Bendix Commercial Vehicle Systems WS-24 ANTILOCK WHEEL SPEED SENSOR - Manual (Page 2)

2
ANTILOCK CONTROLLER
& RELAY
WS-24 ™ SPEED SENSORS
EXCITER
WHEELS
FRONT WHEEL
REAR WHEELS
The number of AC cycles per revolution of the vehicle's
wheel depends on the number of teeth in the exciter, which
is programmed into the antilock controller. Using the
programmed data, the controller can calculate "vehicle
speed" by analyzing the frequency of AC cycles sent by the
speed sensor. (The frequency of AC cycles is directly
proportional to wheel speed.) See Figure 4.
AC voltage is also proportional to speed, but voltage is not
used to determine speed. It is only an indication of AC
signal strength. The amount of AC voltage generated by a
specific speed sensor depends on the distance, or "gap"
between the tip of the sensor and the surface of the exciter.
Voltage increases as the sensor gap decreases.
Typically, the WS-24 ™ sensor is installed in mounting blocks
that are welded to the axle housing. (See Figure 2.)
WS-24
™ wheel speed sensors are protected by a stainless
steel sheath. They are designed to be used with beryllium-
copper clamping sleeves (sometimes referred to as a
“retainer bushing”, “friction sleeve” or “clip”) (See Figure 3).
The clamping sleeve provides a friction fit between the
mounting block bore and the WS-24
™ sensor.
Please note that WS-24 ™ wheel speed sensors must use
clamping sleeve p/n 5012878 instead of p/n 5006849 (used
for previous wheel speed sensors). Always use correct
clamping sleeves to avoid problems associated with reduced
retention force, such as sensor movement and resulting
ABS trouble codes.
The friction fit allows the WS-24 ™ sensor to "slide" back
and forth under force but to retain its position when the
force is removed.
When the WS-24 ™ sensor is inserted all the way into the
mounting block and the wheel is installed on the axle, the
hub exciter contacts the sensor, which pushes the sensor
back. Also, normal bearing play will "bump" the sensor away
from the exciter. The combination of these two actions will
establish a running clearance or air gap between the sensor
and exciter.
FIGURE 4 - SPEED SENSOR VOLTAGE CYCLE OUTPUT
PEAK TO PEAK
PEAK TO PEAK
HIGH SPEED
LOW SPEED
TECHNICAL INFORMATION
Electrical connector 2 Pin.
Sensor resistance 1500-2500 ohms
Output voltage At a minimum of 100Hz
(approximately 7 mph) the sensor
output across the leads should be
0.400 VAC.
Sensor gap 0 to 0.015 inch.
Sensor body Outer diameter is 0.627 inch.
Normal resistance 1500-2000 Ohms.
range across pins (Note: Previous model WS-20 ™
at room temperature sensor was rated at 2000-2500
Ohms.)
FIGURE 5 - TYPICAL ANTILOCK SYSTEM
FIGURE 3 - CLAMPING SLEEVES
P/N 5006849
P/N 5012878
CORRECT
CLAMPING
SLEEVES
HAVE “BX” IN
A SWOOSH
SYMBOL
PREVIOUS
CLAMPING
SLEEVES HAVE
“BW” IN A
DIAMOND