| record number: | 70 |
| instrument type: | modular electronic distance meter |
| manufacturer: | Kern |
| serial number: | 283022 |
| model: | DM502 |
| weight: | 1.62 kg |
| dimensions (l/w/h): | 17/8/19 cm |
| year of manufacture: | 1983 |
| type of distance meter: | phase-shift principle, middle range |
| precision: | 3 mm; 5 ppm |
| range: | 1200 m with single prism; 2000 m with three prisms |
| time of one measurement: | 8 seconds |
| distance reading: | digital, on the display – 6 digit number |
| light source: | infrared semiconductor GaAs diode |
| carrier wave: | 0.860 μm |
| measurement frequency: | 14.9854 MHz |
The modular electro-optical phase distance meter was made in 1983. The distance meter cannot be used on its own, as it should be attached to the telescope of some of the Kern theodolites such as DKM2-A, K1-M, E12. The distance meter has a precision of 3 mm; 5 ppm and a range of 1.2 km. The time required for one measurement is 8 seconds.
The special feature of the Kern DM series distance meters is the biaxial optics. Transmitting and receiving optics are separated. This design requires the use of the original reflectors, which have significantly larger elongated reflecting prisms.
The instrument is in the same condition as when it was originally taken out of service and is still functional.