The Terratrip 202 Plus – A Good Basic Odometer

A couple of weeks ago I posted a report on this website about adding a Terratrip speedometer cable wheel sensor onto a speedometer cable.  This weekend I added the external mounted speedometer cable to our Subaru Outback in order to connect and test my Terratrip 202 Plus odometer.  I want to demonstrate the use of this odometer for a project that I am working on related to the Nevada Open Road Challenge.

The Terratrip 202 Plus odometer is a good basic odometer that is a capable odometer and is easy to use.  These units are commonly used in stage rally cars where due to the use of stage notes, a basic odometer will serve quite well.  A nice feature of this odometer is that the movable portion of the buttons on the Terratrip 202 Plus are located below the “skin” of the face of the unit and, as such, are well designed to meet the harsh dust and weather conditions that can occur in stage rallying.

Terratrip 202 Plus (1)

The Terratrip 202 Plus Rally Odometer

The Terratrip 202 Plus has two displays in the odometer mode.  The upper display shows the total distance, while the lower display can be used for showing the incremental distance.  The numbers are large and easy to read on the Terratrip 202 Plus and I’ve never had a problem reading the distances regardless of how rough the roads were.

Terratrip 202 Plus (8)

The Top Display Can Display Total Distance While Lower Display Can Show Incremental Distances

The Terratrip 202 Plus has a great of flexibility in that it is possible to hook up two probes or sources of pulses for the purposes of measuring distance.  In addition, it is possible to have two different calibration values with each probe.  This allows for the co-driver or navigator to have one calibration value for gravel stage roads and paved transit roads.  The two probes feature allows for a backup probe should one be damaged during the rally.

The Terratrip 202 Plus has a “Freeze” button which I have found to be useful when checking on the unit’s calibration on the fly during a rally when there is no time to stop or when recording a distance to a particular position while on the fly.

Terratrip 202 Plus (7)

The Terratrip 202 Plus Uses a Pulse Count For Calibration

The Terratrip 202 Plus uses a four digit calibration number which is the number of pulses per mile or pulses per kilometre, depending upon the units used in the rally.  The speedometer cable sensor that I installed generates two pulses per revolution.  In my short test drive around my neighborhood, I just did a rough calibration on the fly using the speedometer and the value I used was 1500 which would be equal to 750 wheel rotations per mile.

To explain the significance of a four digit calibration figure consider the example in my photo above.  The maximum precision error of the odometer calibration is based on one-half of the calibration interval.  In the case above suppose if the required calibration number was 1500.5 pulses per mile.  However the four digit calibration number can only be 1500 or 1501, the navigator can not enter 1500.5.  The navigator has to choose either 1500 or 1501.  This illustrates the concept of calibration precision of this, or any other, odometer.  In the example presented, the maximum error would be 1/3000 or 0.01 km every 30 km.  For many rally events, a four digit calibration value based on pulses is satisfactory.

Terratrip 202 Plus (6)

The Terratrip 202 Plus Can Show The Vehicle Speed On The Bottom Display

By pushing the “Speed” button, the lower display will show the vehicle’s speed.  I found this to be very useful during stage rallies where many of the cars where I was the co-driver had non-functioning speedometers or no speedometer at all and the speed display on the Terratrip 202 Plus kept us from getting speeding tickets on transits.

Terratrip 202 Plus (10)

The Connection Details Are Shown On The Back Off The Odometer

The Terratrip 202 Plus odometer has been around for a long time.  They can be bought relatively inexpensively from owners of worn-out stage rally cars.  I bought mine about ten years ago from a fellow out west who said that this particular odometer had been used to help layout the 2002 Winter Olympics in Salt Lake City about 13 years ago.  I have not used this particular unit much, but I loaned it to Bob Vogel, who lives not too far from me, for use in the 2012 Alcan 5000 Winter Rally.

The details of installing and using the Terratrip 202 Plus, as well as other older Terratrip odometers are included in the following file: Terratrip Manual 2011

For anyone who needs just a basic calibratable odometer, the Terratrip 202 Plus should fit the bill.

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