By Radu Motisan Posted on December 8th, 2009 , 1455 Views (Rate 1.15)
I've just received a very nice and compact russian dosimeter, the Terra-P, purchased from Ebay.
It came with a nice leather case, manual and good quality batteries. It is easy to use, and quite sensitive. The background radiation in my location is 0.11uSv/h .
This dosimeter can measure gamma radiation from 0.1uSv/h up to 999.9uSv/h . Besides this dose rate, it also features a dose measurement, a clock and alarm triggered by unsafely high levels of radiation.
It can measure Beta rays if the Geiger Muller cover is removed, but also x-rays (tested with a DY86 rectifier tube, more on this later).
Press shortly the MODE button to switch the dosimeter on.
Use the THRESHOLD button to run the programmed threshold level and change its value. At excessive threshold level the dosimeter will alarm about hazard (by default, the preset threshold value is 0.30 µSv/h, an average permissible radiation level for premises). Zero the previous measurement results by the THRESHOLD button.
Note. In case of natural (c 0.1 µSv/h) gamma radiation background, an ED change by one low-order digit occurs on the display in 10 hours, and the "0.001 mSv" result, equal to 1.0 µSv, is shown on the digital indicator.
Download the English manual here.
To read more on radiation measurements, you can also see this Wikipedia article on the Sievert.