USB Autoscope IV – Operation Manual
4. Preparing the device for use
The device connects to a laptop or PC's USB port using a USB 2.0 A/B interface cable.
The computer must have Microsoft Windows XP SP2 or higher operating system and have
the USB Oscilloscope software installed.
Before the measurements, the black alligator clip from the USB Autoscope IV's power
supply cable must be connected to vehicle ground on the diagnosed vehicle. The preferred
connection point is a vehicle body ground on the diagnosed vehicle. If an older vehicle,
use the engine ground. The signal measurements on the analog inputs are relative to vehicle
ground, because the vehicle ground is connected to the common ground of the device
through the black alligator clip of the power supply cable. Note that in some cases signal
ground and ground of vehicle body are not at the same potential. One example would be
Lambda or Oxygen sensor ground on GM vehicles. This can skew voltage readings
if not taken in to account. In such cases a differential mode can be used, connect one channel
to the signal and another channel to the signal ground.
To provide power for the transducers connected to the inputs of the USB Autoscope IV,
the red alligator clip of the power supply cable must be connected to the positive terminal
of the vehicle battery.
The device and it's cables must be placed as far as possible from the high voltage wires
of the ignition system, the exhaust manifold, and the cooling system fan.
The computer itself must be grounded using a separate multi stranded copper wire
with a cross section of more than 0.5 mm
2
, otherwise a failure of the computer or device
is possible. If a laptop running on its internal battery and with the main power supply
disconnected is used, this requirement is unnecessary.
In order to avoid distortion and / or damage to the data that are sent via the USB interface,
due to electromagnetic interference from the vehicle's ignition system, it is recommended
to ground the USB Autoscope IV using a separate multi stranded copper wire with
a cross section of more than 0.5 mm
2
.
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