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How to Determine if the Tachometer or Tach/
Hourmeter is Suitable for Your Equipment
A. Ignition sensing Tach/hourmeters can be used on 4, 6 or 8 cylinder, spark
ignited engines.
B. Magnetic pick up sensing Tachometer or Tach/hourmeters will operate from
70 to 225 tooth flywheels.
C. Alternator sensing Tachometer or Tach/hourmeters will operate from 3 to 27
pulses per engine revolution. To obtain the number of pulses per engine revo-
lution, work the following formulas:
1. Determine the number of poles on your alternator. Look for the
designation/type in the manufacturer's manual or remove the
pulley and fan to count the number of poles on the rotor.
2. The 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 RATIOS CHART 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
ALTERNATOR TACHOMETER CHART
Manufacturer Designation/Type Poles
Minimum Maximum
*
pulley-ratio pulley-ratio
*
Although the tach may be calibrated for higher input frequencies in some cases, as shown on the
Pulley Ratio chart, pulley ratios in excess of 5.0 are NOT recommended nor are they normally used.
Prestolite
Load Handler
Load Handler
Leece Neville
Bosch
C.E. Neihoff
Delco Remy
Delco Remy
Delco Remy
Delco Remy
Delco Remy
Hitachi
Hitachi
Lucas
Mando
Motorcraft
Nippondenso
Powerline
Powerline
Valeo
All
88A, 8LHA, 89C, 8LHC
All 5 inch models
All
G and K Series
All
30DN
15SI, 21SI, 40DN, 40SI
10DN, 10SI, 12SI
20DN, 25SI, 27SI
29SI, 30SI
LT125, LT130, LT133
LT150
All
All
All
All
Series 23
Series 24, 25, 26
All
8
16
12
12
12
12
4
12
14
16
16
8
12
12
12
12
12
14
12
12
0.75
0.375
0.5
0.5
0.5
0.5
1.5
0.5
0.42
0.375
0.375
0.75
0.5
0.5
0.5
0.5
0.5
0.42
0.5
0.5
6.5
3.25
4.3
4.3
4.3
4.3
13
4.3
3.7
3.25
3.25
6.5
4.3
4.3
4.3
4.3
4.3
3.7
4.3
4.3
How to Order
Order the Tachometer or Tachometer/Hourmeter by model number.
Magnetic Sensor Tachometer 3000 RPM; 70 - 225 pulses 12 VDC
Model # Designation
ATS-30-12 Bright Stainless Steel Bezel
ATS-30-12-A Black Stainless Steel Bezel
ATS-30-12-B SAE Bright Stainless Steel Bezel
ATS-30-12-C SAE Black Stainless Steel Bezel
Magnetic Sensor Tach/Hourmeter 3000 RPM; 70 - 225 pulses 12 VDC
ATHS-30-12 Bright Stainless Steel Bezel
ATHS-30-12-A Black Stainless Steel Bezel
ATHS-30-12-B SAE Bright Stainless Steel Bezel
ATHS-30-12-C SAE Black Stainless Steel Bezel
Alternator Signal Tachometer 3000 RPM; 3 - 27 pulses 12 VDC
ATA-30-12 Bright Stainless Steel Bezel
ATA-30-12-A Black Stainless Steel Bezel
ATA-30-12-B SAE Bright Stainless Steel Bezel
ATA-30-12-C SAE Black Stainless Steel Bezel
Alternator Signal Tach/Hourmeter 4000 RPM; 3 - 27 pulses 12 VDC
ATHA-40-12 Bright Stainless Steel Bezel
ATHA-40-12-A Black Stainless Steel Bezel
ATHA-40-12-B SAE Bright Stainless Steel Bezel
ATHA-40-12-C SAE Black Stainless Steel Bezel
ATHA-40-12-A Black Stainless Steel Bezel
Ignition Signal Tach/Hourmeter 4000 RPM; 4, 6 or 8 cylinder 12 VDC
ATHI-40-12-A Black Stainless Steel Bezel
Optional Power Input Convertor
ATVC12/24
24 VDC to 12 VDC Converter
3-53/64 in.
(97 mm)
3-5/8 in.
(92 mm)
21/32 in.
(17 mm)
3-3/8 in. min.
(86 mm)
Mounting Hole
RPM
x 100
HOURS
1
10
Dimensions
0.5 1.5
2.0 2.5
3.0
3.5
4.0
4.5
5.0
4
8
12
14
16
PULLEY RATIOS CHART
NO. OF POLES
1.5 —– 13
0.75 —– 6.5
0.5 —– 4.3
0.42 —– 3.7
0.375 —– 3.25
RATIO
Minimum Maximum
TAH-97026B 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
INDUSTRIAL PANEL DIVISION
P.O. Box 470248
Tulsa, Oklahoma 74147 USA
+1 918 317 4100 fax +1 918 317 4266
e-mail sales@fwmurphy.com
MURPHY DE MEXICO, S.A. DE C.V.
Blvd. Antonio Rocha Cordero 300, Fracción del Aguaje
San Luis Potosí, S.L.P.; México 78384
+52 444 8206264 fax +52 444 8206336
Villahermosa Office +52 993 3162117
e-mail ventas@murphymex.com.mx
www.murphymex.com.mx
FRANK W. MURPHY, LTD.
Church Rd.; Laverstock, Salisbury SP1 1QZ; U.K.
+44 1722 410055 fax +44 1722 410088
e-mail sales@fwmurphy.co.uk
www.fwmurphy.co.uk
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.
FW Murphy
P.O. Box 470248
Tulsa, Oklahoma 74147 USA
+1 918 317 4100 fax +1 918 317 4266
e-mail sales@fwmurphy.com
www.fwmurphy.com
Printed in U.S.A.