Fluke 125
Users Manual
A-4
1: Ch. A (+)
4
3: COM (-)
2
5
M12 CONNECTOR (FEMALE)
CAN Bus/DeviceNet
The Controller Area Network (CAN) is used on board of
automobiles and also in industrial applications. The
industrial bussystem DeviceNet is based on CAN
hardware. CAN is a two-wire differential bus used to
control actuators and to read out sensors. The bus allows
data exchange between different devices. The signal
behavior in time is shown in the figure below. The signal
wires are marked CAN_L and CAN_H. There is also a
common (reference wire) CAN_GND. Data traffic is
continuous. Each of the CAN bus lines can be in either
two logical states: recessive and dominant. The state
changes occur on both wires simultaneously. The voltage
level for recessive (logical 1) is 2.5 V for both bus lines.
The voltage level for dominant (logical 0) is 3.5 V for
CAN_H and 1.5 V for CAN_L.
3.5 V
2.5 V
1.5 V
CAN_H
Connect
to Ch. A
CAN_L
Connect
to Ch. B
Ground
Connect
to COM
0 V
To check CAN Bus, ScopeMeter Channel A and B are on
and DC coupled. The recommended probes are STL120
(1:1). Probe Tip A must be connected to CAN_H, B to
CAN_L, and COM to CAN_GND.
Bus lines can be reached with Back Probe Pins at screw
terminals at a device’s wire entry point: wire colors
commonly used are white for CAN_H, blue for CAN_L,
and black for CAN_GND.
Alternatively you can use a third party DB-9 to 4 mm
banana breakout box. In addition the figure below shows
the pinning of a DB-9 female connector and a typical
Automotive (OBD2) connector. Bear in mind that some
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