As measurement tools, belonging to the general classification of odometers, particularly manual odometers, wheel odometers, topometers or measuring wheels are very useful for, among others, engineers, architects, contractors, surveyors, builders, appraisers, budgeters, real estate agents and anyone interested in measuring long distances in a short time. To use them, simply reset the counter, place the wheel at the point where you want to start measuring, move it in a straight line to the desired point and read the counter.
In most cases, the odometers are not designed to be extremely accurate, but they are designed to give a very good estimate. There are also special odometers, for example for surveyors, which work perfectly in terrain elevations, or those used by railway workers, provided with an adapter with metal side plates to fit into the rails.
However, beyond the variants, there are basically two types of odometer to choose from: mechanical and electronic. This refers to the mechanism used to make the measurements and the way the results are presented.
The mechanical odometers use the typical mechanism of car odometers, that is, a system of graduated wheels interlocked, which successively mark the distance traveled every 100 meters, one kilometer, tens, hundreds and thousands of kilometers, and are displayed on a mechanical counter.
On the contrary, the functioning of the electronic odometers It is based on an electrical sensor that is usually a magnet and that with each turn of the wheel actuates a magnetic contact or a semiconductor; this, in turn, sends an electrical impulse to the electronic counter, which displays the result on an LCD screen.
When we need to acquire an odometer, the first thing will be to consider the application and the specific technical requirements of the utility that we will make of it.
The first decision we must make is whether it will be mechanical or electronic. Let’s see in which cases it is convenient for us to choose one or the other type.
They adapt to all kinds of work and, due to the simplicity of the operating mechanism, are very easy to handle. Precisely for this simplicity, they offer readings in a single type of measurement unit (either metric or imperial) and do not require any power source.
The incorporation of a backlit screen not only offers greater clarity in the readings, but also makes it possible to read in various units of measurement, whether in meters, yards, feet or inches, as well as other functions that we will see later. However, this type of mechanism needs a battery to work, and if it were to run out in the middle of work, the marking would disappear. Therefore, when starting a measurement job with an electronic odometer, we must ensure that the battery has a sufficient charge.
Other parameters to consider when buying an odometer are the following:
Odometer wheel size
The odometer offering encompasses a wide variety of wheel sizes, as small as a shopping cart or as large as a bicycle. What does this diversity of sizes respond to? Precisely to the application and environment where the instrument will be used. As a general rule of thumb, the more uneven the surface to be measured, the larger the wheel size will need to be to get the most accurate estimates.
Wheel sizes are measured by diameter and / or perimeter or circumference of the wheel. The smallest sizes correspond to wheels between 8 and 16 cm in diameter (perimeters of 0.25 m and 0.5 m, respectively). Medium-size wheels are 32 cm in diameter (1 m perimeter) and large-size wheels have a 64 cm diameter (2 m perimeter).
In this way, if we are going to measure distances indoors, that is, if we are dedicated, for example, to laying floors and carpets, laying cables or pipes or if we are real estate agents, a small wheel odometer and better yet, the models with two small wheels. For outdoor work and in flat places, such as terraces, sports fields, grounds, gardens, parks and general construction sites, it is better to choose an odometer with a medium size wheel or models with two medium size wheels or one size wheel big. And if we have to make measurements in large areas of uneven surfaces and / or in adverse weather conditions, such as rain or muddy soils, for example, in fields, farmlands, meadows and forests, then we should direct our search towards models with large wheels. .
Odometer wheel type and material
The wheels of an odometer differ not only in size, but also in other factors such as the material they are made from and the type of wheel. The most durable, stable and resistant (and most expensive) are made of steel and have spokes, like the wheels of a bicycle, which makes the tool very light. However, strong, lightweight odometers are also available with lacquered plastic wheels or ABS plastic with neoprene coating, and with die-cast aluminum wheels with rubber or neoprene coating. The neoprene allows the wheel to adapt to any terrain or surface without slipping.
On the other hand, we will also find odometers with completely solid wheels, built in steel with neoprene coating (see figure below). This particularity is especially interesting in fields, forests and terrains where branches, stakes, weeds, tall grasslands or bushes abound, which could get caught in the rays and render the instrument inoperative. In contrast, a solid wheel prevents these jams from occurring.
Measurement range and precision
Depending on the model, the measuring capacity of an odometer counter, both mechanical and electronic, can be 4, 5 or 6 digits. This means that they can measure up to the figures 9999, 9999.9 or 9999.99, respectively, in the unit (s) of measurement that we will detail below. Generally, the smallest and / or cheapest wheel models measure up to 5 digits, while the medium and large wheel models measure 6 digits.
The measuring range is also related to the precision or tolerance of the tool. These parameters range between ± 0.02%, which corresponds to a maximum error of ± 2 cm at a distance of 100 m, and ± 0.05%, which corresponds to a maximum error of ± 5 cm at a distance of 100 m. . Less accurate and therefore cheaper models can have a tolerance of ± 0.1%, that is, up to a maximum error of 10 cm in 100 m.
Therefore, the choice of one or the other model will also depend on the degree of precision we need for our work.
Odometer Units of Measure
In the United States, where imperial measurements are predominant and in other countries where both metric and imperial measurements may be required, odometer units of measure are an important factor. For this we must remember that if we decide on a mechanical odometer, we must make sure in which measurement system (metric or imperial) the meter is provided. The counters of some mechanical odometers with the metric system offer the possibility of counting up to 9999.99 meters, decimeters or even centimeters.
If instead we decide on an electronic odometer the tool can be set to alternately measure in metric or imperial units.
Odometer overall size
This detail is very important for the transport and storage of the tool, precisely when we want to reduce its size to a minimum. Many models feature a telescopic handle that extends to over 1 meter and the entire unit folds down to a size of 50cm or less when not in use. In other models, the handle is detachable.
Optional Odometer Features and Accessories
Depending on our needs, it will be useful to check if the odometer we choose has some or all of these attachments.
Carrying case: Many manufacturers offer a carrying case along with their odometers. The case will help us keep our odometer protected from dust, water and sunlight when not in use and will extend its life.
Counting Forward and Backward Button: This useful feature that many odometers incorporate allows the meter to add when the device moves forward and subtract when it moves backward, freeing us from time-consuming calculations.
Button to reset the unit: ideal for resetting. By pressing this button we can start with a new measurement.
Side stand or stand – Used to securely place the device on uneven surfaces.
Rail Adapter – This item is a must have for railway workers. It is not suitable for any model of odometer, so if this is our need, we must look for an odometer that allows us to attach an adapter for measurements on rails.
Ergonomic grip, ergonomic grip built-in brake trigger, automatic unit of measure conversion function, 4 or 8 measurement internal memory, automatic and manual shutdown, mechanical counter with built-in light and other delicacies are also available on some odometers . It’s just a matter of looking for them.
Finally, the odometer offer also contemplates the case that we are lazy and / or we have to measure very long distances. For this, there are manufacturers that offer highly accurate odometers (99.95%) that are coupled to a vehicle by means of a trailer hitch, as we see in the figure below. These trailer odometers consist of two 40 cm diameter wheels and are designed so that the measurement is carried out comfortably from inside our vehicle through a digital display. Readings can reach a whopping 9,999,999.9m, or 9999km.
As we can see, the availability of odometers is immense and based on the characteristics that we have just detailed, surely our choice will be easier.