What is the Best Value Automatic (Dumpy) Level
The Topcon AT-B4A offer the best value in the Topcon AT-B series of Automatic (Dumpy) Levels. The Topcon AT-B4A is the entry level Auto Level in the AT-B Series from Topcon and supersedes the Topcon AT-B4 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-B4A 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-B4A 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-B4A 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. Another advantage of this system is that vibrations from nearby heavy construction plant are quickly overcome allowing readings to be taken once more.
What is the shortest distance that can be seen through a Level?
The Topcon AT-B4A 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-B4A has a magnification of 24times, significantly more than other manufacturers’ base auto levels, and the field of view is a wide 1 degree and 25 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-B4A is a single speed adjustment. 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.
Can an Automatic Dumpy Level be Used in the Rain?
The Topcon AT-B4A 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.
What is the Accuracy of an Automatic (Dumpy) Level?
Accuracy for a 1km double run levelling run is quoted by Topcon as being 2.0mm for the Topcon AT-B4A. There is no micrometer available to increase the accuracy quoted for the Topcon AT-B4A.