All about optical levels

Optical (optical-mechanical) level (level) is a device practiced in geodetic and construction work, which makes it possible to detect the difference in height between points on a plane. In other words, this device allows you to measure the unevenness of the plane you require and, if necessary, level it.

The structure of the overwhelming mass of optical-mechanical levels is similar and differs mainly in the presence or absence of a rotary flat metal ring (dial), which makes it possible to recognize angles on a horizontal surface with an accuracy of 50% and features in the design of some components. Let's analyze the structure and how the ordinary optical layer functions.

The basic element of the device is an optical (telescope) tube with a lens system, capable of showing objects of observation in an enlarged view with a magnification of 20 times or more. The pipe is fixed on a specialized rotating bed designed for the following:

• fixation on a tripod (tripod);
• setting the optical axis of the device to an exact horizontal position, for this purpose the bed is equipped with 3 vertically adjustable "legs" and one or 2 (in samples without automatic adjustment) bubble levels;
• accurate horizontal guidance, which is done by paired or single flywheels.

Adjustment to the user's vision is carried out by turning the adjusting ring on the eyepiece. If you look into the eyepiece of the telescope of the device, you can see that, in addition to enlarging the observed object, the device applies a scale of thin lines (reticle or reticle) to its image. It creates a cruciform pattern from horizontal and perpendicular lines.

In addition to the device itself, for measurements we need the above tripod, as well as a specialized calibrated rod for measurements (measuring rod). The divisions are 10 mm wide stripes of alternating red and black. The numbers on the rail are located with a difference between 2 adjacent values ​​of 10 centimeters, and the value from the zero mark to the end of the rail in decimeters, at the same time the numbers are shown in 2 digits. So, 50 centimeters is marked as 05, the number 09 means 90 centimeters, the number 12 is 120 centimeters, and so on.

For comfort, the 5-centimeter marks of each decimeter are also connected with a perpendicular strip, so that absolutely the entire rail is marked with symbols in the form of the letter "E", straight and mirrored. Old modifications of levels transfer an inverted picture, and a special rail is needed for them, where the numbers are inverted. The device is accompanied by a technical passport, which certainly indicates the year, month, the date of its last verification, calibration.

For the optical-mechanical levels, GOST 10528-90 was created, which contains information about the devices, key characteristics and types, technical specifications and methods of checks. In accordance with GOST, any optical-mechanical level belongs to one of the appropriate classes.

• High precision. The root mean square error of the adjusted value per 1 kilometer of travel is not more than 0.5 millimeter.
• Accurate. The deviation is no more than 3 millimeters.
• Technical. The deviation is no more than 10 millimeters.

Tripods for instruments are made, as a rule, of aluminum, since this metal has a low mass, but at the same time has a high strength. These characteristics have a positive effect on the transport comfort of the equipment. Besides, the material for the tripods is wood, however, their price is higher, however, the stability is more reliable... Small mini tripods are made mainly of fiberglass. The devices themselves must be of high strength. In this regard, for the production of high-quality samples of the case, mainly metal or specialized plastic is used. Setting details, for example, screws can be made of plastic or metal.

Taking into account the type of device, as well as the material from which it is made, the approximate weight can be from 0.4 to 2 kilograms. Optical-mechanical samples weigh approximately 1.2 - 1.7 kilograms. When using auxiliary equipment, for example, a tripod, the weight increases to 5 kilograms or more. Approximate dimensions of the optical-mechanical levels:

• length: from 120 to 200 millimeters;
• width: from 110 to 140 millimeters;
• height: from 120 to 220 millimeters.

The main principle used in the design of all types of devices is the transmission of a horizontal beam to the distance required for its actual use. This principle is used through the implementation of the correlation of geometric conditions and a set of technical means for transmitting information in the form of an optical signal in the level structure.

If we compare the optical-mechanical device with other similar devices of different types, then it has a fairly large number of positive qualities. The most important of these is an acceptable price-quality ratio. The device has a relatively low price, however, it is characterized by good accuracy. An additional plus is the presence of a compensator (not for every device), which constantly monitors the optical axis in a horizontal position.

The optical tube assists in the correct aiming at the subject of the shooting. The liquid level makes it possible to keep the orientation of the device under control during measurements, which allows you to determine the correctness of measurements on the spot. The main advantage of the device is the ability to use it at fairly large distances. Accuracy does not deteriorate at all with an increase in the measuring distance.

The disadvantages of the device can be attributed to its operation in the presence of 2 people. Only under such conditions is it possible to find out the correct data. In addition, the disadvantages include a stable check of the optical-mechanical device, or rather, its working position. This device needs constant monitoring by means of a level. Another small drawback of the device is its manual alignment.

According to experts, the best optical-mechanical level is BOSCH GOL 26D, which stands out for its high quality workmanship and excellent German optics. Provides high quality images and high measurement accuracy. In addition, such samples were included in the rating.

• IPZ N-05 - a precision model, which is used in the course of geodetic surveys and tests, if increased requirements are imposed on the result.

• CONDTROL 24X - a popular device for accurate and fast measurements. Practiced during construction and renovation activities. Equipped with 24x zoom, which makes it possible to work on large areas. At the same time, the device guarantees extremely correct data - a deviation of no more than 2 millimeters per 1 kilometer of the average elevation.

• GEOBOX N7-26 - an excellent solution for operation in open areas. It stands out for its high resistance to mechanical stress, moisture and dust. Provides a clear picture, has an efficient optical system.

• ADA instruments Ruber-X32 - a good optical device with a rubberized housing for use in a wide variety of weather conditions. Equipped with reinforced threads to reduce damage from falls. The package includes a specialized cover screw for securing the expansion joint during transportation. Ensures precise aiming and an integrated pre-sight viewfinder.

The main step in buying an optical-mechanical level should be the study of the market for construction and geodetic devices that meet the required characteristics and working conditions. The following describes the main aspects of choosing the right device from the extensive assortment list available.

• Often, the first aspect of the choice is not the functionality of the device, but its price. Focusing on the most budget-friendly modifications, the consumer runs the risk of purchasing a low-quality device with the smallest set of options and unreliable measurement accuracy. The optimal ratio of price and quality in most cases is acceptable.
• Level configuration and the need for the presence of a compensator in it. The compensator is a free-hanging prism or mirror in the optical system to maintain the horizontal line of the hairline when the device is tilted within the specified range. The damper dampens accidental or externally initiated swinging of the compensator. When buying a device with a compensator, it is not so much the peculiarities of its structure, among which there are really original technical solutions, that the quality of their implementation by the manufacturer is of no small importance.
• The quality of parts and workmanship. A feature of the optical-mechanical device is that there is nothing especially to break in its structure. A manufacturing defect, if any, will be detected during the first measurements and the device will be replaced. Renowned companies guarantee the excellent quality of their own products, expressing this in the price of the product. When buying at a retail outlet, it is necessary to check the smoothness of the adjustment of the guide screws and immediately get the support of a highly qualified specialist.
• Accuracy, multiplicity and other technical parameters again depend on the type of future work. Optical and mechanical levels with an integrated compensator and a magnetic vibration damping system are considered to be more accurate.
• When buying a device, it is necessary to find out whether there is a verification certificate (when, in fact, it is required), since sometimes the price of the verification operation is included in the final price of the device, making it more expensive accordingly.
• When buying a device from one of the popular brands, it will be useful to find out the location of the nearest organization providing service support and maintenance services.
• The availability of legible and detailed technical documents on the settings and does not cause problems in using the device.

The work is performed by 2 people: one - specifically with the device, placing, pointing at the object - a ruler, reading and entering values, and the other with a measuring rod, dragging and placing it according to the instructions of the first, observing its perpendicularity. The first step is to find a place to install the device. The most suitable location is in the center of the area to be measured. A tripod is placed on the selected area. To obtain a level horizontal position, loosen the tripod leg clamps, mount the tripod head to the required height and tighten the screws.

The level is placed and fixed with a fixing screw on a tripod. Turning the lifting screws of the device, using the level, you need to achieve the horizontal positioning of the level. Now you need to focus on the object. To do this, the telescope must be aimed at the staff, turning the handwheel to make the image as sharp as possible, the sharpness of the reticle is adjusted with the adjusting ring on the eyepiece.

After installing and configuring the device, you can start exploring. The rod is placed on the starting point, the readings are carried out along the middle thread of the telescope mesh. The readings are recorded in the field book. Then the staff moves to the measured point, the process of reading the readings and registering the count is repeated. The difference between the readings of the initial and measured points will be the excess.

For information on how to use the optical level correctly, see the following video.