The Topcon AT-B2 is the most accurate Auto Level in the AT-B Series from Topcon and supersedes the previous Topcon AT-B2 model that was based on the Sokkia series of Auto Levels. There are 3 models in the Topcon AT-B range, the Topcon AT-B4A, the Topcon AT-B3A and the Topcon AT-B2.
Topcon describe the AT-B series of Auto levels as durable, dependable, high value auto levels. They all share the same type of compensator, the ultra short focusing and protection from the harshest of weather.
Setting up the Topcon At-B2 is straightforward and easy. Just setup your survey tripod (either the aluminium or wooden type) relatively level, on sturdy ground and securely fasten the Topcon AT-B2 to your tripod and use the three adjusting screws and the circular levelling vial to bring it into the compensator’s operating window. The Topcon AT-B2 has a pendulum compensator and consists of four suspension wires made from a super high tensile metal and a magnetic damping system. This construction provides durability and accuracy of the compensator system over a wide range of temperatures. The compensator works over a range of 5 degrees from the horizontal plane, ensuring that even the slightest inaccuracy in the levelling vial is accounted for. The Topcon AT-B2’s compensator is more finely tuned than that of the AT-B3A or AT-B4A with a setting accuracy of just 0.3 seconds (angular measurement). Another advantage of this system is that vibrations from nearby heavy construction plant are quickly overcome allowing readings to be taken once more.
The Topcon AT-B2 has a very short focusing ability. Reading a staff from just 200mm away is far better than any other auto level from other manufacturers. This is a handy advantage when working close up, or wanting to be close to a datum point. The Topcon AT-B2 has a magnification of 32times and the field of view is a wide 1 degree and 20 minutes. The image is erect (staff is viewed upright) and there are also the stadia marks on the cross hairs to allow for distance readings to be taken from the staff. These stadia marks are set at the standard 1:100 ratio. The focusing on the Topcon AT-B2 is a dual speed adjustment, different to the AT-B3A or the AT-B4A. It also has a horizontal circle for angle measurements to the nearest degree, it is free to rotate so that angles can be easily read from a zero datum.
The Topcon AT-B2 has a rating of IPX6 which means that it there is no data available on dust protection but it is protected from powerful water jets (a test that lasts for 3minutes using 100 litres every minute). This protection helps prevent condensation forming inside the telescope.
Accuracy for a 1km double run levelling run is quoted by Topcon as being 0.7mm for the Topcon AT-B2. There is an optional micrometer available to increase the accuracy quoted for the Topcon AT-B2. This would enable an accuracy of 0.5mm for a 1km double run levelling exercise.