FW MURPHY MP3298 Magnetic Pickup Instruction Manual
- June 13, 2024
- FW MURPHY
Table of Contents
FW MURPHY MP3298 Magnetic Pickup
Product Information
The Magnetic Pickup is an AC generator that is typically installed into the flywheel housing of an internal combustion engine. It generates a voltage pulse each time a gear tooth passes the end of the sensor, with the starter ring gear acting upon it. The pickup is available in three models: MP3298, MP7905, and MP7906.
Specifications
- 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: Two insulated leads, 20AWG, STR/TEF insulated per MIL-W-16878D Type E, 1 White and 1 Black.
- Output Voltage: 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: Internal portion of pickup is filled with epoxy resin, making the magnetic pickup oil and moist resistant.
Installation Instructions
- Magnetic Pickup Installation:
- Drill and tap a hole in the flywheel housing. Refer to the Specifications for the specific model and thread size.
- Important: Take care not to drill too deep as it may damage the ring gear teeth. Blow away chips with an air hose during drilling and tapping.
- Gap Adjustment:
- Insert the magnetic pickup into the hole and turn it until it stops at the face of the gear.
- Back-off the gear by turning the pickup counter-clockwise by 1/4, 1/2, or 3/4 turn (refer to the Gap Chart below).
- Note: The 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.
Ensure there are no metal chips on the magnetic tip if erratic readings occur. Always use a two-conductor shielded cable and ground the shield to a metal frame ground at the engine end only. Avoid running these wires next to spark plug wires or in wire loom with other wires carrying inductive loads or alternating current.
After adjusting, set the lock-nut to secure the magnetic pickup in place.
Additional Instructions
If you need to install a Tach Speed Switch, drill and tap the casing using the thread sizes specified in the Specifications section. The AC Meter reading must be taken at load.
GENERAL INFORMATION
WARNING
BEFORE BEGINNING INSTALLATION OF THIS MURPHY PRODUCT
- Disconnect all electrical power to the machine.
- Make sure the machine cannot operate during installation.
- Follow all safety warnings of the machine manufacturer.
- Read and follow all installation instructions.
Description
A 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.
Specifications
-
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.
Gap Chart
Typical Installation
-
Magnetic Pickup Installation (see diagram below)
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. -
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 (drawing right) . See Gap Chart below to determine gap distance based on the 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.
DIMENSIONS
-
A. MP3298 and MP7906= 3 in. (76 mm)
MP7905= 4.5 in. (114 mm) -
B. MP3298= 5/8-18 UNF-2A
MP7905 and MP7906= 3/4-16 UNF-2A -
C. MP3298= 0.250 in. (6 mm)
MP7905 and MP7906= 0.370 in. (9 mm)
Polarity: White lead is positive with respect to Black lead upon approach of ferrous metal.
Output Voltage Operating Chart
Note: Tested at 1000 I.P.S. 20 pitch gear 0.005 gap and 100K OHM load.
Gear Pitch/Voltage Output Chart
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
ABOUT COMPANY
- 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
- CONTROL SYSTEMS & SERVICES DIVISION
- P.O. Box 1819; Rosenberg, Texas 77471; USA
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- fax +1 281 633 4588
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- MURPHY DE MEXICO, S.A. DE C.V.
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- +52 444 8206264
- fax +52 444 8206336
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- Church Rd.; Laverstock, Salisbury SP1 1QZ; U.K.
- +44 1722 410055
- fax +44 1722 410088
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- 41343 12th Street West
- Palmdale, California 93551-1442; USA
- +1 661 272 4700
- fax +1 661 947 7570
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- www.murphyswitch.com
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- 1620 Hume Highway
- Campbellfield, Vic 3061; Australia
- +61 3 9358 5555
- fax +61 3 9358 5558
- e-mail murphy@macquarrie.com.au