on the back (see Figure 3 following). For more details, also refer to Table 1 (In the section: Dip Switch Setting Charts,
Magnetic Sensor Driven Models).
If the number of teeth on the flywheel is known, set the calibration by using a pin to adjust the
dip switches (see Figure 3, following).
IMPORTANT: DO NOT use a pencil or pen of any type to adjust dip
switches. If the pencil breaks while setting the dip positions, graphite can
cause a short internally. Leaking ink can do the same.
Formula for setting dip switches:
Dip switch setting = binary of decimal equivalent.
Decimal equivalent = number of flywheel teeth - 49.
NOTE: Dip switches D1 to D8 will be used for setting calibration.
Do not change settings on Dip Switches D9 and D10.
For more details refer to Table 1 - Dip Switch Setting for each model type.
NOTE: Make sure the engine has a properly functioning and certified
governor before attempting this procedure.
If the number of teeth on the flywheel is not known, set up a calibrated shop tach to monitor
the engine’s true RPM. Start the engine, and after an appropriate warm-up period increase to
normal running RPM as read on the shop tach. If the dip switch was not set previously, set it
now to the position that causes the Murphy tach to read closest to the true RPM.
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Alternator Driven Models
The alternator-driven tachometer-series models will operate from 3 to 255 pulses per engine
revolution. Most applications will be between 3 and 32 pulses per revolution. Obtain the
number of pulses per engine revolution:
1. Determine the number of poles on your alternator. Look for the designation/type in the
manufacturer’s manual.
2. The Alternator Tachometer Chart (Figure 4 – in the section: Pulley Ratios Chart and Alternator
Tachometer Chart) lists common alternators and their minimum and maximum pulley ratios. Determine
pulley ratio with the following formula:
PULLEY RATIO = CRANK SHAFT PULLEY DIAMETER
ALTERNATOR PULLEY DIAMETER
3. CHECK that Pulley Ratio falls within the range shown on the Pulley Ratio Chart (Figure 4) for a
particular alternator. If ratio falls in the shaded area, the tachometer can be calibrated for the
application.
4. To determine the pulses per engine revolution:
NUMBER OF POLES x PULLEY RATIO = PULSES PER ENGINE REVOLUTION
2
5. If the Pulses per engine revolution is determined, then set the calibration “through selector/dip
switches” (See Fig. 3 in the section: Calibration Instructions, Magnetic Sensor Driven Models).
6. Formula for setting Dip switches:
Decimal equivalent = No. of Pulses will be used for setting calibration
Dip switch setting = Binary of decimal equivalent
IMPORTANT
Dip switches D1 to D8 will be used for setting of calibration.
Do not change or disturb settings on Dip Switches D9 and D10.
For more details, see Table 2.
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Pulley Ratios Chart and Alternator Tachometer Chart
Figure 4
NOTE: * Although the tach may be calibrated for higher input frequencies
in some cases, as shown on the Pulley Ratios Chart, pulley ratios in
excess of 5.0 are not recommended nor are they normally used.
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Ignition Driven Models
The ignition coil-driven tach series models will operate from 1 to 5 pulses per engine
revolution. To obtain the number of pulses per engine revolution:
The ATI and ATHI series models have been designed to function from the
ignition signal on 2 through 10-cylinder, 4-cycle engines. Set the calibration using
the Dip switches. For more details, see the following formula and information in
Table 3 (in the section: DIP Switch Setting Charts, Ignition Driven Models).
Work the following formulas for your Ignition Coil system:
Formula for Setting Dip Switches:
Dip switch setting = Binary of decimal equivalent.
Decimal equivalent = Number of Pulses per engine revolution.
Number of Pulses per engine revolution = Number of engine cylinders
2
For Dip switch settings, please refer Table 3 (in the following section) for ignition speed
signals.
IMPORTANT: DO NOT use a pencil or pen of any type to adjust dip
switches. If the pencil breaks while setting the dip positions, graphite can
cause a short internally. Leaking ink can do the same.
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Dip Switch Setting Charts
Table 1 - Magnetic Sensor Driven Models
NOTE
In the following table, “1” means ON and “0" means OFF.
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Table 2 - Alternator Driven Models
NOTE: In the following table, “1” means ON and “0" means OFF.
NOTE: Switch combinations up to 255 pulses per revolution are not shown
as the range of 3 – 32 pulses per revolution fits most applications.
Table 3 - Ignition Driven Models
NOTE: Dip switches D4 through D8 are not used and should be set to
OFF.
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Specifications
Magnetic Sensor Driven Models
Power Input: 11-28VDC (70mA – 120mA except lamp load)
Backlight: 3.4W T-10 wedge base bulb
RPM Input Signal Voltage: 1.5Vrms minimum
Accuracy: Tachometer: +2% full scale
Hourmeter: +0.01% hours, +1 count
Temperature Range: -40oC to +82oC (no permanent damage shall occur)
Dial (Face Plate): 270o sweep with white numerals (over black background)
Bezel: 304 stainless steel for bright and IS 513 E.E.E. CRCA steel for black
Scale: 0-4000RPM
Case Material: Plastic
Hourmeter Range: 99999.9 hours in 0.1 increments.
Alternator Driven and Ignition Driven Models
Power Input: 11-28VDC (70mA-120mA except lamp load)
Backlight: 3.4W T-10 wedge base bulb
RPM Input Signal Voltage: V low: 0.5V max, V high: 8.0V min.
Accuracy: Tachometer: +2% full scale
Hourmeter: +0.01% hours, +1 count
Temperature Range: -40oC to +82oC (no permanent damage shall occur)
Dial (Face Plate): 270o sweep with white numerals (over black background)
Bezel: 304 stainless steel for bright and IS 513 E.E.E. CRCA steel for black
Scale: 0-4000RPM
Case Material: Plastic
Hourmeter Range: 99999.9 hours in 0.1 increments.
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MURPHY and the Murphy logo are registered and/or common law trademarks of Murphy Industries, Inc. This
document, including textual matter and illustrations, is copyright protected by Murphy Industries, Inc., with all
rights reserved. (c) 2011 Murphy Industries, Inc. Other third party product or trade names referenced herein are
the property of their respective owners and are used for identification purposes only.
CALL MURCAL TO PLACE YOUR ORDER
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