DAF CF65, CF75, CF85 Series . Manual — part 495
5
CF65/75/85 series ≥0E621376
General
COMPONENTS
1-1
1. GENERAL
1.1 MULTIMETER
Various measurement options can be selected
on the Fluke 87 multimeter.
Units of measurement
The multimeter should be set to the range for
the unit of measurement required.
For example, voltage range, current range, or
resistance range.
The units of measurement are indicated by
symbols on the meter. The following symbols
are used:
1.
DC voltage
2.
AC voltage
3.
DC current
4.
AC current
5.
Resistance
6.
Duty cycle
7.
Frequency
DCV - V
ACV - V
DCA - A
ACA -A
Ohm -
%
Hz
1
2
3
4
5
6
7
W 5 01 004
2
200404
5
COMPONENTS
General
CF65/75/85 series ≥0E621376
1-2
1.2 SCOPEMETER
Diagnostics in modern electronic systems is
becoming steadily more complex.
Using a multimeter on its own is not always
sufficient to diagnose a fault.
The scopemeter allows complex signals to be
measured.
Practical examples of complex signals are:
-
PWM signals
-
signal deformation
-
CAN-bus-signals
2
200404
5
CF65/75/85 series ≥0E621376
General
COMPONENTS
1-3
1.3 SIGNAL MEASUREMENTS
Sine--wave signal (AC voltage)
This signal changes polarity regularly in relation
to the “0” line.
Frequency
The frequency is shown in Hertz (Hz).
The number of complete sines per second is the
frequency of the signal (3 Hz in the diagram).
Voltage
If the number of sines per second increases, not
just the frequency increases but also the
voltage.
Measuring a sine wave signal
The sine wave signal can be measured in the
following ways using a multimeter:
-
Multimeter in the frequency position (Hz).
This measures the number of complete
sines per second.
-
Multimeter in the AC voltage position.
This measures the average value of the
supplied voltage.
Sine wave signals in the vehicle
-
Wheel speed sensor output signal.
-
Engine speed sensor output signal.
+
-
+
-
t
1
2
3
+
-
W 5 01 002
0
0
0
2
200404
5
COMPONENTS
General
CF65/75/85 series ≥0E621376
1-4
Square wave signals
Square wave signals are signals with only two
voltage levels, both of which have the same
duration in principle (t1 is equal to t2).
If there is a difference between the duration for
the two levels (t1 is not equal to t2), the signal is
also called a ”pulse train“.
Duty cycle
The duty cycle is the ratio between the two
voltage levels, expressed as a percentage.
A
x 100%
B
The voltage level ratio of a “pulse train” may
change (for example, when the vehicle speed
increases).
If the number of pulses per unit of time
increases, the duty cycle reading will rise.
Voltage
An increase in the number of pulses per unit of
time will not only lead to a higher duty cycle ratio
but also to a higher mean voltage.
+
0
t
2
t
1
t
2
0
+
A
B
0
+
t
1
0
+
A
B
W 5 01 001
2
200404
Нет комментариевНе стесняйтесь поделиться с нами вашим ценным мнением.
Текст