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APPENDIX D: HIGH SPEED DIGITAL INPUT INSTALLATION & SETUP
PURPOSE
This document describes the process of installing an RS4000 system using high speed digital inputs and calibration
using the Diagnostic Viewer Utility for your Road Safety 4000 system.
HIGH SPEED DIGITAL INPUT INTERFACE
The Road Safety system can acquire vehicle speed and engine RPM by measuring the frequency of digital pulses
which are typically generated by the vehicle computer or by sensors in the engine if a direct link with the vehicle
computer network is not available or not supported. The system uses scale values that vary with each vehicle
model and allows these frequencies to be converted directly into a speed or RPM value.
ENGINE RPM SCALE VALUES
The scale value for engine RPM is typically related to the number of pulses per revolution, which is related to the
number of engine cylinders. This number is multiplied by 1000 to provide higher precision options for calibration.
For example, the expected scale value for a 10-cyclinder Ford E-Series is 10,000. As another example, a late model
International Terrastar with a V8 turbodiesel engine uses an expected scale value of 24,000.
VEHICLE SPEED SCALE VALUES
A vehicle typically has a rated value for pulses per mile on the signal that the RS4000 reads for speed. For example,
in most Fords, this value is 8,000 pulses per mile. In a late model International Terrastar, this value is 29,500
pulses per mile. This value is used directly as the scale value for vehicle speed.
CALIBRATING SPEED AND RPM SCALE VALUES
For a variety of reasons (including inevitable differences between a vehicle’s actual speed and its reported
speedometer value as well as slight unit-to-unit variations in the RS4000’s frequency measuring capabilities), the
expected scale values used for speed or RPM will often not produce the most accurate possible speed or RPM
readings. And for these reasons, each vehicle/RS4000 combination must be individually calibrated during
installation for the highest accuracy in reporting speed and RPM.
The calibration process is done using the Diagnostic Viewer Utility to tell the RS4000 the actual current speed or
RPM value as read by the installer from the vehicle’s speed or RPM gauges. The RS4000 uses the provided
speed/RPM value along with the currently measured frequency value on the corresponding high speed digital
input to calculate the appropriate scale value.
Use the following steps to calibrate the Diagnostic Viewer Utility:
1.
Starting the Diagnostic Viewer
Begin by opening the Diagnostic Viewer Utility and connecting it to the target RS4000 unit.
Press the green triangle Start button at the top left corner of the window if the computer running the
Diagnostic Viewer Utility and the RS4000 unit are connected to the same network.
If the Diagnostic Viewer Utility is being run locally on the RS4000 unit, you must change the settings
to disable Auto Discovery and to set the host value to 127.0.0.1 before pressing the Start button.
The following screenshot shows the main screen of the Diagnostic Viewer Utility after it has been
connected to the target RS4000 unit.
