Installation guide

Page 12
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.
❏ Using a multimeter to measure the fre-
quency of the VSS pulse. Usually, the PPM
(pulses per mile) of the VSS signal is
known. At 40 km/hr (25 mph) the follow-
ing 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 the vehicle make and model is
equipped with a complete VSS signal.
A PPENDIX 2: VSS C OMPATIBILITY
The DriveRight can work with many different VSS signals pro-
vided the switch settings of the VSS in-line circuit are set cor-
rectly. However, if the signal does not meet the specifications
below it may not work.
❏ Maximum VSS frequency at 25 mph is 1 khz
(144,000 PPM).
❏ Minimum peak to peak amplitude at 5 mph is
1 volt.
❏ Maximum peak to peak amplitude is 25 volts.
❏ Input Impedance of VSS inline-circuit is 22k.