Murphy MTH6 User Manual

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Tachometer and Hourmeter With
Overspeed Shutdown or Alarm Switch

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3-1/2 Inches (89 mm) Diameter Dial

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Reads RPM Data from a Magnetic Pickup or
Battery Charging Alternator

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Powered by 8 to 40 VDC

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Large 5-Digit LCD Display

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Maintains Hours Count When Power Is Lost

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Front Panel Programming

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Hours Can Be Reset to Zero

Model MTH6

Description

This microprocessor-based digital tachometer
and hourmeter with a built-in overspeed
switch is highly accurate and dependable. It
measures speed and running hours and can give
an alarm or shut down the engine on
overspeed.

The MTH6 case is polycarbonate, and its dial
measures 3-1/2 in. (89 mm) in diameter.

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.

Applications

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,
also 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.

Specifications

Power Requirements:

8-40 VDC (12, 24 or 32 VDC systems).

Maximum Current:

12 VDC: 0.011 A, backlight Off;

0.025 A, backlight On.

24 VDC: 0.008 A, backlight Off;

0. 015 A, backlight On.

32 VDC: 0.007 A, backlight Off;

0. 010 A, backlight On.

Operating Temperature: -4° to 158°F

(-20° to 70°C).

Storage Temperature: -40° to 185°F

(-40° to 85°C).

Case: 1018 Polycarbonate/Polyester blend.
Mounting Hole Dim.: 3-3/8 in. (86 mm)

Dia.

Speed Input: 4.5 Vrms minimum.
Overspeed Switch Rating: 2 A, 50 VDC.
Overspeed Range: 0 to 9000 RPM.
Pulses per Revolution: 4 to 255.
Tachometer Range: 0 to 65,535 RPM.
Tachometer Accuracy: ±1% of the display

reading or -2 RPM whichever is greater.

Input Frequency Range: 25 Hz to 20 kHz.
Hourmeter Range: 0 to 99999 hrs.
Hourmeter Resolution: ±0.1 Hour up

to 9999.9; ±1 hour 10,000 and up.

Reset Hourmeter: Apply temporary ground to

terminal #5 to reset hours to zero.

Shipping Weight: 14 oz. (435 g).
Shipping Dimensions: 5-1/2 x 5-1/2 x

5-1/2 in. (140 x 140 x 140 mm).

•

Industrial Engines

•

Generators

•

Compressors

•

Oil Field
Equipment

•

Marine Engines

•

Vehicles

•

Farm Equipment

•

Construction
Equipment

MTH-96115B
Revised 02-04

Catalog Section 20

(00-02-0777)

Digital Tachometer and Hourmeter
With Adjustable Overspeed Set Point

Typical Wiring Diagram

MTH6 Back View

How to Order

Dimensions

Front View Side View Back View

Order by model designation:

MTH6 --

--

Bezel:

Blank = Bright Stainless

A = Black Stainless

Face Plate:

1 = White Background

http://www.fwmurphy.com

Find us on the internet:

MTH-96115B page 2 of 2

Warranty

A limited warranty on materials and workmanship is given with
this FW Murphy product. A copy of the warranty may be viewed
or printed by going to www.fwmurphy.com/support/warranty.htm

CONTROL SYSTEMS & SERVICES DIVISION

P.O. Box 1819; Rosenberg, Texas 77471; USA
[phone] fax [phone]

e-mail [e-mail]

MURPHY DE MEXICO, S.A. DE C.V.

Blvd. Antonio Rocha Cordero 300, Fracción del Aguaje
San Luis Potosí, S.L.P.; México 78384
[phone] fax [phone]
Villahermosa Office [phone]
e-mail [e-mail]
www.murphymex.com.mx

FRANK W. MURPHY, LTD.

Church Rd.; Laverstock, Salisbury SP1 1QZ; U.K.
[phone] fax [phone]
e-mail [e-mail]
www.fwmurphy.co.uk

MURPHY SWITCH OF CALIFORNIA

41343 12th Street West
Palmdale, California 93551-1442; USA
[phone] fax [phone]
e-mail [e-mail]
www.murphyswitch.com

In order to consistently bring you the highest quality, full featured products, we reserve the right to change our specifications and designs at any time.

MACQUARRIE CORPORATION

1620 Hume Highway
Campbellfield, Vic 3061; Australia
[phone] fax [phone]

e-mail [e-mail]

FW Murphy

P.O. Box 470248
Tulsa, Oklahoma 74147 USA
[phone]

fax [phone]
e-mail [e-mail]

www.fwmurphy.com

R

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USA–ISO 9001:2000 FM 28221

UK–ISO 9001:2000 FM 29422

Printed in U.S.A.

®

FRANK W.

MFR.

SETPOINT

MTH6

ENTER

15/32 in.
(12 mm)

3-5/8 in.
(92 mm)

Diameter

Mounting hole: 3-3/8 in. (86 mm)

3-1/8 in.
(79 mm)

Mounting

Bracket

Display

Light

Switch

3-33/64 in.

(89 mm)

Diameter

1

2

3

4

See

Note 1

--

Supply
8-40 Vdc

+

8

7

6

5

9

Note 2

3-9/16 in.

(90 mm)

®

FRANK W.

MFR.

1

2

3

4

5

9

8

7

6

CAUTION: Connecting full battery

potential to terminal 9 can cause damage
to the SWICHGAGE

®

. Shutdown circuit
is rated for 300 mA continuous.
Circuit grounds out at set point.

See Note 3

See

Overspeed Load 2 A, 50 Vdc
(example: 518PH TATTLETALE®
magnetic switches; SAH MINI-SIREN
TL7 Flashing Alarms)

®

;

NOTE 1: Apply momentary ground to reset

hours to zero.
NOTE 2: When using the MTH6 with inductive

loads, we recommend installing a
suppression diode across all coils.

NOTE 3: Terminals 4 and 8 may be grounded
on negative ground power supply.

NOTE 4: Alternator must be equipped with a
tach terminal (auxiliary AC terminal).

Shield

Grd.

Tachometer

terminal

See Note 4

Magnetic Pickup

Alternator