MAIN-TACH

TACHOMETERS AND TACH/HOURMETERS

Series: ATS, ATA, ATHA, ATHS
3000 RPM – 0 to 100,000 Hours

Sensing from Magnetic Sensor Signal or Battery Charging Alternator
• High Visibility Analog Readout
• Air Core Movement
• Easy Calibration
• Through Dial Lighting
• Powered by 12 VDC Battery Converter for 24 to 12 VDC Available

Description

The tachometer is a rugged, transistorized instrument with solid-state circuitry for indication of engine revolutions per minute (RPM). It is equipped with a bracket for mounting into a standard 3-3/8 in. (86 mm.) dash mounting hole. The tachometer’s full 270° sweep of the pointer gives an accurate indication on a large easy–to–read scale. The dial can be illuminated for night reading. The models equipped with tachometer and hourmeter also record the elapsed running time of an engine.

Models for Alternator or Magnetic Sensor
These instruments are designed to function from pulses generated by an alternator with 4, 8, 12, 14 or 16 poles on the rotor, or the pulses can 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 70 to 225 teeth.

All models are for negative ground, positive ground or isolated electrical systems and are protected against reverse polarity hookup. If the instrument is connected reverse polarity, it will not operate until proper connections are made. The tachometer is powered by 12 VDC.

Description

Basic Models

Magnetic Sensor Signal Tachometer 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 Signal Tach/Hourmeter 70 – 225 pulses* 12 VDC

Model & Designation

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 3 – 27 pulses* 12 VDC

Model & Designation

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 Tachometer/Hourmeter 3 – 27 pulses* 12 VDC

Model & Designation

ATHA-30-12 Bright Stainless Steel Bezel
ATHA-30-12-A Black Stainless Steel Bezel
ATHA-30-12-B SAE Bright Stainless Steel Bezel
ATHA-30-12-C SAE Black Stainless Steel Bezel
ATVC12/24 24 to 12 VDC Converter

Specifications

Power Input: 12 VDC (11.5 – 16 V)
RPM Input Signal Voltage: 1.5 Vrms minimum from a magnetic pickup or alternator (minimum 3-pole)
Accuracy: Tachometer: ± 2% full scale Hourmeter: ± 0.01% hours, ± 1 count
Temperature Range: -5°F to 185°F (-20°C to +85°C)
Dial (Face Plate): 270° sweep with white numerals (over black background)
Bezel: 304 Stainless Steel
Scale: 0-3000 RPM
Case Material: Plastic
Hourmeter Range: Measures elapsed time: 100,000 hours in 0.1 increments (tenths)
Shipping Weight: 0.89 lb. (403 g)
Shipping Dimensions: 5-1/2 x 5-1/2 x 5-1/2 in. (140 x 140 x 140 mm.)

Warranty

A one-year limited warranty on materials and workmanship is given with this Murphy product. Details are available on request and are packed with each unit.

Determine if the tachometer or tachometer/ hourmeter can be used for your application

A. When used with magnetic sensor systems, the tachometer will operate from 70 to 225 tooth flywheels.
B. The alternator tachometer will operate from 3 to 27 pulses per engine revolution. Obtain the number of pulses per engine revolution for your |alternator system by working 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 / 2) x PULLEY RATIO = PULSES PER ENGINE REVOLUTION

ratios

ALTERNATOR TACHOMETER CHART

Manufacturer

Designation/Type

Poles

Minimum pulley-ratio

Maximum* pulley-ratio

Prestolite

All

8

0.75

6.5

Load Handler

88A, 8LHA, 89C, 8LHC

16

0.375

3.25

Load Handler

All 5 inch models

12

0.5

4.3

Leece Neville

All

12

0.5

4.3

Bosch

G and K Series

12

0.5

4.3

C.E. Neihoff

All

12

0.5

4.3

Delco Remy

30DN

4

1.5

13

Delco Remy

15SI, 21SI, 40DN, 40SI

12

0.5

4.3

Delco Remy

10DN, 10SI, 12SI

14

0.42

3.7

Delco Remy

20DN, 25SI, 27SI

16

0.375

3.25

Delco Remy

29SI, 30SI

16

0.375

3.25

Hitachi

LT125, LT130, LT133

8

0.75

6.5

Hitachi

LT150

12

0.5

4.3

Lucas

All

12

0.5

4.3

Mando

All

12

0.5

4.3

Motorcraft

All

12

0.5

4.3

Nippondenso

All

12

0.5

4.3

Powerline

Series 23

14

0.42

3.7

Powerline

Series 24, 25, 26

12

0.5

4.3

Valeo

All

12

0.5

4.3

* 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.

dimensionsHow to Order
Order the Tachometer or Tachometer/Hourmeter by model designation.

Example: ATA-30-12

ordering