Jamar RAC Plus I, User Manual

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2-11
Once you have finished the following steps, your installation should
look similar to Figure 2-12 below.
Step 1 - Installing the Magnets
The number of magnets that must be used depends on the size of your tire and
where you mount the sensor. Most all installations on automobiles or trucks will
require at least six magnets (3 North/South Sets) to be installed. This will provide
3 pulses per revolution of the wheel or drive shaft to be sent to the Distance
Measuring Instrument (DMI).
On tractor or implement wheels the general
rule of thumb is one magnet for each wheel
bolt (minimum of two, and always an even
number). For drive shafts of small wheels
(ATVs), two magnets are usually adequate.
The magnets provided are marked with a
dashed line on the SOUTH pole side of the magnet, as shown in Figure
2-13.
Always use an even number of magnets, and always alternate the polarities
of the magnets as you go around the wheel hub or drive shaft.
Figure 2-12
Firewall
If possible, mount
Terminal Block
under dash inside
vehicle. Otherwise,
mount under hood in
convenient location
(left fender well)
to accommodate
necessary wiring.
K
H
Red
Green
Yello
w
Blac
k
Blac
k
White
Red
Ground
+12 VDC
Red
fuse
Sensor assembly
must not be mounted
more than 45 from
perpendicular
45" max.
Sensor
(Green
body)
3/8"
nuts
1/4" to 1/2"
air gap
1 " Minimum
1 " Minimum
Epoxy
Magnets to
Drive Shaft,
alternating
polarity.
N
S
N
N
S
S
Test magnet should alter-
nately attract and repel.
Magnets are marked
with a dashed line on the
SOUTH pole side.
Instrument black wire to battery ground and sensor black wire.
Instrument yellow wire to b12 VDC and sensor white wire.
Instrument green wire to sensor red wire.
Instrument red wire not used.
Cut end off of the Extension Cable (or the Magnetic Sensor cable
itself if the Extension Cable is not being used) and strip back the
insulation on the Red, White & Black wires. Attach to the terminal
block as shown.
J
I
G
F
D
A
S
N
North and South magnet sets must be evenly
spaced around the drive shaft, at least 1”
apart. Spacing between the North-South sets
is not as critical, but should be uniform.
DMI
Connector
S
N
Fig. 2-13
Chapter 2 — Installation