Davis Instruments DriveRight 600E VSS, Руководство по установке

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12
Troubleshooting
If your speed is not registering correctly, consult the following check
list to help you identify the cause of the problem.
• Make sure the display is reading in the units (km/hr or mph) you
expect.
• Hold down the Set/Clr button in the Current Screen to change the
units.
• Make sure the unit has been calibrated correctly.
• Check the calibration section of the DriveRight 600
E
User’s Guide.
• Check the switch settings on the VSS in-line circuit and reset the set-
tings if necessary.
• See “Configure the VSS Signal Settings” on page 10.
• Double check your power and ground connections using a
multimeter.
Note: Remember that BAT, which means that the console is currently using battery
power, will not be visible on the display if the DriveRight is connected to the
harness cable and rec12 VDC from the vehicle.
• Make sure the VSS wire is correct.
If the green test LED of the VSS in-line circuit does not flash at low
speeds, you may not have the correct wire (switch 4 must be on to
enable the test circuit).
The following other methods can be used to see if you have the cor-
rect wire. In order of preference:
• Use a portable oscilloscope and verify the square wave or sine
wave VSS signal. Watch the signal frequency change with speed.
• Use a multimeter to measure the frequency of the VSS pulse.
Usually, the PPM (pulses per mile) of the VSS signal is known.
At 40 km/hr (25 mph) the following frequencies should be:
• 2000 PPM: 14 hz
• 4000 PPM: 28 hz
• 5000 PPM: 35 hz
• 8000 PPM: 56 hz
• A voltmeter can be used on square wave signals to verify the 2 DC
levels when the vehicle is moved. Note, in most cases the vehicle
must be running and driven slowly to detect this change.
• Check with your local vehicle dealership to make sure your vehicle
is equipped with a complete VSS signal.