An indispensable measurement tool for outdoor construction sites is the optical level, widely used in various applications. We opportunely describe a automatic optical level in particular because they are the most versatile and, contrary to what might be assumed, they are the easiest to handle.
The great advantage of automatic optical levels is that they require a simple leveling by hand by means of screws, as we explained in the previous article and, once this is achieved, the compensator incorporated in the internal part of the instrument, it performs by itself the necessary functions to achieve a precise and stable leveling, ensuring a perfectly horizontal plane regardless of the position of the instrument.
The most frequent buyers of a automatic optical level They are professionals such as surveyors, land surveyors, foundation installers, deck and pool builders, surveyors, excavation contractors, landscapers, road builders and engineers who require exact grading every time. However, there are also hobbyists who want to make renovations in their parks, gardens or garages and who can take advantage of these instruments.
Therefore, when choosing a automatic optical level it is important to establish a priori certain parameters, such as:
- Degree of precision required, according to the type of work to be carried out.
- Required viewing distance.
- Frequency of use of the instrument (for the purposes of durability, ergonomics, etc.).
- Conditions of the terrain where you are going to work (interferences, environmental factors, such as resistance to vibration, etc.).
Consideration of these factors will guide us on the characteristics that we should look for in the instrument to choose. Among these characteristics we can highlight the following:
Accuracy / range: an instrument intended for outdoor use, such as optical levels that we are reviewing in this article, you must, in itself, have a good scope. There are jobs that, in addition to a good scope, also require an excellent precision. If these are our requirements, then we should look for instruments with a minimum range of 60 meters and an accuracy of at least 3 mm / 30 m. Naturally, these characteristics should be greater as the demands of the work to be carried out increase.
Magnification: the choice of lens magnification of a optical level it depends on the application. Thus, for example, for small or medium-scale works, which involve earthworks, drainage, green areas, concrete formwork and other works of a similar nature, a magnification between 18x and 28x will be sufficient. For general engineering works and construction projects that require greater distances and leveling standards, it is advisable to choose instruments with a magnification between 28x and 32x. For jobs that demand extreme leveling precision with the highest standards of accuracy, such as leveling industrial equipment and monitoring vertical displacement or deformation, a magnification of 30x to 34x should be available. However, we must not fall into the error of assuming that a optical level a higher magnification is better than one that offers lower magnification. Many times a high magnification power can be an obstacle, since depending on the climatic conditions, for example, waves of hot air, mist or smog can be magnified, thus making it difficult to read the staff. This means that it is always necessary to establish what is the average distance at which we are going to work and, if possible, try different devices with different magnification to decide which one offers the clearest readings of the staff from that distance.
Compensator Features: the compensator is the key component of a optical level automaticas it maintains a perfectly horizontal line of sight, even when small disturbances in the level displace the bubble from its centered position. For this reason, attention must be paid to certain parameters that characterize the compensator, for example:
- Leveling margin: most compensators provided in the optical levels They have a leveling margin, or working range, of ± 12 or ± 15 minute angle. This means that within ± 12 minutes, the compensator can correct errors of up to 4 inches above or below the crosshair on the staff at a distance of 100 feet. Within ± 15 minutes, errors up to 5 inches can be corrected.
- Damping type: generally the compensator damping is magnetic. However, those who work in environments where there is electromagnetic interference (in the vicinity of antennas, cables, motors, etc.) may require levels whose compensator has damping. by air.
- Lock button: the mechanism of blocking The compensator acts not only as a device control tool, but also for its safe transport. The locking button is located under the sight and its function is to lock the pendulums, preventing their movement when the optical level moves from one place to another. The lack of this mechanism could decalibrate and / or damage the device; hence its importance. Today the main brands of measuring instruments incorporate in their automatic optical levels the function of compensator lock.
Measurement units: In topographic measurements, the default unit for angles in many parts of the world is the gon or centesimal degree. Each quadrant is assigned an interval of 100 gon, which facilitates the recognition of the four quadrants and the mathematics that understand the perpendicular or opposite angles. Thus, 90 degrees equal to 100 gon, 180 degrees to 200 and 360 degrees to 400 gon. This speeds up mental calculations and saves a lot of time. Depending on the manufacturer, some models of optical levels come provided with units of measure in gon, so if our work involves frequent angle measurements, an instrument with a gon scale can be very useful.
Degree of protection: it is very likely that while working on a work of ours optical level be exposed to rain, dust, or even drops or bumps. Attentive to this, manufacturers design their instruments to withstand, within certain limits, this type of inconvenience. Therefore, when we go to choose, let us find out if the optical level is protected and to what degree. This grade responds to DIN standards, it is known as IP Protection Code (from English, International Protection Rating) and consists of two digits: the first (from 0 to 6) indicates protection against solid objects and the second (from 0 to 8), protection against liquid objects. When choosing a optical level, let’s make sure the protection is at least IP 54, that is, it is protected against limited ingress of dust (number 5) and against splashing water from any direction (number 4).
Accessories: As detailed above, many manufacturers sell their optical levels together with a kit that includes the main accessories, as well as others of great utility. Obviously, the more accessories that are included in the kit, the greater the convenience. These accessories are:
- Transport case: A must-have element in any kit. It offers the protection the instrument needs when not in use and provides safe conditions when it must be transported from one location to another.
- Tripod: Essential assembly element. If it is included in the kit it is an advantage because this way we can not worry about looking for one whose thread adapts perfectly to our model and brand of optical level.
- Estadal: another essential element for any optical level at the time of use.
- Plumb: The kit sold by many manufacturers includes a plumb bob to center the level relative to a point on the ground as part of the instrument leveling process. For this purpose, the plumb bob is suspended from the tripod fixing screw and the level is made to coincide with the desired point on the ground, either by moving the level on the tripod or by moving the tripod.
- Allen key and adjusting pin: Although they can be purchased separately, these resetting tools are almost always part of the kit. The allen key is the one used when we must readjust the circular level; with it we move the adjustment screws to place the air bubble in the center of the circular level, as shown in the following figure:
On the other hand, once we carry out the control of the lattice cross Following the manufacturer’s instructions, we use the adjusting pin to readjust the cross by means of a screw located in the ocular, as we see in the figure below:
In conclusion, we have listed the points to consider before buying an Optical Level, if you want to know more about this product and its technical aspects, you can continue reading in Introduction to the Optical Level.