Electronic Programmable
Speedo (EPS)
Introduction
The EPS is a universally
applicable product. No matter what
the source of the speed input signal,
the size of wheels or tyres or the
final drive ratio of the gearbox
being used, our product can be
programmed by you to work within the
legal limits.
IMPORTANT INFORMATION
- Only to be fitted to Negative
Earth Vehicles.
- Disconnect your
vehicle’s battery prior
to installation
- Operating Voltage between 11
and 17 volts DC – NB the
speedometer is fitted with a
12V lamp.
- The speedometer complies with
CE regulations regarding
electromagnetic
compatibility.
Input Signals
The EPS can accept input signals
from:-
- OUR RECOMMENDED SOLUTION
- A magnetic sensor
- using a reed switch
positioned so as to be able
to count the revolutions of
the prop shaft, half shaft or
the road wheels. This is
achieved by attaching a
number of magnets (usually 4)
to the prop shaft, the half
shaft or the inner surface of
the road wheel. The sensor
registers the change in
magnetic field which occurs
each time a magnet passes it.
Each time a change in
magnetic field is sensed a
signal or pulse is
transmitted to the
speedometer. CAI
offers a universal speed
sensor kit, consisting of the
sensor itself and 6 magnets.
The installer then has to
provide a mounting bracket,
to position the sensor and
fix the magnets (on prop
shaft installations 4 is the norm) using a 24hour 2 part
epoxy adhesive. For speed
sensor installation
instructions just follow the link, speed sensor installation
- A magnetic proximity
sensor positioned so
as to be able to count the
revolutions of the prop shaft
or the road wheels. If
counting prop shaft
revolutions, then the sensor
should be positioned parallel
to the prop shaft, close to
the universal joint, either
where the prop shaft exits
the gearbox or enters the
differential. The idea is
that the sensor should be
able to detect the passing of
the bolts on the universal
joint. If counting road wheel
revolutions, then the sensor
should be at right angles to
the wheel and could detect
either passing wheel nuts or,
on more modern vehicles, the
cooling slots in the brake
disks. The sensor detects the
change in magnetic field
created by the a the passage
of a steel bolt or a slot in
a brake disk. Each time the
change in magnetic field is
sensed a signal or pulse is
transmitted to the
speedometer. CAI offers a
proximity sensor as an
accessory under the part
number EMP24-1
- A hall effect sensor, these are used in vehicles where
the gearbox has the provision
for a mechanical speedo cable
take off, The hall effect
sensor fixes into the speedo
take off point and counts the
revolutions of what would
have been the cable drive.
- The EPS will also accept
signals directly from the electronic
control unit of the
vehicle’s engine
management system, if fitted.
Programming Your EPS
- Disconnect the battery.
- Make sure your vehicle is
negative earth.
- Calculate you calibration
number: - N.B. For most of
the following calculations
you will need to know the
number of times that your
tyre revolves per mile or
kilometre. If you do need
this information for your
installation then stand the
vehicle on a flat surface and
make a mark on a tyre, mark
the floor at the same point.
Move the vehicle forward for
one revolution of the tyre
and measure the distance
covered. You can then figure
out how many times the tyre
would revolve in covering a
mile or a kilometre.
- Magnetic Sensor
- using a reed switch
using prop shaft
revolutions, Number of
magnets x differential
ratio x tyre revs per
mile or per kilometre =
calibration number
- Magnetic Sensor
- using a reed switch,
using half shaft or wheel
revolutions, Number of
magnets x half shaft or
wheel revolutions per
mile or per kilometre =
calibration number
- Magnetic
Proximity Sensor
- using prop shaft
revolutions, Number of
bolts at the universal
joint x differential
ratio x tyre revs per
mile or kilometre =
calibration number
- Magnetic
Proximity sensor
- counting brake disk
slots or wheel nuts,
Number of wheel nuts or
slots x tyre revs per
mile or kilometre =
calibration number.
- Hall effect
sensor, Number of
poles on sensor x cable
drive revs per mile or
kilometre = calibration
number.
- Electronic
Control Unit,
number of pulses per mile
or per kilometre as
declared by the engine
manufacturer =
calibration number.
- Convert your calibration
number into a calibration
switch setting using the
attached table.
- Set the calibration switches.
The calibration switches are
a series of 10 switches to be
found on the rear of the
instrument under the large
rubber grommet, remove the
grommet by pressing above the
centre and inserting a small
coin or screwdriver under the
raised lip and popping out
the grommet. The 10
calibration switches have to
be switched either on or off.
On is indicated by a 1 on the
switch settings, off by a
zero.
For example,
Calibration number 18142 =
switch setting
| 1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
| 0 |
0 |
0 |
1 |
0 |
0 |
0 |
0 |
0 |
1 |
| off |
off |
off |
on |
off |
off |
off |
off |
off |
on |
For the Calibration Number Table
follow the link below:
CALIBRATION
TABLE
Installation Of Your EPS
- A hole is needed in the
fascia panel (the size will
depend upon the diameter of
speedometer being fitted),
with sufficient clearance
behind it to accept the body
of the speedometer.
- Check again that the battery
is disconnected.
- Wire the instrument as
follows: -
- Green Wire
– live feed to the
speedometer
- Black Wire
– earth (ground)
connection
- Brown/Slate
Wire – Only
to be connected if you
wish the LCD Odometer to
be visible with ignition
off. If required connect
to a live feed.
- Red/White Wire
– power for the
speedometer lamp, connect
to a dash lighting power
feed.
- Red Wire
- only needed if using a
hall effect sensor,
connect to a live feed.
- White/Black
Wire –
connection for speed
signal input from the
hall effect sensor or
Electronic Control Unit
or Magnetic sensor using
a reed switch.
- Red/Blue Wire
– connection for
speed signal input from a
magnetic proximity
sensor.
- Light Green/Purple
Wire –not
used in this application.
- The speedometer can now be
installed in the fascia panel
hole and clamped against the
rear of the panel using the
fixing clamp, spring washers
and knurled nuts supplied.
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