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H03003 - How do I calibrate my RAC-100/RAC-200?
In order to accurately measure distance, your RAC-100/200 must know the exact
distance that the vehicle will travel based on pulses from the vehicle's transmission.
The calibration number is the automatic calculation that represents the number of
pulses received over a set distance. This number, once calculated, will remain
accurate for any instrument requiring a calibration factor until a change to the
vehicle occurs, such as different size tires put on the vehicle, tire wear, air added to
the tires, etc. At that time, you must re-calibrate.
In order to calculate the calibration number for your particular vehicle, you must first establish a calibration
course. The length of the course can be any known distance more than 500 feet — 1000 feet is ideal. In general,
a shorter more precise course is better than a longer imprecise course. Your course should be straight and
accurate, so take the time to measure the course using a 100' tape. Mark the beginning and ending points so
they can be seen from inside your vehicle. Remember, the course length can be any accurate distance over 500
feet, so for convenience you could use a telephone pole or other marker as reference point.
Step 1
Slide the ON/OFF switch to ON. Your DMI will perform a brief Self Test. The current Calibration Number will be
displayed for approximately three seconds, then [C.H 0.000] will appear with the decimal between the C & H
flashing.
Step 2
Align your vehicle to the marker at the beginning of the course using a reference point on or in the vehicle, such
as a window post, door handle, your shoulder, etc.
Step 3
Press the UNIT key to select feet. The FEET LED will come on and [ 0 ] will be displayed.
Step 4
Press the CAL key. [CL 0] will show up. The instrument is asking for the Course Length. Key in the length of your
calibration course in feet using the numeric keypad and press the ENTER key. [C.H 0] is again on the display.
Press the C-HOLD key, C.H will go off.
Step 5
Drive the calibration course. The count you see represents the pulses seen from your transmission sensor and
not the distance being traveled, so don't panic when the display doesn't equal the actual length of your course.
Step 6
When you reach the end of the course, stop your vehicle so that you are exactly aligned with the end marker
using the reference point on the vehicle used at the beginning of the course Press the C-HOLD key and C.H
along with the pulses counted will be on the display. Press the CAL key and CF along with the computed
calibration number will be displayed. Record this number for future reference. Press the ENTER key. Your
calibration number is now stored in the DMI's nonvolatile (permanent) memory and [C.H 0] is displayed. The
calibration number will stay in memory for more than 40 years until you re-calibrate or manually change the
calibration number. You are able to view the current number every time you power on the DMI.
You should rerun the calibration course to verify the calibration for your vehicle. Press C-HOLD prior to
measuring. If this is the first time you have calibrated a DMI, you may want to run the course a couple of times to
practice being properly aligned when starting and stopping at the course markers.
The calibration number used should be between .500 and 1.200. If your calibration number is below this range,
you need to use a higher division factor (such as 1 to 16 or 1 to 32) by adjusting the rotary switch on your MDS.
Of course, if the calibration number is too high, use a lower division factor (such as 1 to 1 or 1 to 2). Several
calibration runs may be necessary to determine which division factor is best for your vehicle.
Refer to How do I adjust the Vehicle Speed Sensor Pulse Rate? for more information on this adjusting the rotary
switch.
H03003 - How do I calibrate my RAC-100/RAC-200?
In order to accurately measure distance, your RAC-100/200 must know the exact
distance that the vehicle will travel based on pulses from the vehicle's transmission.
The calibration number is the automatic calculation that represents the number of
pulses received over a set distance. This number, once calculated, will remain
accurate for any instrument requiring a calibration factor until a change to the
vehicle occurs, such as different size tires put on the vehicle, tire wear, air added to
the tires, etc. At that time, you must re-calibrate.
In order to calculate the calibration number for your particular vehicle, you must first establish a calibration
course. The length of the course can be any known distance more than 500 feet — 1000 feet is ideal. In general,
a shorter more precise course is better than a longer imprecise course. Your course should be straight and
accurate, so take the time to measure the course using a 100' tape. Mark the beginning and ending points so
they can be seen from inside your vehicle. Remember, the course length can be any accurate distance over 500
feet, so for convenience you could use a telephone pole or other marker as reference point.
Step 1
Slide the ON/OFF switch to ON. Your DMI will perform a brief Self Test. The current Calibration Number will be
displayed for approximately three seconds, then [C.H 0.000] will appear with the decimal between the C & H
flashing.
Step 2
Align your vehicle to the marker at the beginning of the course using a reference point on or in the vehicle, such
as a window post, door handle, your shoulder, etc.
Step 3
Press the UNIT key to select feet. The FEET LED will come on and [ 0 ] will be displayed.
Step 4
Press the CAL key. [CL 0] will show up. The instrument is asking for the Course Length. Key in the length of your
calibration course in feet using the numeric keypad and press the ENTER key. [C.H 0] is again on the display.
Press the C-HOLD key, C.H will go off.
Step 5
Drive the calibration course. The count you see represents the pulses seen from your transmission sensor and
not the distance being traveled, so don't panic when the display doesn't equal the actual length of your course.
Step 6
When you reach the end of the course, stop your vehicle so that you are exactly aligned with the end marker
using the reference point on the vehicle used at the beginning of the course Press the C-HOLD key and C.H
along with the pulses counted will be on the display. Press the CAL key and CF along with the computed
calibration number will be displayed. Record this number for future reference. Press the ENTER key. Your
calibration number is now stored in the DMI's nonvolatile (permanent) memory and [C.H 0] is displayed. The
calibration number will stay in memory for more than 40 years until you re-calibrate or manually change the
calibration number. You are able to view the current number every time you power on the DMI.
You should rerun the calibration course to verify the calibration for your vehicle. Press C-HOLD prior to
measuring. If this is the first time you have calibrated a DMI, you may want to run the course a couple of times to
practice being properly aligned when starting and stopping at the course markers.
The calibration number used should be between .500 and 1.200. If your calibration number is below this range,
you need to use a higher division factor (such as 1 to 16 or 1 to 32) by adjusting the rotary switch on your MDS.
Of course, if the calibration number is too high, use a lower division factor (such as 1 to 1 or 1 to 2). Several
calibration runs may be necessary to determine which division factor is best for your vehicle.
Refer to How do I adjust the Vehicle Speed Sensor Pulse Rate? for more information on this adjusting the rotary
switch.
