16
Instruction book, IQAN
USB connection
This IQAN master module has an
USB interface
for communicating with the
programming software, IQANdesign and for diagnostics. A flying lead cable, 5030124
may be connected to the master module to provide an USB type B connector interface.
The connection from the module to PC can be made with a standard USB Type A male
to Type B male cable.
Connection of Parker cable 5030124 is shown below.
Connecting for USB communication.
N
OTICE
It is recommended that the two data wires,
DATA+
and
DATA-
, be a twisted pair, 15
twists/meter. Use
-VREF
for the ground connection as shown.
USB and "ground loops" (differences in ground potential)
When systems consisting of machines, modules, computers and other devices with
different ground potentials are connected by a USB cable, a ground loop may be
created. The grounds may only differ by a few millivolts, or by much more. This can be
significant when compared to the low level voltage signals that are used in USB data
transmission.
N
OTICE
Protect the PC and unit from damage due to ground loops and surges!
Ground loops can cause problems in communicating and in extreme cases the amount
of current flow can damage the USB transceiver in the PC or the module.
A recommended way to prevent ground loops is to ensure that your system includes
isolation. Isolation protects your PC from damage and preserves the integrity of your
data by physically separating the electrical connections between the PC and the unit.
Good
: Using a battery-powered laptop can prevent the formation of accidental ground
loops and short circuits. This protection only holds true, however, as long as the laptop
is not also connected to self-powered devices such as printers.
Better
: Isolation can be provided by adding an isolated USB hub between the PC and
the unit.
Best
: Use a CAN-USB interface with galvanic isolation and communicate with unit via
CAN bus. This setup is used in the automotive industry for diagnostics.
-VREF
DATA-
DATA+
IQAN master
USB type B port
