Introduction: Our 5 senses leave us blind to a whole lot of things going on around us in the physical world. As I learned about electronics and physics, I became interested in devices that allowed us to "see" this unseen physical word. I bought or built oscilloscopes, spectrum analyzers, receivers, IR scopes, etc. Understanding my interest, someone gave me a 1950's radiation meter. I truly cherish this rare collector's item, but at the same time always wanted a more modern, portable, digital radiation meter. I scoured the surplus market for such a device, but the prices were just too high. Physical: The unit I purchased is the MKS-05 "Terra-P". This is a device about the size of a very thick mobile phone. It has 2 buttons and a simple LCD display similar to those found on low-end Digital Multimeters. Also in common with some DMM's is its yellow plastic case. The plastic is quite thick, and the unit looks durable. The back of the unit has 2 doors. One is for the battery compartment, and the other uncovers the actual Gieger-Muller (GM) tube. The door is not for replacement of the tube, it has another purpose that will be detailed below. These devices are not constructed like high-end consumer electronics. The battery door appears to be a slightly different color than the rest of the unit, and the GM tube door does not fit perfectly flush. The catch on this door also seems small and delicate. I have taken the door off many times, and it still is fine, but I feel that it may eventually fail. The two buttons are large, and must be pushed firmly to operate. The display is simple, and while there is no contrast adjustment, and no backlight, it can easily be read in almost any light. The display has 4 full digits, and a few special symbols. The symbols indicate the display units, the battery level, and the alarm function. In addition to a symbol on the display, the user settable alarm triggers a very noticeable sound on the unit's small piezo speaker. This speaker also signals clicks for radiation counts when the unit is in the "Dose Rate" mode. Operation: The MKS-05 has 4 modes of normal operation. Pressing the "Mode" button cycles through these four modes: Dose Rate ---> Dose ---> Time of Day ---> Alarm Time When the unit is powered on (By holding the "Mode" button for a few seconds), it enters the "Dose Rate" mode. I would prefer to call it the "Live Counting" mode. In this mode the unit behaves as we would expect a Gieger Counter to operate. It clicks for each detected particle, and displays the time integrated counts as microsieverts per hour (µSv/h) on the display. There is no way to select other units, however microsieverts can be converted to microrads just by multiplying by 100. If you prefer to think in rads, just ignore the decimal, and read the display as microrads. 0.15 µSv/h = 015 µrads/h It is not my intention to reproduce the owner's manual here, but I would like to spend a little more time describing this mode, because it is the most important mode for measurement of both ambient radiation, and for testing an object for radiation. When the unit is first switched on, it begins integrating counts. It displays a preliminary value in 10 seconds while continuing to integrate counts. This works very well, and the reading usually stabilizes within a few of these 10 second intervals. After 60 seconds, a sufficient sampling of the radiation level has been performed, and the display stops blinking, indicating that the displayed value is accurate. Events continue to be counted, with a ping sound for each one, and the display is updated every 10 seconds. This works very well to provide an initial assessment very quickly after power up, and to continue to display a reading that does not jump around with every natural variation in detected events, but updates fast enough to be considered a "live" reading. There is no way to mute or adjust the volume of the speaker in this mode, but this is the only mode in which the clicks are heard. The next mode is called the "Gamma Dose" mode. Think of it as accumulated dose mode. It is displayed in mSv (millisieverts) to 3 decimal places. Note that this measurement has no unit of time. It is total accumulated dose. By doing some simple math, we can see that if we are in an environment of 0.10 µSv/h, we will get our first count on this display in 10 hours (0.001 mSv = 1.0 µSv). This indication is reset if the unit is turned off. It continues to count when the unit is asleep. More on sleep mode later. The speaker does not click in this mode. The next 2 modes have to do with the built-in alarm clock. Like a simple digital watch or travel alarm, these 2 modes display the time of day, and the time the wake-up alarm is set to. The cool part about this feature is that when the alarm wakes you up, it displays the background radiation level. With the exception of the unit having no backlight, it would make a fully satisfactory travel alarm. The clock on my unit also seems to be quite good at keeping time. The speaker does not click off events in this mode, but counting does continue in the background. Even when the MKS-05 is actually turned off, the clock keeps time, and the alarm clock will wake the unit up. In addition to the simple alarm clock, there is also a radiation alarm. This is preset to 0.30 µSv/h or 0.007 mSv in a 24 hour period. This is the maximum safe level for continuous exposure. This threshold is user settable by -- you guessed it -- the "Threshold" button. (The button has other uses, such as setting the clock.) If the threshold is exceeded, the unit switches from whatever mode it is in to the "live counting" mode, the alarm icon appears, and the speaker sounds an alarm. If the unit is turned off, the threshold reverts to the pre-set value. High radiation levels will not trigger an alarm if the unit is actually off. Only pressing and holding "Mode" or the alarm clock can wake the MKS-05 if it is actually off. Momentarily pressing "Threshold" also seems to reset the unit to the "Live Counts" mode. The display will reset to 0.00 µSv/h and start flashing, just as when the unit is first powered on. I should mention that there is a very small chance of a false alarm when the unit first begins counting. If in the first ten seconds, by pure random chance, a bunch of events are detected, the unit may alarm. This has only happened once, can only happen when you are doing something to the unit, and really takes an extreme coincidence of nature. I have never had the unit give a false alarm other than that. In addition to evaluating the MKS-05 for false alarms, I also checked for susceptibility to RF radiation. Radiation detector meant to detect ionizing radiation should not register RF radiation. Poor design or construction could allow RF energy to get into electronics and cause false indications, alarms, resets, etc. To test this, I started up a GPRS session with my GSM phone, and placed it and the "Terra-P" back to back. In GPRS mode, mobile phones radiate more power than they do during a voice call, so this was a worst case test. The Terra-P continued to count normally, and was not affected by the RF at all.Some Trivia, and a Question There is a sticker under the battery compartment with something written in Ukrainian. It is a warranty warning label. The basic translation is: "Do Not Remove. Warranty." Now here's a question for you. The owners manual says that in the event of low batteries, poor contact with the batteries, or some other failure, the display may indicate "PO3P" - That's the Ukrainian letter, not the number 3. That pretty directly translates to "Low Batteries". (Thanks to all those that sent translations). Conclusion: The Ecotest MKS-05 "Terra-P" consumer radiation meter is an ideal device for checking specific items for radioactivity, as well as monitoring your environment for unseen dangers. The price on eBay may be much higher than the "street" price, but it is still a good value for the functionality of the unit, and the convenience of not having to fly to Ukraine. Benefits: - Very portable and consumer-friendly - Great battery life - LCD display is clear to see and understand